996-997 wet-sump engine reliability: enter your stats here!
Discussion
Re engine cooling: here are some more thoughts/ideas on the poor airflow issue through the front rads on my 996 that I mentioned earlier on. To remind you:
In the summer, say at ambient temperatures at or above 20c, when I drive slowly around my home town at say 30-40 mph (aircon off) my 996 temp guage creeps very quickly upwards to the point that the fans cut in. Otherwise and at cooler ambient temperatures, this doesnt really happen and the guage stays at its usual straight-up vertical position. My car is a standard C2 996 without the centre radiator. I have not being happy about this and have long suspected that there is a 'design inefficiency' here (am being diplomatic this time) in that because the cooling air exit port (triangular space under the front bumper) is so close to the high air pressure area under the front bumper, there is poor/low airflow through the front radiators under some conditions.
I know that the 996 Cabrio & 996 Targa have different arrangements for cooling air exit -modified front wheel arch liner. All 997 models have slatted/vented front wheelarch liners.
I have just returned from my local Porsche garage where I discovered some more very interesting aspects to this:
-the new Carrera GTS, Cayman S, 997 Targa, GT3 Gen 2 all have vastly improved air scoops in the bumper as part of the cool air intake to the radiators, ie greater frontal area.
-on all new 997 variants but not the earlier used cars I saw, the lower cooling air exit port (triangular space under the front bumper) is fully sealed up so the entire airflow exit for the front rads is through the slatted front wheel arch liners, where I would assume, safely I think that the air pressure is lower and thus the airflow through the rads would be higher. I am pretty convinced now that I have seen evidence that Porsche have responded, perhaps late, to one aspect of 911 engine cooling issues.
-the gen 2 GT3 does not have slatted front wheel arch liners but instead there is a slot, perhaps 300mm by 100mm in the wheel arch liner just above the swept-up air guide channel (which directs air into the brake disk area). I think the slot probably benefits also from a venturi effect to further lower the pressure behind the rads -a design feature you would expect to be on the GT3. I saw also that the GT3 has a different air funnel attached to the rear of the radiator which mates with the slot in the wheel arch.
I have decided pretty much now to mod my 996 and try as far a possible to replicate the GT3 arrangements. Will take photos & let you know.
In the summer, say at ambient temperatures at or above 20c, when I drive slowly around my home town at say 30-40 mph (aircon off) my 996 temp guage creeps very quickly upwards to the point that the fans cut in. Otherwise and at cooler ambient temperatures, this doesnt really happen and the guage stays at its usual straight-up vertical position. My car is a standard C2 996 without the centre radiator. I have not being happy about this and have long suspected that there is a 'design inefficiency' here (am being diplomatic this time) in that because the cooling air exit port (triangular space under the front bumper) is so close to the high air pressure area under the front bumper, there is poor/low airflow through the front radiators under some conditions.
I know that the 996 Cabrio & 996 Targa have different arrangements for cooling air exit -modified front wheel arch liner. All 997 models have slatted/vented front wheelarch liners.
I have just returned from my local Porsche garage where I discovered some more very interesting aspects to this:
-the new Carrera GTS, Cayman S, 997 Targa, GT3 Gen 2 all have vastly improved air scoops in the bumper as part of the cool air intake to the radiators, ie greater frontal area.
-on all new 997 variants but not the earlier used cars I saw, the lower cooling air exit port (triangular space under the front bumper) is fully sealed up so the entire airflow exit for the front rads is through the slatted front wheel arch liners, where I would assume, safely I think that the air pressure is lower and thus the airflow through the rads would be higher. I am pretty convinced now that I have seen evidence that Porsche have responded, perhaps late, to one aspect of 911 engine cooling issues.
-the gen 2 GT3 does not have slatted front wheel arch liners but instead there is a slot, perhaps 300mm by 100mm in the wheel arch liner just above the swept-up air guide channel (which directs air into the brake disk area). I think the slot probably benefits also from a venturi effect to further lower the pressure behind the rads -a design feature you would expect to be on the GT3. I saw also that the GT3 has a different air funnel attached to the rear of the radiator which mates with the slot in the wheel arch.
I have decided pretty much now to mod my 996 and try as far a possible to replicate the GT3 arrangements. Will take photos & let you know.
Hi Baz could it be the liners are thicker on the smaller capacity engine hence making them less prone to failure? Also in your opi nion is the scoring of the bores wear and tear or pickup caused by overheating?
Could you in a nutshell please give me your opinion of the working limits of this engine?
IE how near to its working reliable limit is it? and is this changed by the lower output and capacity,thanks in advance Baz
G
Could you in a nutshell please give me your opinion of the working limits of this engine?
IE how near to its working reliable limit is it? and is this changed by the lower output and capacity,thanks in advance Baz
G
Reply delayed - been tack testing.
If you read the buyers guide section 4 (www.hartech.org) you will find that the earlier cars had thicker liners up until the 3.4 (which was the 3.2 block bored out an extra 3mm so 1.5mm thinner wall thickenss (made worse by the fact that half is LOKASIL which is less strong and thermally unstable compared to aluminium).
The 3.4's therefore migrate oval more and sooner and eventually crack. The 3.6's and 3.8's are similar to the 3.4 (despite the extra loads) and run hotter - because more coolant is diverted through the heads and less through the cylinders(and we have just had the first 3.8 with a cracked bore - so it gets you one way or the other). The 3.8 has less space for the coolant (although this in itself may not be a bad thing).
On the other hand Lokasil (if only it was stabilised) is a superb material. it doesn't wear - just distorts if not restrained. My own 155K 996 tiptronic came in with a cracked liner @ 153K was rebuilt with original rings and pistons with 5 bores re-rounded and one liner and changed to a closed deck.
It has been smelling a little bit oily but then I only use it for 4 miles to work and back and the exhausts were full of oil (from the craked liner and oval bores) but after this trip that has stopped. I have just driven it to Brands Hatch and back (540 miles round trip including the M25 round London twice) and it returned 27.4mpg (driving as fast as the law lets you get away with and in the daytime and twice in the rush hour round London) and used hardly any oil - but it does have the lower temperature thermostat (ran @ 79 the whole time).
The problem with other solutions (like bigger or faster pumps or more air through the radiators etc) is that the thermostat restricts the flow until it reaches the set temperature and if this is high - all that will do is slow down the flow more.
Even when I was stopped on the M25 the temperature only went up to 83 (don't forget this is not what you see on the dash board but from the Air con setting digital and accurate reading) whereas with the old thermostat it would be nearer 95 to 100 (but showing far less on the dashboard).
Also please remember that if most of the coolant is going through the heads then the coolant going through the block is less and going much slower and picking up more temperature rise - but when this mixes back with the coolant from the head it minimises the result as it goes back to the thermostat (ref section 5 of the buyers guide for more).
It seems to me that IF Porsche had redistributed the coolant so more went throught the blocks, fitted rings to the tops of the Lokasil cylinders (to close the deck) and ran with a lower temperature thermostat - we would be seeing few or no scored bores and cylinders cracking much later at higher mileages.
At least my car proves how good they can be rebuilt (and our customers tell us the same - cars crisper and more responsive after rebuild).
The 3.6's and 3.8's are wearing through the white metal on the big ends after around 50 or 60K (there seems to be no copper or bronze as the earlier ones had) and many rebuilds show this wear although the crankshaft is still OK (but would not be for much longer).
I think that these engines (that perform brilliantly when right) may become ones that eventually everyone accepts the wisdom of a rebuild at around 50 or 60K before the cylinders get cracked and can be remanufactured with a closed deck, or the cranks give up and built with with new pistons and shells and increased coolant cylinder block flow and lower temperature thermostat.
Time will tell but we are gearing up in this belief and continuing to invest in engine rebuilding machinery and staff to be managed entirely under our control to maintain the lowest cost and best quality available.
Baz
ber
If you read the buyers guide section 4 (www.hartech.org) you will find that the earlier cars had thicker liners up until the 3.4 (which was the 3.2 block bored out an extra 3mm so 1.5mm thinner wall thickenss (made worse by the fact that half is LOKASIL which is less strong and thermally unstable compared to aluminium).
The 3.4's therefore migrate oval more and sooner and eventually crack. The 3.6's and 3.8's are similar to the 3.4 (despite the extra loads) and run hotter - because more coolant is diverted through the heads and less through the cylinders(and we have just had the first 3.8 with a cracked bore - so it gets you one way or the other). The 3.8 has less space for the coolant (although this in itself may not be a bad thing).
On the other hand Lokasil (if only it was stabilised) is a superb material. it doesn't wear - just distorts if not restrained. My own 155K 996 tiptronic came in with a cracked liner @ 153K was rebuilt with original rings and pistons with 5 bores re-rounded and one liner and changed to a closed deck.
It has been smelling a little bit oily but then I only use it for 4 miles to work and back and the exhausts were full of oil (from the craked liner and oval bores) but after this trip that has stopped. I have just driven it to Brands Hatch and back (540 miles round trip including the M25 round London twice) and it returned 27.4mpg (driving as fast as the law lets you get away with and in the daytime and twice in the rush hour round London) and used hardly any oil - but it does have the lower temperature thermostat (ran @ 79 the whole time).
The problem with other solutions (like bigger or faster pumps or more air through the radiators etc) is that the thermostat restricts the flow until it reaches the set temperature and if this is high - all that will do is slow down the flow more.
Even when I was stopped on the M25 the temperature only went up to 83 (don't forget this is not what you see on the dash board but from the Air con setting digital and accurate reading) whereas with the old thermostat it would be nearer 95 to 100 (but showing far less on the dashboard).
Also please remember that if most of the coolant is going through the heads then the coolant going through the block is less and going much slower and picking up more temperature rise - but when this mixes back with the coolant from the head it minimises the result as it goes back to the thermostat (ref section 5 of the buyers guide for more).
It seems to me that IF Porsche had redistributed the coolant so more went throught the blocks, fitted rings to the tops of the Lokasil cylinders (to close the deck) and ran with a lower temperature thermostat - we would be seeing few or no scored bores and cylinders cracking much later at higher mileages.
At least my car proves how good they can be rebuilt (and our customers tell us the same - cars crisper and more responsive after rebuild).
The 3.6's and 3.8's are wearing through the white metal on the big ends after around 50 or 60K (there seems to be no copper or bronze as the earlier ones had) and many rebuilds show this wear although the crankshaft is still OK (but would not be for much longer).
I think that these engines (that perform brilliantly when right) may become ones that eventually everyone accepts the wisdom of a rebuild at around 50 or 60K before the cylinders get cracked and can be remanufactured with a closed deck, or the cranks give up and built with with new pistons and shells and increased coolant cylinder block flow and lower temperature thermostat.
Time will tell but we are gearing up in this belief and continuing to invest in engine rebuilding machinery and staff to be managed entirely under our control to maintain the lowest cost and best quality available.
Baz
ber
Just a few photos of recent engine work.
(1) Flaked and seized/scored pistons
(2) A new slightly oversized piston fitted.
(3) Crankcase blocked with overspill sealant wearing out a main bearing.
Hoping I have managed the upload correctly (I am not very good at it - sorry if it doesn't come out).
Baz
(1) Flaked and seized/scored pistons
(2) A new slightly oversized piston fitted.
(3) Crankcase blocked with overspill sealant wearing out a main bearing.
Hoping I have managed the upload correctly (I am not very good at it - sorry if it doesn't come out).
Baz
DRP said:
Hi I have noticed a few damp patches on my drive, its not oil but more like the window wash or antifreeze? any ideas?
997 s 05
Could be radiators or expansion tank leaks,may just be wear and tear on rads but may be presurising system I would recommend a OPC/good indy check it over ASAP.HTH997 s 05
Edited by DRP on Tuesday 12th April 18:17
G
tonikaram said:
All,
Let's establish a ratio. All those who owned a 996 non GT3/GT2, please just reply to this thread with the year model, how many years of ownership, and whether the engine failed.
I'm getting to the bottom of this!
Kay
06/997c2sLet's establish a ratio. All those who owned a 996 non GT3/GT2, please just reply to this thread with the year model, how many years of ownership, and whether the engine failed.
I'm getting to the bottom of this!
Kay
19000 miles
full service history
scored bores the usual problem.
no warranty porsche not interested
sorry for earlier post
its a shame you cant edit out the conversations easily and get your stats maybe start a few threads with different models and try to separate failures.
I don't have a problem with people posting that their car is OK but it does seem to me that there will be lots with no problems whatsoever and there will also be some with problems that do not yet show any symptoms and then there are a few that have already failed and it is clear they need repairing or replacing. It is also logical that all those with problems could have previously posted that their car is OK (before the problem emerged) so I am not sure what value can be attatched to the statement except - if you like - "so far so good - fingers crossed"
Although I understand why some people would like to believe that ALL the cars are perfect and therefore see a need to post that they are OK - this may be useful if it proved that none ever go wrong (and therefore they are a great car to own) but since it is perfectly clear that a small number have predictable faults that have been analysed and understood - can be repaired and improved - the more important issues are for those with the problem - or concerned they may have the first signs - or want to improve their odds of avoiding it - to learn what solutions and advice is out there - to empower them to make the best decisions for them, their circumstances and their future plans for their car.
In this respect I cannot see a great deal of value for them in stating that a particular car is OK just now (if indeed it actually is) except perhaps to rub salt in the wounds of those with problems, dissilousionment and expense to deal with.
Baz
Although I understand why some people would like to believe that ALL the cars are perfect and therefore see a need to post that they are OK - this may be useful if it proved that none ever go wrong (and therefore they are a great car to own) but since it is perfectly clear that a small number have predictable faults that have been analysed and understood - can be repaired and improved - the more important issues are for those with the problem - or concerned they may have the first signs - or want to improve their odds of avoiding it - to learn what solutions and advice is out there - to empower them to make the best decisions for them, their circumstances and their future plans for their car.
In this respect I cannot see a great deal of value for them in stating that a particular car is OK just now (if indeed it actually is) except perhaps to rub salt in the wounds of those with problems, dissilousionment and expense to deal with.
Baz
tonikaram said:
All,
Let's establish a ratio. All those who owned a 996 non GT3/GT2, please just reply to this thread with the year model, how many years of ownership, and whether the engine failed.
I'm getting to the bottom of this!
Kay
I was just replying to the opening request in the tread which asked for a ratio, which would require positive as well as negative experiences, apologies if the tread had moved on sinceLet's establish a ratio. All those who owned a 996 non GT3/GT2, please just reply to this thread with the year model, how many years of ownership, and whether the engine failed.
I'm getting to the bottom of this!
Kay
Globs said:
Bubbles formed in boiling water will be pure H2O as a gas (also called steam).
Just think about nitrogen as a gas, then think about liquid nitrogen - you've probably seen that as a liquid on TV. Nitrogen is usually found as a gas because its boiling point is -195.8 °C.
The only difference is that water is usually a liquid at our temperatures and has to be heated to 100C (a normal pressure) become a gas.
But the coolant is not just water is it what chemical would the gas vapour given of by any ethanol based (I think thats correct)be Im sure its not just H20?Just think about nitrogen as a gas, then think about liquid nitrogen - you've probably seen that as a liquid on TV. Nitrogen is usually found as a gas because its boiling point is -195.8 °C.
The only difference is that water is usually a liquid at our temperatures and has to be heated to 100C (a normal pressure) become a gas.
G
No disrespect meant to anyone but these threads dont half go off topic and im sure everyone has a point to make about there car thats valid but I would think Tonikaram probably left the thread ages ago
isnt this exactly what porsche want with these forums ,all of use swaying off topic so theres no quantifiable conclusion to these failing engines
isnt this exactly what porsche want with these forums ,all of use swaying off topic so theres no quantifiable conclusion to these failing engines
Technicaly maybe, but I must confess as someone who has to understand what actually causes this! I have found this to be one of THE most imformative threads posted on any forum inc rennlist ect regarding the issues faced .
I have found particularly Bazs replys and indepth explanations for these issues informative and on topic I for one commend him for donating his free time to monitor and post on these forums to help us understand.I feel at least Im on the right track with my understanding of these engines and assosiated issues.
Thanks again
G
I have found particularly Bazs replys and indepth explanations for these issues informative and on topic I for one commend him for donating his free time to monitor and post on these forums to help us understand.I feel at least Im on the right track with my understanding of these engines and assosiated issues.
Thanks again
G
As a potential 996 owner I've read the posts here and the notes on Baz's site and am wondering if getting one is a good idea!
I'd like a 2002 3.6 manual,(lapis blue, dark interior with toys) so do I try and find one with a rebuilt engine or get one and take out good insurance,or just push the price down expecting to have to pay out 5-6K on a build at some time?
I have access to a boroscope!
It would be a daily driver.
Thoughts please
I'd like a 2002 3.6 manual,(lapis blue, dark interior with toys) so do I try and find one with a rebuilt engine or get one and take out good insurance,or just push the price down expecting to have to pay out 5-6K on a build at some time?
I have access to a boroscope!
It would be a daily driver.
Thoughts please
BobM2 said:
As a potential 996 owner I've read the posts here and the notes on Baz's site and am wondering if getting one is a good idea!
:
Thoughts please
My opinion of this (996/997/986/987) is that we know an expert who can rebuild them to a proper standard: better than new, and the rest of the car is rust free, good looking and well designed.:
Thoughts please
I.e: Imagine buying an expensive Mercedes and watching it rust away - there really is no cure for that, but with the affordable prices of the water cooled porsches if all you have to worry about is an engine rebuild - perhaps at the end of the day it's still out there ahead of many many other cars. So I think you should take account of the issue and price it into the deal. If you do ever need the engine rebuilt by Hartech etc then that would be a positive selling point IMO.
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