Are 997.1 3.6 engines more reliable than 3.8 engines? - Page 1 - Porsche General - PistonHeads UK

I'm considering a 997 at the moment and was wondering if there are more reliability issues associated with the Carrera S 3.8 compared to the Carrera 3.6? I know they both suffer from IMS bearing (serious) and RMS (less serious) issues to some degree, but are each just as likely to have a problem, given that the 3.6 is a bit less powerful (less stressed block?) and the more tried and tested version of the engine, with only minor mods since 2001. Also, I've read about bore scoring issues related to overheating (cylinders 5 and 6 maybe?) but this appears to be mainly on the 3.8 997 and not so common on the 3.6 engine through the 996 and 997 range. Perhaps this is a misconception based on cases I've seen... Any thoughts or evidence on this appreciated.

Hi there The issues are pretty rare to be honest, but the 3.8 is more likely to suffer from bore scoring than the 3.6 from what I've read. It would seem best to avoid cars which have being garage queens or likely to have being driven in heavy traffic i.e. London as the issues seem to be effecting cars which are stuck, well in traffic. Baz who knows more has said its basically good for these cars to get driven properly and regular, also the third radiator is a very good option as its heat which are these engines big problem.

Thanks, anyone with any more info on this?

Assuming the engine is fine when you buy, from OPC with 2 year warranty or other with inspection. 1. Keep revs down until engine fully up to working temperature and thermostat is open. 2. Get a low temperature thermostat fitted from Hartech or Autofarm. 3. Stop worrying and enjoy.

To be more specific - the problem does not seem to exist when he cars are revved it seems worse (as already correctly stated) if the temperatures vary too much and run temporarily too high at the same time as a lot of low revs but fully open throttle causes high torque and high piston loads between the piston face and the Lokasil bore material while the oil is too thin to support the two metals sufficiently. As the 3.6 has less torque and less heat to dissipate and also because it also has a larger coolant gallery near the cylinder walls - it should suffer less often (and numbers seem to support this but then that may also relate to the lower sales figures - it is really difficult to be objective with such statistics. Still very few fail and the cost of repair for those that do is not too bad when you consider the benefits and improvements that can also be applied and the relatively low purchse prices that the worry about all this has resulted in. furthermore they are reaching an age where 911 SC's often snapped cylinder studds, 964's leaked head joints, and even some 944's ran the number 2 big ends etc. I agree - buy and enjoy - but then - while Grant and I have done just that - I suppose we could not be in a better position if ours failed (could we) especially as they tend to arrive with engines already gone and then form part of our own internal research and development plans and therefore have all the latest mods. Baz

Thanks for the responses, which are very helpful.

It’s been a while Baz. I’m a new member and a new owner of a 2006 997.1 Carrera. I am doing endless searching on the site regarding score boring. Do you still believe that the 3.6 engine is less likely to score. I have 31000 miles and had the oil analyzed with no metal found. But I’m still concerned. Any new input to shed light on this issue. Thanks Rob

Rzau said: It’s been a while Baz. I’m a new member and a new owner of a 2006 997.1 Carrera. I am doing endless searching on the site regarding score boring. Do you still believe that the 3.6 engine is less likely to score. I have 31000 miles and had the oil analyzed with no metal found. But I’m still concerned. Any new input to shed light on this issue. Thanks Rob Released last weekend : https://www.youtube.com/watch?v=G7idZe6qAtg&t=... https://www.youtube.com/watch?v=U_K_XkXx1Tw https://www.youtube.com/watch?v=-xbPE3YVy3k https://www.youtube.com/watch?v=3E4VFBqnZiU

Thanks for your input.

Slippydiff said: Released last weekend : https://www.youtube.com/watch?v=G7idZe6qAtg&t=... https://www.youtube.com/watch?v=U_K_XkXx1Tw https://www.youtube.com/watch?v=-xbPE3YVy3k https://www.youtube.com/watch?v=3E4VFBqnZiU Slippy - is it 4x25 mins and is it really worth spending an hour on? (I clicked on the first link and saw it was 25 mins!) The OP's post is definitely making me reconsider a 3.6 997.1

braddo said: Slippydiff said: Released last weekend : https://www.youtube.com/watch?v=G7idZe6qAtg&t=... https://www.youtube.com/watch?v=U_K_XkXx1Tw https://www.youtube.com/watch?v=-xbPE3YVy3k https://www.youtube.com/watch?v=3E4VFBqnZiU Slippy - is it 4x25 mins and is it really worth spending an hour on? (I clicked on the first link and saw it was 25 mins!) The OP's post is definitely making me reconsider a 3.6 997.1 It is indeed 4 x 25 minute videos. But it's the best summation on M96/97 bore scoring, what causes it, how to diagnose it (and this was an eye-opener) how to avoid it, how to fix it etc etc I've seen to date. Charles Navarro of LN Engineering and Lake Speed, Jr. of Total Seal Piston Rings are probably THE most knowledgeable individuals in the US (along with Jake Raby) on the bore scoring issues that affect the M96/97 motors.

I posted a link to PCA tech-talk with these guys linking bore scoring with ethanol back in february. The PCA seem to have dropped that video - 'How To Keep Your Porsche Engine Running Right: Oils, Fuel, and Oil Analysis | Tech Tactics Live'

Orangecurry said: I posted a link to PCA tech-talk with these guys linking bore scoring with ethanol back in february. The PCA seem to have dropped that video - 'How To Keep Your Porsche Engine Running Right: Oils, Fuel, and Oil Analysis | Tech Tactics Live' Interesting, what conclusions did they come to ?? IIRC the suggestion was (in one of the four videos I’ve linked to) that ethanol was responsible for damaging/clogging the injector pintles and that in turn was causing irregular spray patterns and leaking/dribbling injectors, both of which can lead to bore-washing and in turn bore-scoring.

Not sure they said anything about 'damaging' the injectors in the earlier video, but they did say that higher-ethanol content caused the petrol air mix not to atomise as well as with no/lower-ethanol fuels, and this did lead to bore washing... from memory. (edited for clarity) Edited by Orangecurry on Friday 7th April 19:43

Thank you Cossers. Will do.

it was indeed a good set of info. -fuel is important, use good fuel, high grade, not eco fuel. -faulty bad spraying injectors can cause washing oilfilm away -faulty/leaky hoses air and sort, can cause bad fuel mix, to rich = washing oilfilm away -also something about some type pistons -also something about which age of those problems, mostly ages before 2008/09? forgot about a few things though, was a few days ago when I saw them, some sounded very logical, like the washing the protecting oilfilm away by the wrong or to much fuel mix things when they explained those.

Interesting vids. May have missed some bits, but from a quick scan through and for what it is worth seems to be some divergence from Hartech's take on the scoring thing. Not an engine builder so don't really know who is correct, but I think Hartech places more emphasis on cooling asymmetry, the placement of the thermostat on the inlet of the cooling circuit, the oil film breaking down in the hotter running cylinders, promoting direct skirt to bore contact and also small fragments of the Lokasil material being ejected from the bore surface, being trapped between the bore and piston and damaging the piston skirt coating, which then starts the process of the coating breaking down. I think this video talks about the skirt sticking out below the bottom of the bore and getting chipped away (by the edge of the bore bottom?) as the piston rocks a tiny bit as it goes through the bottom of the stroke. Hartech talks about changes in the Lokasil material over the life cycle of the M96/7 run, with the later engines' bore material more prone to ejecting particles, which then start the process of the piston coating being damaged. These videos did note that you get more problems in colder running climates, which is a consequence of the weird thermostat location, I think, and relates to overheating in bank two. The videos seemed to have a more mechanical explanation for bank two being much more prone to scoring which didn't really account for the cold climate thing or the cooling asymmetry. Anyway, I may have missed a few things, but seemed like some divergence in view. The Hartech narrative as I understand it probably seems more coherent to me, but at the very least the whole thing is obviously pretty complex.