Porsche 996 C4S - cylinder lining
Discussion
The engine light came on (drive to workshop). They rang to say its misfiring on cylinder 6, they put a camera down there, noticed scorching and said the cylinder lining is deteriorating. They said it happens but cant replace one cylinder and needs a major rebuild. Either the parts/new engine depending on which works out cheaper. It drove fine but the moment the light came on, i stopped driving it.
Its my first porsche and i think my last if it is going to be this temperamental!
Its my first porsche and i think my last if it is going to be this temperamental!
Hi Chans, sorry to hear about your problem which we understand and can fix.
Firstly – statistically these failures are very rare and therefore most examples are perfectly OK. It seems a lot to us because we receive cars and engines to repair every day of the week –with one of perhaps two or three typical problems - but taken overall – Country wide - there are relatively few.
Any engine that is driven to its limits will eventually fail one day and when it does it will always find the weakest part of the chain to fail first (or there may be a few weak links). The lighter the internals are made and/or the higher the power output or revs and/or the lower the production costs – in most cases the sooner such an engine driven to its limits will find those weak areas.
These engines have excellent outputs and light weight internals and have been manufactured by more modern (and in many areas lower cost production) methods than earlier Porsche examples – but this does not automatically make them inferior – just pushes the envelope or limits nearer to daily operating conditions.
So although failures are rare – when they do occur – they fall into specific areas amongst which your particular problem is the most common.
Even older models had failures but the Internet has increased the exposure of these more recent examples and made the change in apparent quality seem greater than it actually is.
It is not for us to comment on what Porsche regard as an acceptable failure rate set against potential profitability - but it seems they were content with the results for these engines manufactured since about 1995 as little seems to have been done to correct the weaknesses or provide affordable solutions which has fallen to the few specialists with the experience and equipment to try and fill the void – like us – despite having minute resources, smaller samples and little information about numbers and statistics (which Porsche have at their disposal through analysing their spares and replacement engine provisions).
Your cylinder does not have plating on the bore - but has a cast in composite liner that is then bored and honed (rather like more traditional cast in iron liners). Your piston has a normally reliable Teflon type coating applied (as does later 996’s, 997’s and Cayman S engines).
All these engines are developments of the original Boxster 2.5 engine – almost identical design and internals, same overall sizes (block height etc) but the capacity and change to variable valve lift has greatly increased the torque and power outputs (particularly at low revs) adding to piston to cylinder wall loading - while the shorter con rods has increased that pressure even further and the space for coolant has been reduced as cylinder diameters have increased in the same block.
Older examples provided the most cylinder/piston wall loading at higher revs – so the problem was more likely to occur for the smaller number of owners driving their cars aggressively as more sympathetic drivers changed gear at lower revs and their engines were more lightly loaded. However - because the low revs torque is so much greater – with these later engines - the load on the piston/cylinder wall is much higher - even when a driver is not revving the car high or therefore thinks he is not driving aggressively or near limits – simply enjoying good performance without realising the consequences – and so we find that a greater number of “more modest” drivers are experiencing this failure than before.
So something in this equation - with each new model - of gradually increasing the piston face load while many other facets of the design remain the same – has gradually pushed the safe operating limit nearer to that in normal use and therefore has increased the small number of failures that result.
We have identified several possible contributory factors and when we rebuild engines we address these by making appropriate changes to reduce a future repetition.
The result of a failure is the piston coating missing or delaminating - a resulting scored bore and piston seized on the thrust face – almost always on the number 2 bank (cylinders 4, 5 or 6 because the thrust face is hotter on this side and the coolant probably slightly hotter). This is usually accompanied by higher oil consumption and/or smoking results often followed by a ticking noise as the piston tilts (due to the seizure and increased clearance) and hits the cylinder head. We can bore out the scored liner and replace it and the piston to affect a repair at a much lower cost than a new engine and also make changes to improve the weaknesses that we think are contributory.
While we do so - we also offer (for very little extra cost) to alter some other unconnected parts we regard as weak areas - to make the engine more robust than it was before or than a new one.
We are also investing heavily in ways to reduce the repair costs in the future – because we believe this to be a problem that will afflict a lot of engines (although still statistically small overall).
Because the cost of this investment is relatively - very high for us – I am not prepared right now to explain or describe every cause or future development we have up our sleeves or in test – for pure commercial reasons - although cylinder wall operating temperatures and its influence on oil viscosity and the materials under load are a clue. When “your” problem occurs it is usually between about 25K and 50K. If the engine survives until a radiator leaks, a water pump fails, a cylinder head cracks or anything else occurs to cause overheating – then that may well also initiate this unfortunate failure.
In addition to this there is a purely manufacturing machining problem we have also previously identified (one that we correct during reconditioning) that can cause cylinder head gasket leakage and overheating the cylinder through reduction in cooling that could occur sooner (and has caused this very problem in a car/engine received for repair only this week after only 17K).
Please note that due to pressure of work repairing these engines - we have not been able to update the explanations or photos about these engine failures in our buyers guide for several years (www.hartech.org buyers guide section 4) so there is a lot more currently going on here than covered there.
For further information please contact Baz or Grant on 01204 302809.
Firstly – statistically these failures are very rare and therefore most examples are perfectly OK. It seems a lot to us because we receive cars and engines to repair every day of the week –with one of perhaps two or three typical problems - but taken overall – Country wide - there are relatively few.
Any engine that is driven to its limits will eventually fail one day and when it does it will always find the weakest part of the chain to fail first (or there may be a few weak links). The lighter the internals are made and/or the higher the power output or revs and/or the lower the production costs – in most cases the sooner such an engine driven to its limits will find those weak areas.
These engines have excellent outputs and light weight internals and have been manufactured by more modern (and in many areas lower cost production) methods than earlier Porsche examples – but this does not automatically make them inferior – just pushes the envelope or limits nearer to daily operating conditions.
So although failures are rare – when they do occur – they fall into specific areas amongst which your particular problem is the most common.
Even older models had failures but the Internet has increased the exposure of these more recent examples and made the change in apparent quality seem greater than it actually is.
It is not for us to comment on what Porsche regard as an acceptable failure rate set against potential profitability - but it seems they were content with the results for these engines manufactured since about 1995 as little seems to have been done to correct the weaknesses or provide affordable solutions which has fallen to the few specialists with the experience and equipment to try and fill the void – like us – despite having minute resources, smaller samples and little information about numbers and statistics (which Porsche have at their disposal through analysing their spares and replacement engine provisions).
Your cylinder does not have plating on the bore - but has a cast in composite liner that is then bored and honed (rather like more traditional cast in iron liners). Your piston has a normally reliable Teflon type coating applied (as does later 996’s, 997’s and Cayman S engines).
All these engines are developments of the original Boxster 2.5 engine – almost identical design and internals, same overall sizes (block height etc) but the capacity and change to variable valve lift has greatly increased the torque and power outputs (particularly at low revs) adding to piston to cylinder wall loading - while the shorter con rods has increased that pressure even further and the space for coolant has been reduced as cylinder diameters have increased in the same block.
Older examples provided the most cylinder/piston wall loading at higher revs – so the problem was more likely to occur for the smaller number of owners driving their cars aggressively as more sympathetic drivers changed gear at lower revs and their engines were more lightly loaded. However - because the low revs torque is so much greater – with these later engines - the load on the piston/cylinder wall is much higher - even when a driver is not revving the car high or therefore thinks he is not driving aggressively or near limits – simply enjoying good performance without realising the consequences – and so we find that a greater number of “more modest” drivers are experiencing this failure than before.
So something in this equation - with each new model - of gradually increasing the piston face load while many other facets of the design remain the same – has gradually pushed the safe operating limit nearer to that in normal use and therefore has increased the small number of failures that result.
We have identified several possible contributory factors and when we rebuild engines we address these by making appropriate changes to reduce a future repetition.
The result of a failure is the piston coating missing or delaminating - a resulting scored bore and piston seized on the thrust face – almost always on the number 2 bank (cylinders 4, 5 or 6 because the thrust face is hotter on this side and the coolant probably slightly hotter). This is usually accompanied by higher oil consumption and/or smoking results often followed by a ticking noise as the piston tilts (due to the seizure and increased clearance) and hits the cylinder head. We can bore out the scored liner and replace it and the piston to affect a repair at a much lower cost than a new engine and also make changes to improve the weaknesses that we think are contributory.
While we do so - we also offer (for very little extra cost) to alter some other unconnected parts we regard as weak areas - to make the engine more robust than it was before or than a new one.
We are also investing heavily in ways to reduce the repair costs in the future – because we believe this to be a problem that will afflict a lot of engines (although still statistically small overall).
Because the cost of this investment is relatively - very high for us – I am not prepared right now to explain or describe every cause or future development we have up our sleeves or in test – for pure commercial reasons - although cylinder wall operating temperatures and its influence on oil viscosity and the materials under load are a clue. When “your” problem occurs it is usually between about 25K and 50K. If the engine survives until a radiator leaks, a water pump fails, a cylinder head cracks or anything else occurs to cause overheating – then that may well also initiate this unfortunate failure.
In addition to this there is a purely manufacturing machining problem we have also previously identified (one that we correct during reconditioning) that can cause cylinder head gasket leakage and overheating the cylinder through reduction in cooling that could occur sooner (and has caused this very problem in a car/engine received for repair only this week after only 17K).
Please note that due to pressure of work repairing these engines - we have not been able to update the explanations or photos about these engine failures in our buyers guide for several years (www.hartech.org buyers guide section 4) so there is a lot more currently going on here than covered there.
For further information please contact Baz or Grant on 01204 302809.
There is a longstanding discussion of the reliability issues of these engines here:
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
As Baz says, these failures do happen but the tendancy of people to only post negative experiences on the internet gives the impression such failures are more common than they actually are.
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
As Baz says, these failures do happen but the tendancy of people to only post negative experiences on the internet gives the impression such failures are more common than they actually are.
Chans, Sorry to hear about your C4S.
Unfortunately I think almost the exact same thing has been picked up on my 2002 996 C4S during its standard service last month.
Noise at idle was inspected with a boroscope camera at which point they found damage to number 6 cylinder where piston has worn through bone wall.
Totally gutted was an understatement! Had put some cash a side for wear and tear work but nothing could have prepared me for this. Potential new engine/engine rebuild £££££
Made a call to Hartech following some goggling and searching on here. Have to say they where massively helpful and very knowledgeable. Must of spent well over an hour on the phone to them bending there ear in the next few days running through the options, processes, cost break downs etc etc. Fair play!
Think I have finally decided the single cylinder liner replacement and new piston option is the way I’m going to go. Hartech plus a few others as I understand offer this option. Plus some optional future proofing of key areas you can take advantage of if you like whilst they have the engine out. ( Timing Chain, Crank Bearing, IMS Bearing, and Support Rings)
Chans what did you do in the end? Has anyone else on here had the same cylinder scorching nightmare? and /or gone down the single cylinder replacement option? Keen to hear what you chaps think.
Thanks
Unfortunately I think almost the exact same thing has been picked up on my 2002 996 C4S during its standard service last month.
Noise at idle was inspected with a boroscope camera at which point they found damage to number 6 cylinder where piston has worn through bone wall.
Totally gutted was an understatement! Had put some cash a side for wear and tear work but nothing could have prepared me for this. Potential new engine/engine rebuild £££££
Made a call to Hartech following some goggling and searching on here. Have to say they where massively helpful and very knowledgeable. Must of spent well over an hour on the phone to them bending there ear in the next few days running through the options, processes, cost break downs etc etc. Fair play!
Think I have finally decided the single cylinder liner replacement and new piston option is the way I’m going to go. Hartech plus a few others as I understand offer this option. Plus some optional future proofing of key areas you can take advantage of if you like whilst they have the engine out. ( Timing Chain, Crank Bearing, IMS Bearing, and Support Rings)
Chans what did you do in the end? Has anyone else on here had the same cylinder scorching nightmare? and /or gone down the single cylinder replacement option? Keen to hear what you chaps think.
Thanks
HiG11ARR, glad you found us helpful - we try!
This problem is becoming quite common (in the mix of the usual failures) with this model (and to a lesser extent the 3.8 and Cayman S 3.4). It is the piston face that has badly scored up on one side marking the cylinder wall (but you can only see the scoring - not the piston - with a camera).
After repairing increasing numbers with new liners and pistons we have bought a 996 and fitted temperature sensors into strategic parts of the engine to test out the theory we had about temperatures inside the block being so high they can become critical in some rare circumstances and the results have substantiated our theory (full reports with graphs and technical explanations etc will follow - probably over the Christmas break when I get time to write them).
There are several ways we can help (one of which may be particularly relevant to you).
(1) For owners whose cars are still OK we are marketing a coolant change combined with fitting a lower temperature thermostat running 12 degrees C lower (71 instead of 83) which is a better temperature for power - resulting in a power increase and better for reliability as some parts of the engine run close to boiling point - because the thermostat controls the temperature going into the engine - not leaving it - more details in the technical report to follow). We think this will prevent cylinder scoring in most cases and we have tested both standard and our lower temperature thermostats and proven the benefit to cylinder wall temperatures. There is a long procedure to bleed these cars when changing coolant so it is quite expensive to change just a thermostat but if combined with say a radiator change or a water pump replacement (or an engine rebuild) - it becomes just a relatively small extra cost for a benefit in reliability.
(2) For owners like you who have suffered a failure we are (I think) the only specialists offering to replace a single cylinder and piston, modify the coolant flow to subsequently lower the cylinder wall temperatures in the future and the thermostat. We are also the only ones who can re-round the other cylinders and fit restraining rings (the gradual ovality contributing to the cause of the scoring in the first place) and so our rebuilt engines are better protected than anyone elses (to my knowledge) - especially when fitted with the low temperature thermostat that is now standard practice for all our rebuilds of 3.6, 3.8 and Cayman S engines.
(3) We have had some special oversized pistons designed and manufactured for the 3.6 and 3.8 engines (Cayman to follow) so instead of fitting a new liner we can in future re-bore the cylinder and fit a slightly larger piston - so reducing costs (although restraining rings will still need to be fitted so as we have our own "IN-HOUSE" precision machine shop in which we manufacture and modify all these components - we will not be just supplying pistons - only rebuilding bottom ends as a minimum rebuild as the job requires more than just fitting new pistons to do it properly).
However the logistics of finding suitable cars - carrying out the mods and then putting enough miles on them to prove the results - is a major headache that could delay testing for months before others can benefit from the outcome. We have already bought cars to test out not only the temperature situation - but also some other developments that will be offered in the future - like re-hardened and re-ground crankshafts fitted with our own wider shells (currently under test in yet another car we have bought and modified) and all Ok so far), re-machined oil pump housings fitted with different oil pump gears (tests complete in another car and all OK), to add to the already tested and proven IMS bearing and shaft replacements, re-rounding - restraining sleeves, liners, etc that form part of our TOTAL ENGINE REBUILD PACKAGE. We have also successfully tested re-welded (previously cracked) cylinder heads and re-line bored camshaft housings – but it all takes time to get from the starting point to offering it as a commercial solution.
It will help us speed up piston testing if we were able to use a customer rebuild (for which purpose we would offer a financial benefit and obviously guarantee the resulting engine costs if for any reason there was a technical problem that required further work). This is the possible relevant position we could offer to you as the pistons are currently in transit to us.
We obviously prefer to keep all testing in house but no customers with damaged engines in the newer more expensive models have wanted to sell their cars and we cannot justify buying perfectly good cars (at newer prices) and stripping and rebuilding them to test out modifications and new components when even the testing time alone would restrict us (let alone the costs with so many models affected).
So far every technical explanation, shortcoming in existing designs, modified or re-manufactured parts or newly designed and manufactured parts - we have made for this whole range of engines has proven perfectly OK, reliable and correct and everything we have written about the subject has proven accurate and right - so we have an excellent record for identifying problems and finding viable solutions.
Although I notice that others are now trying to jump on the band-wagon offering engine rebuilds - I do not think there is anyone else to match the experience, in house facilities, technical solutions, new products, nor success and with a stores full of used, manufactured and modified parts for all models (from the original 2.5 Boxster right up to the Cayman S) – providing rebuilt bottom ends and heads etc - I don't think anyone else matches the investment or effort we have put into helping owners experiencing these problems.
Although it is a bit of good fortune that I happened to have the right background to manage such issues - the sheer numbers of problems and range of models they affect - the time and investment needed in equipment, products, staffing and facilities and the training and supervision necessary - leave little time to then write technical explanations and provide photos etc to justify to the public what we do and why we are streets ahead of any opposition. Indeed the very depth of involvement we have put into it actually handicaps our time compared to others simply offering to rebuild an engine (usually without any of the modifications and special parts we have proven to work and be necessary) which is a source of some irritation.
I have no problem with any competitor providing a reliable service - nor with individuals choosing who to go to for themselves - (and we happily rebuild bottom ends and whole engines for many well respected specialists) but I do have a problem with our provision being considered in the same frame as others - because if only I had the time available to explain and demonstrate what we are doing up here in Bolton and why (for very competitive prices) - I think they would have to up their game considerably to even remotely compete.
We have a machine shop with three mills, two lathes, and a cylinder head machining centre, two rebuild rooms, enough parts to build about 20 engines, are involved in the Boxster race series (for which we manufactured a reliable directional valved sump extension due to be offered for sale next year), have built a successful 3 litre 944 turbo (report in 911 and Porsche world - currently mark two in build designed for over 500 bhp), are sponsoring a driver in the Porsche Championship next season and already have a good reputation for re-manufacturing a wide range of suspension components. We were the first to offer a monthly paid Lifetime Maintenance Packeage and are probably the leading service centre in the North West.
By doing so much - what we don’t (unfortunately) also have is enough time to promote all that as well as many others do - with less on their plate.
On top of all that (as G11ARR found) we make time to discuss things with the many customers that do come our way.
It is a great shame that so many owners first take their car to a local specialist to investigate only to end up with the car here after paying them for that investigative work that we may have found unnecessary – then for the car and stripped parts to be transported to Bolton (when in some cases they could have driven it) - so if you have problems (or suspect you have) it will save you money to include us in the list of people you talk to before doing anything else (and then ask elsewhere if they offer what you will discover we do).
Although it is several years out of date now – a lot of info is on our web site buyers guide section 4 (with photos) www.hartech.org and I am currently trying to update it and include recent developments applying to newer models.
Finally - provision of a service CENTRE nearer London (to investigate problems and remove and re-fit engines) is currently being considered.
Baz
This problem is becoming quite common (in the mix of the usual failures) with this model (and to a lesser extent the 3.8 and Cayman S 3.4). It is the piston face that has badly scored up on one side marking the cylinder wall (but you can only see the scoring - not the piston - with a camera).
After repairing increasing numbers with new liners and pistons we have bought a 996 and fitted temperature sensors into strategic parts of the engine to test out the theory we had about temperatures inside the block being so high they can become critical in some rare circumstances and the results have substantiated our theory (full reports with graphs and technical explanations etc will follow - probably over the Christmas break when I get time to write them).
There are several ways we can help (one of which may be particularly relevant to you).
(1) For owners whose cars are still OK we are marketing a coolant change combined with fitting a lower temperature thermostat running 12 degrees C lower (71 instead of 83) which is a better temperature for power - resulting in a power increase and better for reliability as some parts of the engine run close to boiling point - because the thermostat controls the temperature going into the engine - not leaving it - more details in the technical report to follow). We think this will prevent cylinder scoring in most cases and we have tested both standard and our lower temperature thermostats and proven the benefit to cylinder wall temperatures. There is a long procedure to bleed these cars when changing coolant so it is quite expensive to change just a thermostat but if combined with say a radiator change or a water pump replacement (or an engine rebuild) - it becomes just a relatively small extra cost for a benefit in reliability.
(2) For owners like you who have suffered a failure we are (I think) the only specialists offering to replace a single cylinder and piston, modify the coolant flow to subsequently lower the cylinder wall temperatures in the future and the thermostat. We are also the only ones who can re-round the other cylinders and fit restraining rings (the gradual ovality contributing to the cause of the scoring in the first place) and so our rebuilt engines are better protected than anyone elses (to my knowledge) - especially when fitted with the low temperature thermostat that is now standard practice for all our rebuilds of 3.6, 3.8 and Cayman S engines.
(3) We have had some special oversized pistons designed and manufactured for the 3.6 and 3.8 engines (Cayman to follow) so instead of fitting a new liner we can in future re-bore the cylinder and fit a slightly larger piston - so reducing costs (although restraining rings will still need to be fitted so as we have our own "IN-HOUSE" precision machine shop in which we manufacture and modify all these components - we will not be just supplying pistons - only rebuilding bottom ends as a minimum rebuild as the job requires more than just fitting new pistons to do it properly).
However the logistics of finding suitable cars - carrying out the mods and then putting enough miles on them to prove the results - is a major headache that could delay testing for months before others can benefit from the outcome. We have already bought cars to test out not only the temperature situation - but also some other developments that will be offered in the future - like re-hardened and re-ground crankshafts fitted with our own wider shells (currently under test in yet another car we have bought and modified) and all Ok so far), re-machined oil pump housings fitted with different oil pump gears (tests complete in another car and all OK), to add to the already tested and proven IMS bearing and shaft replacements, re-rounding - restraining sleeves, liners, etc that form part of our TOTAL ENGINE REBUILD PACKAGE. We have also successfully tested re-welded (previously cracked) cylinder heads and re-line bored camshaft housings – but it all takes time to get from the starting point to offering it as a commercial solution.
It will help us speed up piston testing if we were able to use a customer rebuild (for which purpose we would offer a financial benefit and obviously guarantee the resulting engine costs if for any reason there was a technical problem that required further work). This is the possible relevant position we could offer to you as the pistons are currently in transit to us.
We obviously prefer to keep all testing in house but no customers with damaged engines in the newer more expensive models have wanted to sell their cars and we cannot justify buying perfectly good cars (at newer prices) and stripping and rebuilding them to test out modifications and new components when even the testing time alone would restrict us (let alone the costs with so many models affected).
So far every technical explanation, shortcoming in existing designs, modified or re-manufactured parts or newly designed and manufactured parts - we have made for this whole range of engines has proven perfectly OK, reliable and correct and everything we have written about the subject has proven accurate and right - so we have an excellent record for identifying problems and finding viable solutions.
Although I notice that others are now trying to jump on the band-wagon offering engine rebuilds - I do not think there is anyone else to match the experience, in house facilities, technical solutions, new products, nor success and with a stores full of used, manufactured and modified parts for all models (from the original 2.5 Boxster right up to the Cayman S) – providing rebuilt bottom ends and heads etc - I don't think anyone else matches the investment or effort we have put into helping owners experiencing these problems.
Although it is a bit of good fortune that I happened to have the right background to manage such issues - the sheer numbers of problems and range of models they affect - the time and investment needed in equipment, products, staffing and facilities and the training and supervision necessary - leave little time to then write technical explanations and provide photos etc to justify to the public what we do and why we are streets ahead of any opposition. Indeed the very depth of involvement we have put into it actually handicaps our time compared to others simply offering to rebuild an engine (usually without any of the modifications and special parts we have proven to work and be necessary) which is a source of some irritation.
I have no problem with any competitor providing a reliable service - nor with individuals choosing who to go to for themselves - (and we happily rebuild bottom ends and whole engines for many well respected specialists) but I do have a problem with our provision being considered in the same frame as others - because if only I had the time available to explain and demonstrate what we are doing up here in Bolton and why (for very competitive prices) - I think they would have to up their game considerably to even remotely compete.
We have a machine shop with three mills, two lathes, and a cylinder head machining centre, two rebuild rooms, enough parts to build about 20 engines, are involved in the Boxster race series (for which we manufactured a reliable directional valved sump extension due to be offered for sale next year), have built a successful 3 litre 944 turbo (report in 911 and Porsche world - currently mark two in build designed for over 500 bhp), are sponsoring a driver in the Porsche Championship next season and already have a good reputation for re-manufacturing a wide range of suspension components. We were the first to offer a monthly paid Lifetime Maintenance Packeage and are probably the leading service centre in the North West.
By doing so much - what we don’t (unfortunately) also have is enough time to promote all that as well as many others do - with less on their plate.
On top of all that (as G11ARR found) we make time to discuss things with the many customers that do come our way.
It is a great shame that so many owners first take their car to a local specialist to investigate only to end up with the car here after paying them for that investigative work that we may have found unnecessary – then for the car and stripped parts to be transported to Bolton (when in some cases they could have driven it) - so if you have problems (or suspect you have) it will save you money to include us in the list of people you talk to before doing anything else (and then ask elsewhere if they offer what you will discover we do).
Although it is several years out of date now – a lot of info is on our web site buyers guide section 4 (with photos) www.hartech.org and I am currently trying to update it and include recent developments applying to newer models.
Finally - provision of a service CENTRE nearer London (to investigate problems and remove and re-fit engines) is currently being considered.
Baz
hartech said:
HiG11ARR, glad you found us helpful - we try!
This problem is becoming quite common (in the mix of the usual failures) with this model (and to a lesser extent the 3.8 and Cayman S 3.4). It is the piston face that has badly scored up on one side marking the cylinder wall (but you can only see the scoring - not the piston - with a camera).
After repairing increasing numbers with new liners and pistons we have bought a 996 and fitted temperature sensors into strategic parts of the engine to test out the theory we had about temperatures inside the block being so high they can become critical in some rare circumstances and the results have substantiated our theory (full reports with graphs and technical explanations etc will follow - probably over the Christmas break when I get time to write them).
There are several ways we can help (one of which may be particularly relevant to you).
(1) For owners whose cars are still OK we are marketing a coolant change combined with fitting a lower temperature thermostat running 12 degrees C lower (71 instead of 83) which is a better temperature for power - resulting in a power increase and better for reliability as some parts of the engine run close to boiling point - because the thermostat controls the temperature going into the engine - not leaving it - more details in the technical report to follow). We think this will prevent cylinder scoring in most cases and we have tested both standard and our lower temperature thermostats and proven the benefit to cylinder wall temperatures. There is a long procedure to bleed these cars when changing coolant so it is quite expensive to change just a thermostat but if combined with say a radiator change or a water pump replacement (or an engine rebuild) - it becomes just a relatively small extra cost for a benefit in reliability.
(2) For owners like you who have suffered a failure we are (I think) the only specialists offering to replace a single cylinder and piston, modify the coolant flow to subsequently lower the cylinder wall temperatures in the future and the thermostat. We are also the only ones who can re-round the other cylinders and fit restraining rings (the gradual ovality contributing to the cause of the scoring in the first place) and so our rebuilt engines are better protected than anyone elses (to my knowledge) - especially when fitted with the low temperature thermostat that is now standard practice for all our rebuilds of 3.6, 3.8 and Cayman S engines.
(3) We have had some special oversized pistons designed and manufactured for the 3.6 and 3.8 engines (Cayman to follow) so instead of fitting a new liner we can in future re-bore the cylinder and fit a slightly larger piston - so reducing costs (although restraining rings will still need to be fitted so as we have our own "IN-HOUSE" precision machine shop in which we manufacture and modify all these components - we will not be just supplying pistons - only rebuilding bottom ends as a minimum rebuild as the job requires more than just fitting new pistons to do it properly).
However the logistics of finding suitable cars - carrying out the mods and then putting enough miles on them to prove the results - is a major headache that could delay testing for months before others can benefit from the outcome. We have already bought cars to test out not only the temperature situation - but also some other developments that will be offered in the future - like re-hardened and re-ground crankshafts fitted with our own wider shells (currently under test in yet another car we have bought and modified) and all Ok so far), re-machined oil pump housings fitted with different oil pump gears (tests complete in another car and all OK), to add to the already tested and proven IMS bearing and shaft replacements, re-rounding - restraining sleeves, liners, etc that form part of our TOTAL ENGINE REBUILD PACKAGE. We have also successfully tested re-welded (previously cracked) cylinder heads and re-line bored camshaft housings – but it all takes time to get from the starting point to offering it as a commercial solution.
It will help us speed up piston testing if we were able to use a customer rebuild (for which purpose we would offer a financial benefit and obviously guarantee the resulting engine costs if for any reason there was a technical problem that required further work). This is the possible relevant position we could offer to you as the pistons are currently in transit to us.
We obviously prefer to keep all testing in house but no customers with damaged engines in the newer more expensive models have wanted to sell their cars and we cannot justify buying perfectly good cars (at newer prices) and stripping and rebuilding them to test out modifications and new components when even the testing time alone would restrict us (let alone the costs with so many models affected).
So far every technical explanation, shortcoming in existing designs, modified or re-manufactured parts or newly designed and manufactured parts - we have made for this whole range of engines has proven perfectly OK, reliable and correct and everything we have written about the subject has proven accurate and right - so we have an excellent record for identifying problems and finding viable solutions.
Although I notice that others are now trying to jump on the band-wagon offering engine rebuilds - I do not think there is anyone else to match the experience, in house facilities, technical solutions, new products, nor success and with a stores full of used, manufactured and modified parts for all models (from the original 2.5 Boxster right up to the Cayman S) – providing rebuilt bottom ends and heads etc - I don't think anyone else matches the investment or effort we have put into helping owners experiencing these problems.
Although it is a bit of good fortune that I happened to have the right background to manage such issues - the sheer numbers of problems and range of models they affect - the time and investment needed in equipment, products, staffing and facilities and the training and supervision necessary - leave little time to then write technical explanations and provide photos etc to justify to the public what we do and why we are streets ahead of any opposition. Indeed the very depth of involvement we have put into it actually handicaps our time compared to others simply offering to rebuild an engine (usually without any of the modifications and special parts we have proven to work and be necessary) which is a source of some irritation.
I have no problem with any competitor providing a reliable service - nor with individuals choosing who to go to for themselves - (and we happily rebuild bottom ends and whole engines for many well respected specialists) but I do have a problem with our provision being considered in the same frame as others - because if only I had the time available to explain and demonstrate what we are doing up here in Bolton and why (for very competitive prices) - I think they would have to up their game considerably to even remotely compete.
We have a machine shop with three mills, two lathes, and a cylinder head machining centre, two rebuild rooms, enough parts to build about 20 engines, are involved in the Boxster race series (for which we manufactured a reliable directional valved sump extension due to be offered for sale next year), have built a successful 3 litre 944 turbo (report in 911 and Porsche world - currently mark two in build designed for over 500 bhp), are sponsoring a driver in the Porsche Championship next season and already have a good reputation for re-manufacturing a wide range of suspension components. We were the first to offer a monthly paid Lifetime Maintenance Packeage and are probably the leading service centre in the North West.
By doing so much - what we don’t (unfortunately) also have is enough time to promote all that as well as many others do - with less on their plate.
On top of all that (as G11ARR found) we make time to discuss things with the many customers that do come our way.
It is a great shame that so many owners first take their car to a local specialist to investigate only to end up with the car here after paying them for that investigative work that we may have found unnecessary – then for the car and stripped parts to be transported to Bolton (when in some cases they could have driven it) - so if you have problems (or suspect you have) it will save you money to include us in the list of people you talk to before doing anything else (and then ask elsewhere if they offer what you will discover we do).
Although it is several years out of date now – a lot of info is on our web site buyers guide section 4 (with photos) www.hartech.org and I am currently trying to update it and include recent developments applying to newer models.
Finally - provision of a service CENTRE nearer London (to investigate problems and remove and re-fit engines) is currently being considered.
Baz
Hi Baz,This problem is becoming quite common (in the mix of the usual failures) with this model (and to a lesser extent the 3.8 and Cayman S 3.4). It is the piston face that has badly scored up on one side marking the cylinder wall (but you can only see the scoring - not the piston - with a camera).
After repairing increasing numbers with new liners and pistons we have bought a 996 and fitted temperature sensors into strategic parts of the engine to test out the theory we had about temperatures inside the block being so high they can become critical in some rare circumstances and the results have substantiated our theory (full reports with graphs and technical explanations etc will follow - probably over the Christmas break when I get time to write them).
There are several ways we can help (one of which may be particularly relevant to you).
(1) For owners whose cars are still OK we are marketing a coolant change combined with fitting a lower temperature thermostat running 12 degrees C lower (71 instead of 83) which is a better temperature for power - resulting in a power increase and better for reliability as some parts of the engine run close to boiling point - because the thermostat controls the temperature going into the engine - not leaving it - more details in the technical report to follow). We think this will prevent cylinder scoring in most cases and we have tested both standard and our lower temperature thermostats and proven the benefit to cylinder wall temperatures. There is a long procedure to bleed these cars when changing coolant so it is quite expensive to change just a thermostat but if combined with say a radiator change or a water pump replacement (or an engine rebuild) - it becomes just a relatively small extra cost for a benefit in reliability.
(2) For owners like you who have suffered a failure we are (I think) the only specialists offering to replace a single cylinder and piston, modify the coolant flow to subsequently lower the cylinder wall temperatures in the future and the thermostat. We are also the only ones who can re-round the other cylinders and fit restraining rings (the gradual ovality contributing to the cause of the scoring in the first place) and so our rebuilt engines are better protected than anyone elses (to my knowledge) - especially when fitted with the low temperature thermostat that is now standard practice for all our rebuilds of 3.6, 3.8 and Cayman S engines.
(3) We have had some special oversized pistons designed and manufactured for the 3.6 and 3.8 engines (Cayman to follow) so instead of fitting a new liner we can in future re-bore the cylinder and fit a slightly larger piston - so reducing costs (although restraining rings will still need to be fitted so as we have our own "IN-HOUSE" precision machine shop in which we manufacture and modify all these components - we will not be just supplying pistons - only rebuilding bottom ends as a minimum rebuild as the job requires more than just fitting new pistons to do it properly).
However the logistics of finding suitable cars - carrying out the mods and then putting enough miles on them to prove the results - is a major headache that could delay testing for months before others can benefit from the outcome. We have already bought cars to test out not only the temperature situation - but also some other developments that will be offered in the future - like re-hardened and re-ground crankshafts fitted with our own wider shells (currently under test in yet another car we have bought and modified) and all Ok so far), re-machined oil pump housings fitted with different oil pump gears (tests complete in another car and all OK), to add to the already tested and proven IMS bearing and shaft replacements, re-rounding - restraining sleeves, liners, etc that form part of our TOTAL ENGINE REBUILD PACKAGE. We have also successfully tested re-welded (previously cracked) cylinder heads and re-line bored camshaft housings – but it all takes time to get from the starting point to offering it as a commercial solution.
It will help us speed up piston testing if we were able to use a customer rebuild (for which purpose we would offer a financial benefit and obviously guarantee the resulting engine costs if for any reason there was a technical problem that required further work). This is the possible relevant position we could offer to you as the pistons are currently in transit to us.
We obviously prefer to keep all testing in house but no customers with damaged engines in the newer more expensive models have wanted to sell their cars and we cannot justify buying perfectly good cars (at newer prices) and stripping and rebuilding them to test out modifications and new components when even the testing time alone would restrict us (let alone the costs with so many models affected).
So far every technical explanation, shortcoming in existing designs, modified or re-manufactured parts or newly designed and manufactured parts - we have made for this whole range of engines has proven perfectly OK, reliable and correct and everything we have written about the subject has proven accurate and right - so we have an excellent record for identifying problems and finding viable solutions.
Although I notice that others are now trying to jump on the band-wagon offering engine rebuilds - I do not think there is anyone else to match the experience, in house facilities, technical solutions, new products, nor success and with a stores full of used, manufactured and modified parts for all models (from the original 2.5 Boxster right up to the Cayman S) – providing rebuilt bottom ends and heads etc - I don't think anyone else matches the investment or effort we have put into helping owners experiencing these problems.
Although it is a bit of good fortune that I happened to have the right background to manage such issues - the sheer numbers of problems and range of models they affect - the time and investment needed in equipment, products, staffing and facilities and the training and supervision necessary - leave little time to then write technical explanations and provide photos etc to justify to the public what we do and why we are streets ahead of any opposition. Indeed the very depth of involvement we have put into it actually handicaps our time compared to others simply offering to rebuild an engine (usually without any of the modifications and special parts we have proven to work and be necessary) which is a source of some irritation.
I have no problem with any competitor providing a reliable service - nor with individuals choosing who to go to for themselves - (and we happily rebuild bottom ends and whole engines for many well respected specialists) but I do have a problem with our provision being considered in the same frame as others - because if only I had the time available to explain and demonstrate what we are doing up here in Bolton and why (for very competitive prices) - I think they would have to up their game considerably to even remotely compete.
We have a machine shop with three mills, two lathes, and a cylinder head machining centre, two rebuild rooms, enough parts to build about 20 engines, are involved in the Boxster race series (for which we manufactured a reliable directional valved sump extension due to be offered for sale next year), have built a successful 3 litre 944 turbo (report in 911 and Porsche world - currently mark two in build designed for over 500 bhp), are sponsoring a driver in the Porsche Championship next season and already have a good reputation for re-manufacturing a wide range of suspension components. We were the first to offer a monthly paid Lifetime Maintenance Packeage and are probably the leading service centre in the North West.
By doing so much - what we don’t (unfortunately) also have is enough time to promote all that as well as many others do - with less on their plate.
On top of all that (as G11ARR found) we make time to discuss things with the many customers that do come our way.
It is a great shame that so many owners first take their car to a local specialist to investigate only to end up with the car here after paying them for that investigative work that we may have found unnecessary – then for the car and stripped parts to be transported to Bolton (when in some cases they could have driven it) - so if you have problems (or suspect you have) it will save you money to include us in the list of people you talk to before doing anything else (and then ask elsewhere if they offer what you will discover we do).
Although it is several years out of date now – a lot of info is on our web site buyers guide section 4 (with photos) www.hartech.org and I am currently trying to update it and include recent developments applying to newer models.
Finally - provision of a service CENTRE nearer London (to investigate problems and remove and re-fit engines) is currently being considered.
Baz
I have read with interest your technical explanations of the various reasons for engine failures in N/A 996's & 997's. Being the owner of a 996 turbo, I know the engine is completely different from the N/A's, but I wondered if you had ever come across any weaknesses in the 996t engines and do you have any recommended mods. for this engine.
Many thanks from all Porsche owners.
Hi Carcrazy pop, thank you for your kind comments.
We do not see as many turbos as std cars and the engines are much better (and much more expensive). Whereas Porsche used to make engines for std 944's and 911's with much the same parts in the std and turbo engines (meaning the std versions were much too over engineered) and correspondingly made no money out of it - they have now designed for pupose and made some money doing so.
It's a shame really because many ideas that feature in the M96 and M97 engines are better than some of those in the older engines (balanced and equalised coolant delivery, steel inserts in crankshaft bearing carriers, Lokasil liner material etc) inevitably when trying to make such a powerful and ecconomical emmision controlled engine - with water cooling - a few design areas could have been done a little better (IMS bearing design, weak free standing cylinders, running the coolant too hot in some cases).
My own 996 has covered 150K still on mainly original parts - so they were well designed in most areas - just a little lacking in others that needed analysing and fixing - after which they can go on and on again (and many will never fail anyway - only the few).
The turbo engine is based on the original 993 crankcases and crankshaft etc and features cylinder liners - very similar to the ones we fit to the cheaper engines to repair them.
The only issue (apart from exhaust corrosion and clutch helpers) seems to be that the intermediate gears were cut a little slacker (with more backlash) and can rattle a bit at low revs when they have worn a bit. The original design used one alloy gear and perhaps this damped it out!
They are great cars considering the performance - take care.
Baz
We do not see as many turbos as std cars and the engines are much better (and much more expensive). Whereas Porsche used to make engines for std 944's and 911's with much the same parts in the std and turbo engines (meaning the std versions were much too over engineered) and correspondingly made no money out of it - they have now designed for pupose and made some money doing so.
It's a shame really because many ideas that feature in the M96 and M97 engines are better than some of those in the older engines (balanced and equalised coolant delivery, steel inserts in crankshaft bearing carriers, Lokasil liner material etc) inevitably when trying to make such a powerful and ecconomical emmision controlled engine - with water cooling - a few design areas could have been done a little better (IMS bearing design, weak free standing cylinders, running the coolant too hot in some cases).
My own 996 has covered 150K still on mainly original parts - so they were well designed in most areas - just a little lacking in others that needed analysing and fixing - after which they can go on and on again (and many will never fail anyway - only the few).
The turbo engine is based on the original 993 crankcases and crankshaft etc and features cylinder liners - very similar to the ones we fit to the cheaper engines to repair them.
The only issue (apart from exhaust corrosion and clutch helpers) seems to be that the intermediate gears were cut a little slacker (with more backlash) and can rattle a bit at low revs when they have worn a bit. The original design used one alloy gear and perhaps this damped it out!
They are great cars considering the performance - take care.
Baz
hartech said:
Hi Carcrazy pop, thank you for your kind comments.
We do not see as many turbos as std cars and the engines are much better (and much more expensive). Whereas Porsche used to make engines for std 944's and 911's with much the same parts in the std and turbo engines (meaning the std versions were much too over engineered) and correspondingly made no money out of it - they have now designed for pupose and made some money doing so.
It's a shame really because many ideas that feature in the M96 and M97 engines are better than some of those in the older engines (balanced and equalised coolant delivery, steel inserts in crankshaft bearing carriers, Lokasil liner material etc) inevitably when trying to make such a powerful and ecconomical emmision controlled engine - with water cooling - a few design areas could have been done a little better (IMS bearing design, weak free standing cylinders, running the coolant too hot in some cases).
My own 996 has covered 150K still on mainly original parts - so they were well designed in most areas - just a little lacking in others that needed analysing and fixing - after which they can go on and on again (and many will never fail anyway - only the few).
The turbo engine is based on the original 993 crankcases and crankshaft etc and features cylinder liners - very similar to the ones we fit to the cheaper engines to repair them.
The only issue (apart from exhaust corrosion and clutch helpers) seems to be that the intermediate gears were cut a little slacker (with more backlash) and can rattle a bit at low revs when they have worn a bit. The original design used one alloy gear and perhaps this damped it out!
They are great cars considering the performance - take care.
Baz
Baz,We do not see as many turbos as std cars and the engines are much better (and much more expensive). Whereas Porsche used to make engines for std 944's and 911's with much the same parts in the std and turbo engines (meaning the std versions were much too over engineered) and correspondingly made no money out of it - they have now designed for pupose and made some money doing so.
It's a shame really because many ideas that feature in the M96 and M97 engines are better than some of those in the older engines (balanced and equalised coolant delivery, steel inserts in crankshaft bearing carriers, Lokasil liner material etc) inevitably when trying to make such a powerful and ecconomical emmision controlled engine - with water cooling - a few design areas could have been done a little better (IMS bearing design, weak free standing cylinders, running the coolant too hot in some cases).
My own 996 has covered 150K still on mainly original parts - so they were well designed in most areas - just a little lacking in others that needed analysing and fixing - after which they can go on and on again (and many will never fail anyway - only the few).
The turbo engine is based on the original 993 crankcases and crankshaft etc and features cylinder liners - very similar to the ones we fit to the cheaper engines to repair them.
The only issue (apart from exhaust corrosion and clutch helpers) seems to be that the intermediate gears were cut a little slacker (with more backlash) and can rattle a bit at low revs when they have worn a bit. The original design used one alloy gear and perhaps this damped it out!
They are great cars considering the performance - take care.
Baz
Thanks for that and I find it quite assuring and believe I made the correct choice when getting out of my 997s and back into my 996t, a brilliant car and incredible value for money considering its performance.
Keep up the good work.
Hi Baz,
Great posts as usual - also saw some of your comments in the EVO buying guide for a Porsche Boxster btw - you're becoming famous!
Sorry for what is no doubt an obtuse question - I'm not overly mechanically minded, so here it goes (pls be gentle!):
If you're using a thermostat that is operating at a lower temp threshold, does that affect the overall operating temp of the engine (which I guess is the intention as you cannot pinpoint it to the problem cylinder?) ?
If so, how does that impact on the oil temp? Is there a risk of the oil temp reducing and hence any benefits of a cooler cylinder could be slightly negated by reduce oil temp (hence efficiency?) overall.
Hope that makes sense.
Thanks
Great posts as usual - also saw some of your comments in the EVO buying guide for a Porsche Boxster btw - you're becoming famous!
Sorry for what is no doubt an obtuse question - I'm not overly mechanically minded, so here it goes (pls be gentle!):
If you're using a thermostat that is operating at a lower temp threshold, does that affect the overall operating temp of the engine (which I guess is the intention as you cannot pinpoint it to the problem cylinder?) ?
If so, how does that impact on the oil temp? Is there a risk of the oil temp reducing and hence any benefits of a cooler cylinder could be slightly negated by reduce oil temp (hence efficiency?) overall.
Hope that makes sense.
Thanks
Actually Steve you are right that anything tat reduces coolant temperature also reduces oil temperature - so it will run at a better slightly lower oil temperature that will improve both reliability and power but slightly increase fuel consunption and emmisions - you take your choice on that. Remember that most engines ever made ran at the lower temperatures our new thermostat provides for - it is only very recently designed engines and worres about emmisions that have resulted in the higher running temperatures being applied (with the resulting reduction in reliability).
Lots more explanations and basic thermodynamics coming soon to explain this phenomenon in more detail and test results etc - it would help to be patient and await that please as writing this is using the same time I was preparing that report.
Baz
Lots more explanations and basic thermodynamics coming soon to explain this phenomenon in more detail and test results etc - it would help to be patient and await that please as writing this is using the same time I was preparing that report.
Baz
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