Discussion
Just found a beautiful 2005 911 carrera 2 S 40k mileage but a very similar car mentions having had the " all important score bore " done at 52k is this something I need to be concerned about having done in the next 10 - 20k miles sounds a big job at £10k after spending £30k to buy the car in the 1st place
Thanks
Thanks
The car I'm hoping to purchase hasn't had anything done apart from regular Porsche servicing but a similar car with a higher mileage has had a bore score done my question is
Do the 3.8 engine cars require this bore score done around the 50 - 60 k miles and is this the reason a lot of cars come up for sale around this mileage.
Do the 3.8 engine cars require this bore score done around the 50 - 60 k miles and is this the reason a lot of cars come up for sale around this mileage.
Two technical changes (and a capacity increase) combined to create a problem with this model range.
(1) Bore surface of all M96/7 engines was changed to "Lokasil" (Boxster, 996, 997 Gen 1, Cayman) a new process described as if it was the same as the previously successful "Alusil" (944, 924S, 968) that worked well when combined with a hard ferrous piston coating.
However it seems that this bore surface was less strong (so could allow the bore to gradually move oval over time - especially if the wall thickness was thin) was less consistent in the distribution of the hard particles of silicon and that it released more surface particles over time that were momentarily trapped between the piston and the cylinder bore before escaping in the oil.
As bigger bore engines were squeezed into the same layout - the space for coolant diminished and the cylinder wall thickness was reduced to compensate - resulting in the cylinders being less stiff while the forces pressing the piston against the cylinder wall and any released hard particles increased with the power increase with bores distorting oval and eventually cracking.
This reduced the reliability of the new Lokasil bore engines as mileages increase with problems usually occurring around 40 to 60 K (scoring) but the scoring does not usually stop the engine working and is only on one side of the piston and can run for several thousand miles more before it is obvious and needs fixing.
To make the thinner cylinders stiffer (to reduce creeping ovality) it seems that a different version of Lokasil (Lokasil 2) may have been introduced with bigger silicon particles - but while this achieved that objective any particles that became lose and trapped between the piston and cylinder wall were then bigger and could cause more damage.
(2) Early Boxster and M96 3.4 engines had the same type of ferrous (iron) coated pistons that were previously used successfully with Alusil and didn't score. The bores in 3.2 and smaller engines were also thicker and therefore didn't distort or crack. This fact combined with less power pushing the piston against the cylinder wall resulted in a reliable new Lokasil/ferrous coated piston combination.
However we are informed that the process of plating the pistons was outlawed and that a plastic coating replaced the ferrous coating that is less hard (especially when the piston and coating are hot). The last M96 3.4 engines had plastic coated pistons - as did the Cayman (& S), 3.4 Boxster (& S), and M96/7 3.6 and 3.8 engines. We think that Lokasil 2 may also have been used then as well.
The bigger the capacity - the harder the plastic coated piston pushes against the cylinder wall and the more it will distort the bore and work silicon particles loose. The result is greater piston coating wear rates the larger the capacity and of course the harder the engine has been driven.
If a graph were drawn of capacity against average reliability it would simply show that the earliest Boxster small capacity engines (with ferrous coated pistons and thick cylinder walls) were perfectly reliable (not talking about IMS issues here), all engines with Ferrous coated pistons didn't score bores but the larger capacity versions had cylinders moving oval and eventually cracking (so would appear more towards the unreliable end).
When plastic coated pistons were used, smaller capacity engines (with thicker bores and less forces pushing the piston against the cylinder wall) seemed to last well (so would be nearer the reliable end) but as capacity increased (3.4 and above) the wear rate on piston coatings increased and more appear nearer the unreliable end of the graph with the 3.4 Cayman S, 3.6 and 3.8 filling the places in sequence towards the extreme unreliable end.
Variations in the distribution of the silicon in the engine castings, quality of maintenance, frequency of oil changes, grade and type of oil, user style (aggressive or modest) all contribute to the mileage where the scoring occurs and then how long it takes before anyone realises it to be a problem also influence the statistics that may be recorded - making accurate predictions impossible. We can only estimate the averages but there are always extremes in both directions.
If a cylinder bore is checked with a camera it will not disclose how far worn the piston coating is (and some even have the coating flake off) nor how secure the remaining silicon particles are still held in the cylinder bore matrix - so although a boroscope may show an unscored bore - failure may still be imminent.
At the same time the GT3 and Turbo versions had an alloy cylinder with a Nikasil plated surface and gave no unreliability piston/cylinder problems and so it is reasonable to conclude that if these had been fitted to this range of N/A engines it would have eliminated all these problems (although been more expensive).
When we replace the Lokasil liners with alloy Nikasil cylinders - our rebuilt engines enjoy the superb level of cylinder reliability and performance of those GT3 and Turbo engines resulting in a reliable repair that could have been how they were made in the first place if production cost was less of an issue.
Baz
(1) Bore surface of all M96/7 engines was changed to "Lokasil" (Boxster, 996, 997 Gen 1, Cayman) a new process described as if it was the same as the previously successful "Alusil" (944, 924S, 968) that worked well when combined with a hard ferrous piston coating.
However it seems that this bore surface was less strong (so could allow the bore to gradually move oval over time - especially if the wall thickness was thin) was less consistent in the distribution of the hard particles of silicon and that it released more surface particles over time that were momentarily trapped between the piston and the cylinder bore before escaping in the oil.
As bigger bore engines were squeezed into the same layout - the space for coolant diminished and the cylinder wall thickness was reduced to compensate - resulting in the cylinders being less stiff while the forces pressing the piston against the cylinder wall and any released hard particles increased with the power increase with bores distorting oval and eventually cracking.
This reduced the reliability of the new Lokasil bore engines as mileages increase with problems usually occurring around 40 to 60 K (scoring) but the scoring does not usually stop the engine working and is only on one side of the piston and can run for several thousand miles more before it is obvious and needs fixing.
To make the thinner cylinders stiffer (to reduce creeping ovality) it seems that a different version of Lokasil (Lokasil 2) may have been introduced with bigger silicon particles - but while this achieved that objective any particles that became lose and trapped between the piston and cylinder wall were then bigger and could cause more damage.
(2) Early Boxster and M96 3.4 engines had the same type of ferrous (iron) coated pistons that were previously used successfully with Alusil and didn't score. The bores in 3.2 and smaller engines were also thicker and therefore didn't distort or crack. This fact combined with less power pushing the piston against the cylinder wall resulted in a reliable new Lokasil/ferrous coated piston combination.
However we are informed that the process of plating the pistons was outlawed and that a plastic coating replaced the ferrous coating that is less hard (especially when the piston and coating are hot). The last M96 3.4 engines had plastic coated pistons - as did the Cayman (& S), 3.4 Boxster (& S), and M96/7 3.6 and 3.8 engines. We think that Lokasil 2 may also have been used then as well.
The bigger the capacity - the harder the plastic coated piston pushes against the cylinder wall and the more it will distort the bore and work silicon particles loose. The result is greater piston coating wear rates the larger the capacity and of course the harder the engine has been driven.
If a graph were drawn of capacity against average reliability it would simply show that the earliest Boxster small capacity engines (with ferrous coated pistons and thick cylinder walls) were perfectly reliable (not talking about IMS issues here), all engines with Ferrous coated pistons didn't score bores but the larger capacity versions had cylinders moving oval and eventually cracking (so would appear more towards the unreliable end).
When plastic coated pistons were used, smaller capacity engines (with thicker bores and less forces pushing the piston against the cylinder wall) seemed to last well (so would be nearer the reliable end) but as capacity increased (3.4 and above) the wear rate on piston coatings increased and more appear nearer the unreliable end of the graph with the 3.4 Cayman S, 3.6 and 3.8 filling the places in sequence towards the extreme unreliable end.
Variations in the distribution of the silicon in the engine castings, quality of maintenance, frequency of oil changes, grade and type of oil, user style (aggressive or modest) all contribute to the mileage where the scoring occurs and then how long it takes before anyone realises it to be a problem also influence the statistics that may be recorded - making accurate predictions impossible. We can only estimate the averages but there are always extremes in both directions.
If a cylinder bore is checked with a camera it will not disclose how far worn the piston coating is (and some even have the coating flake off) nor how secure the remaining silicon particles are still held in the cylinder bore matrix - so although a boroscope may show an unscored bore - failure may still be imminent.
At the same time the GT3 and Turbo versions had an alloy cylinder with a Nikasil plated surface and gave no unreliability piston/cylinder problems and so it is reasonable to conclude that if these had been fitted to this range of N/A engines it would have eliminated all these problems (although been more expensive).
When we replace the Lokasil liners with alloy Nikasil cylinders - our rebuilt engines enjoy the superb level of cylinder reliability and performance of those GT3 and Turbo engines resulting in a reliable repair that could have been how they were made in the first place if production cost was less of an issue.
Baz
WOW Baz that reply was excellent thank you, I have been looking for a nice 2005 upwards, low milage 911 carrera 4 S for a while and found one but during my search had noticed a couple had had the bore scopes done at around 50 to 60 k and repaired at a cost of £10k the one I found only had 30k on the clock and was concerned that in another 20k miles I would expect to pay out another £10k for engine work which is not in my budget, so thank you again I shall not waste any more time looking at Porsche.
Edited by highflyer on Tuesday 2nd May 08:29
highflyer said:
WOW Baz that reply was excellent thank you, I have been looking for a nice 2005 upwards, low milage 911 carrera 4 S for a while and found one but during my search had noticed a couple had had the bore scopes done at around 50 to 60 k at a cost of £10k the one I found only had 30k on the clock and was concerned that in another 20k miles I would expect to pay out another £10k for engine work which is not in my budget, so thank you again I shall not waste any more time looking at Porsche.
Woah hold your horses a second there. Ignoring the fact that scored bores and blown IMS valve discussion is rife on here and on specialist Porsche boards how many engines do you think are really damaged over the tens of thousands built? People don't go on the internet to proclaim that their engine is brilliant and not scored. What makes you think that the BMW / Mercedes / Ferrari etc that you will buy instead of a Porsche will be any more reliable and not need 10k of work in 20k miles time?
ALL cars have their issues and you can't entirely protect yourself from them. Buy the car you want and get a decent warranty if it concerns you. Or never own a Porsche because someone on the internet once said they score their bores. Your choice.
highflyer said:
WOW Baz that reply was excellent thank you, I have been looking for a nice 2005 upwards, low milage 911 carrera 4 S for a while and found one but during my search had noticed a couple had had the bore scopes done at around 50 to 60 k at a cost of £10k the one I found only had 30k on the clock and was concerned that in another 20k miles I would expect to pay out another £10k for engine work which is not in my budget, so thank you again I shall not waste any more time looking at Porsche.
Hold on a little minute or two. Translating Baz explanation into a buyers guide. If you think a cheap £20k 997 is without risk think again. However if you are figuring on spending about £30k then all is fine. A cheap 997 with higher mileage factoring in rebuild, or a £30k car which is bore checked and low mileage.My 65k miles 997 was £20k a couple of years ago. But I do have in the back of my head a possible 10k bill.
As long as you don't buy a 30k unchecked car all should be fine.
If you want a 20k limited risk car then it's an earlier 996 or a boxster Cayman route.
This thread is a nice example of a little knowledge ..........
If the buyer is risk adverse and there is a "chance" of bore scoring with the inevitable large bill, then I can understand his reasons for not proceeding further.
Even after owning 3 911's to date, I wouldn't entertain buying a Porsche out of warranty. From memory was it a 5% chance of IMs failure on earlier cars ? Not sure what % risk it is with bore scoring. Not all owners will go on to a public forum to state they have had problems, so hard to say.
And yes, other manufacturers have their problems too, before I get shot down
Even after owning 3 911's to date, I wouldn't entertain buying a Porsche out of warranty. From memory was it a 5% chance of IMs failure on earlier cars ? Not sure what % risk it is with bore scoring. Not all owners will go on to a public forum to state they have had problems, so hard to say.
And yes, other manufacturers have their problems too, before I get shot down
DaveGB said:
And yes, other manufacturers have their problems too, before I get shot down
Of course they do which is what makes the OPs sudden aversion to Porsche laughable. Whatever is purchased in place of it could have just as much of an issue with similar costs or worse.The quoted percentage about IMS being 5% is probably about right but if we all didn't do something because there was a 5% chance that it may go wrong then we wouldn't do much at all.
The biggest thing to remember is that regardless of how cheap such a car becomes it comes with maintainence and repair bills consummate with its original purchase price.
craigjm said:
The biggest thing to remember is that regardless of how cheap such a car becomes it comes with maintainence and repair bills consummate with its original purchase price.
Very true, although I feel there is a tipping point. I'm currently on 2nd Lotus Evora and although new it was £80k I know from experience and knowledge of car that biggest bill would be a new clutch at circa £3k for a manual (I've gone Auto). I look at McLaren 540c's at £130k new (63% more) , but expect to see a bill larger than £5k down the line. Bloody nice car mind you
Would actually like to have a 997 for a daily runner, as not too flash to clients. But yes, a potential large bill puts me off. I do keep an eye out on Hartech site for any rebuilt cars mind you
highflyer said:
Just found a beautiful 2005 911 carrera 2 S 40k mileage but a very similar car mentions having had the " all important score bore " done at 52k is this something I need to be concerned about having done in the next 10 - 20k miles sounds a big job at £10k after spending £30k to buy the car in the 1st place
Thanks
High flyer, "score bore" / "bore score" are things which go wrong. They cost nothing. They are not things owners choose to get done. Thanks
Bore scope is a check you can get done to see whether bore scoring is happening. It costs a few hundred pounds. It does not make things better, or worse.
A rebuild is the only way to repair bore scoring. It costs thousands.
if you bought a car under 80K that has not yet scored it could be eligible for our maintenance Plan which minimises the cost of an engine rebuild. Or there are other reliable ways to protect costs if it fails.
They are brilliant cars and great engines. Many will have been maintained and driven in such a way that they will exceed the mileages generally quoted.
However the originator is right to walk away if his budget will not cover buying an unscored car nor paying for a rebuild (even when some form of protection reduces the bill).
Or you could buy a higher mileage one at lower cost and use the balance to have a reliable pre-emptive rebuild that will add value to the car and provide reliable service.
There are a lot of specialists providing rebuilds - not all are as reliable as others and not all are using more proven, long term specifications nor are well organised enough to carry out so many rebuilds each week that if a warranty claim did materialise - they can easily afford to fit into their production schedule - the subsequent repair - so some would make life more difficult than others if their rebuild had resulting problems.
Personally I think buying a high mileage one that is running perfectly OK and having a pre-emptive rebuild is a better solution than what appears to be allow mileage example that could still be work out internally even if it does not yet show signs of bore scoring.
Baz
They are brilliant cars and great engines. Many will have been maintained and driven in such a way that they will exceed the mileages generally quoted.
However the originator is right to walk away if his budget will not cover buying an unscored car nor paying for a rebuild (even when some form of protection reduces the bill).
Or you could buy a higher mileage one at lower cost and use the balance to have a reliable pre-emptive rebuild that will add value to the car and provide reliable service.
There are a lot of specialists providing rebuilds - not all are as reliable as others and not all are using more proven, long term specifications nor are well organised enough to carry out so many rebuilds each week that if a warranty claim did materialise - they can easily afford to fit into their production schedule - the subsequent repair - so some would make life more difficult than others if their rebuild had resulting problems.
Personally I think buying a high mileage one that is running perfectly OK and having a pre-emptive rebuild is a better solution than what appears to be allow mileage example that could still be work out internally even if it does not yet show signs of bore scoring.
Baz
Thank you for all the constructive information, well most of it, I do understand the difference between a bore scope and a bore score one being a preventative measure the other being a problem to be solved and the two differences in costs.
I am not looking to spend between £30 - £40k for a car that could potentially cost me a further £10k in 20 to 30 thousand miles down the line and im not sure a seller would be happy to spend £100-£200 to have his car checked out.
I have owned 5 Ultimas 2 Can-Am 3 GTR's over the last 10 years (in between atom 300 Lotus and Ferrari P4) never had an issue because I drive and use them not like most which are constantly tinkered with garage queens, the reason I have had so many is because I get bored, sell then realize that there isn't anything else out there with the looks, performance and ability to work on yourself without having to go to a specialist so I end up buying another one but this time I fancied a change and was going down the Porsche route, having looked further into Porsche ownership and other issues seem to pop up on a regular basis, so i'm moving onto another marque.
Thanks again for the info
I wont bang my arse on the way out A.G
I am not looking to spend between £30 - £40k for a car that could potentially cost me a further £10k in 20 to 30 thousand miles down the line and im not sure a seller would be happy to spend £100-£200 to have his car checked out.
I have owned 5 Ultimas 2 Can-Am 3 GTR's over the last 10 years (in between atom 300 Lotus and Ferrari P4) never had an issue because I drive and use them not like most which are constantly tinkered with garage queens, the reason I have had so many is because I get bored, sell then realize that there isn't anything else out there with the looks, performance and ability to work on yourself without having to go to a specialist so I end up buying another one but this time I fancied a change and was going down the Porsche route, having looked further into Porsche ownership and other issues seem to pop up on a regular basis, so i'm moving onto another marque.
Thanks again for the info
I wont bang my arse on the way out A.G
That's right - the Gen 2 engines are far superior.
However the 5 crankcase sets we have had here to measure that have scored were all from 3.8's and had all gone oval in the opposite direction as a result of age related stress relieving - all cylinders 1 and 4 with cylinders 2 and 5 half the amount of ovality and cylinders 3 and 6 OK.
With tight piston clearances to start with we they eventually pinch the piston during fast warm up before the cylinders have expanded as much as the pistons.
We cannot tell if the fault is common yet or will gradually afflict all versions but we did yesterday have an enquiry about a scored smaller capacity version and it was also cylinder 1 and/or 4.
We have designed and developed a solution soon to be assembled and tested but are interested to hear about all 9A1 failures from feedback please.
Baz
However the 5 crankcase sets we have had here to measure that have scored were all from 3.8's and had all gone oval in the opposite direction as a result of age related stress relieving - all cylinders 1 and 4 with cylinders 2 and 5 half the amount of ovality and cylinders 3 and 6 OK.
With tight piston clearances to start with we they eventually pinch the piston during fast warm up before the cylinders have expanded as much as the pistons.
We cannot tell if the fault is common yet or will gradually afflict all versions but we did yesterday have an enquiry about a scored smaller capacity version and it was also cylinder 1 and/or 4.
We have designed and developed a solution soon to be assembled and tested but are interested to hear about all 9A1 failures from feedback please.
Baz
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