997 cylinder liners
Discussion
ro_butler said:
DSM2 said:
A 0-40 will be less viscous than a 5-40 when cold. They will have equal viscosity when hot, which is when it really matters in terms of holding pressure and perhaps not burning it.
That's the theory. Didn't seem to pan out that way for me. If I change to 0w-40 my oil consumption increases and oil pressure at hot idle is lower..... (suggesting to me lower viscosity). The shear strength may not be compromised but that is impossible for me to check.bcnrml said:
They all need gentle treatment when cold. Ten minutes (as some continue to argue) is not long enough to warm up an engine in the UK's climate.
Amen to that!! The number of nice cars I have seen being thrashed to death coming out of Canary Wharf (presumably after being parked up all day) beggars belief 
ro_butler said:
DSM2 said:
A 0-40 will be less viscous than a 5-40 when cold. They will have equal viscosity when hot, which is when it really matters in terms of holding pressure and perhaps not burning it.
That's the theory. Didn't seem to pan out that way for me. If I change to 0w-40 my oil consumption increases and oil pressure at hot idle is lower..... (suggesting to me lower viscosity). The shear strength may not be compromised but that is impossible for me to check.Perhaps your observations are more to do with the age of the oil?
I can honestly say that I have never had oil pressure or consumption issues with any car I have owned from new. Over about 35 years that is quite a number, petrol, diesel and various makes and milages up to and over 90K.
I put that down to sympathetic running in and careful warm ups.
My 911 takes 6 to 8 miles to get the oil up to 90c. It is really no hardship to take it easy for that period of time.
Having said this, I have seen test reports that indicate that Mobil 1, in any grade, is far from the best oil available in terms of film strength, which is what really matters.
Yup I did understand how the oil viscosity range works and that they are basically saying that at normal running temperatures it should be as good as a 40 grade whether it is a 0-40 or 10-40 or 5-40 but this depends on that running temperature and without doubt as oil gets hotter the viscosity falls. In my experience that is not the case by just simply seeing it drip or pour when hot and anyway - it seems very thin and the 10-40 etc seems thicker - but anyway I think we are missing a rather obvious point - that runs throughout this posting.
It is always a mistake when people with experience find out something from experience - to just rubbish what they found out by some technical argument that appears to appose it. People don't run engines with something less good than something else - they always want the best and if someone finds out that one grade of oil gives better performance than another - they don't have any unlterior motive for suggesting that and have nothing to gain from doing so - but failure if they are wrong.
I really get anoyed when people who have not experimented with different oils (and the same applies to lots of different technical issues) argue against someone who has on the grounds of some accademic empirical rule they believe in but have never tested. I have found (and so has any successful development engineer anywhere involved in racing or engines) that if experience shows up a trend - you absolutely must take note of it and act accordingly - even if you don't understand it yet - because there is always an explanation that eventually emerges.
It is OK to discuss and even dissagree on what might be the reason behind all sorts of phenomenon but never doubt that the phenomeon exists or consider that the solution or improvement found by several people was actually some blind mindless mistake and that they actually made things worse but didnt't notice it.
Right throughout the history of the problems with these engines we have quickly and successfully found the right solutions. They were based on our technical conclusions that we often openly convey to others. However the conclusions may be wrong or misguided in some cases - but if the solutions actually work - it doesn't matter if the reasoning was a bit out (not that I think it was) as much as the solutions working (which they all do).
Debate about the reasons behind failures is IMHO good for everyone and sometimes throws up new issues that are of interest - but more often simply finds others who found the same problem and solution worked (as in this case).
Dont forget that the running oil pressure is limited by the oil pressure relief valve - so the running oil pressure may well be the same on the guage - whatever oil is in the engine - but the oil has to travel through hot castings to get to the area it lubricates and by then (like typically when trapped between a piston and cylinder wall that is hotter than say some other engine) will be thinner and a thicker oil may well work better there even if the oil pressure on the guage is the same.
If (as I suspect/believe) the temperature of the coolant coming out of the cylinders is hotter than the greater amount coming out of the heads - before it mixes together again - then if (as I suspect) the cylinders are running hotter than normal (or in more tradditional engines) and especially since the lower half of the cylinder casting is now in contact with crankcase oil (which is taking heat from it) then it is possible that the oil running temperature is hotter than the temperature that the comparative viscosity was taken to list the range for the oil under typical conditions - or in critical parts of the engine.
Furthermore - if we compare the 944 turbo (say) with the 996 - the lower cylinder recieves the coldest coolant directly in the 944 wheras the 996 lower cylinder is not cooled at all by the coolant and the upper cylinder that is cooled by it - receives only a fraction of the amount of coolant the 944 received = the lower cylinder casting must be running hotter in a 996/7 than a 944 and the oil in between the piston and the cylinder must be hotter and therefore thinner. If this is the case then using a higher viscosity oil simply makes the rating between the hotter piston to cylinder wall area - the same as it might have been with a lower viscosity oil in an engine running cooler in that area.
Put simply - the oil might indeed be thinner in parts of this engine and therefore a lower viscosity because the engine is generally running hotter - especially in some areas that oil is in contact with or used as the alternative cooling agent.
Baz
It is always a mistake when people with experience find out something from experience - to just rubbish what they found out by some technical argument that appears to appose it. People don't run engines with something less good than something else - they always want the best and if someone finds out that one grade of oil gives better performance than another - they don't have any unlterior motive for suggesting that and have nothing to gain from doing so - but failure if they are wrong.
I really get anoyed when people who have not experimented with different oils (and the same applies to lots of different technical issues) argue against someone who has on the grounds of some accademic empirical rule they believe in but have never tested. I have found (and so has any successful development engineer anywhere involved in racing or engines) that if experience shows up a trend - you absolutely must take note of it and act accordingly - even if you don't understand it yet - because there is always an explanation that eventually emerges.
It is OK to discuss and even dissagree on what might be the reason behind all sorts of phenomenon but never doubt that the phenomeon exists or consider that the solution or improvement found by several people was actually some blind mindless mistake and that they actually made things worse but didnt't notice it.
Right throughout the history of the problems with these engines we have quickly and successfully found the right solutions. They were based on our technical conclusions that we often openly convey to others. However the conclusions may be wrong or misguided in some cases - but if the solutions actually work - it doesn't matter if the reasoning was a bit out (not that I think it was) as much as the solutions working (which they all do).
Debate about the reasons behind failures is IMHO good for everyone and sometimes throws up new issues that are of interest - but more often simply finds others who found the same problem and solution worked (as in this case).
Dont forget that the running oil pressure is limited by the oil pressure relief valve - so the running oil pressure may well be the same on the guage - whatever oil is in the engine - but the oil has to travel through hot castings to get to the area it lubricates and by then (like typically when trapped between a piston and cylinder wall that is hotter than say some other engine) will be thinner and a thicker oil may well work better there even if the oil pressure on the guage is the same.
If (as I suspect/believe) the temperature of the coolant coming out of the cylinders is hotter than the greater amount coming out of the heads - before it mixes together again - then if (as I suspect) the cylinders are running hotter than normal (or in more tradditional engines) and especially since the lower half of the cylinder casting is now in contact with crankcase oil (which is taking heat from it) then it is possible that the oil running temperature is hotter than the temperature that the comparative viscosity was taken to list the range for the oil under typical conditions - or in critical parts of the engine.
Furthermore - if we compare the 944 turbo (say) with the 996 - the lower cylinder recieves the coldest coolant directly in the 944 wheras the 996 lower cylinder is not cooled at all by the coolant and the upper cylinder that is cooled by it - receives only a fraction of the amount of coolant the 944 received = the lower cylinder casting must be running hotter in a 996/7 than a 944 and the oil in between the piston and the cylinder must be hotter and therefore thinner. If this is the case then using a higher viscosity oil simply makes the rating between the hotter piston to cylinder wall area - the same as it might have been with a lower viscosity oil in an engine running cooler in that area.
Put simply - the oil might indeed be thinner in parts of this engine and therefore a lower viscosity because the engine is generally running hotter - especially in some areas that oil is in contact with or used as the alternative cooling agent.
Baz
I was'nt going to get involved with the oil viscosity arguement but after reading the comments from Baz - here is my tupenny worth.
I know the manufacturers of oil publish a specification for their oil and I'm sure there are exacting tests to prove viscosity both hot and cold BUT in my years of experience of being an end user of their products I have found 0w/40 oils seem to be consumed by engines at a lot faster rate than 10W/40 oils.
If the higher 40W number is the same for both types of oil, anyone with an equiring mind would want to know why??? Something is not consistent with the tests springs to mind. Is the push for lower viscosity oils influenced by a need to demonstrate better fuel economy? Do the tests only have validity on a brand new engine which is up to specification? Do the tests take into account the long term effects that a thinner oil might have at high mileages? Do the manufacturers even care how much oil is consumed?
So, if genuine experience proves to me that my engine rattles less, burns less, maintains better pressure when hot and most importantly lasts longer then I have to say "B-gger the experts"
If I am unable to learn from experience then I will probably become extinct!
Call me a sceptic but I tend to believe what I see and experience for myself rather than rely on what teams of marketeers or academics would like me to believe.
This is what sets engineers apart from hair dressers or telephone sanitizers.
I know the manufacturers of oil publish a specification for their oil and I'm sure there are exacting tests to prove viscosity both hot and cold BUT in my years of experience of being an end user of their products I have found 0w/40 oils seem to be consumed by engines at a lot faster rate than 10W/40 oils.
If the higher 40W number is the same for both types of oil, anyone with an equiring mind would want to know why??? Something is not consistent with the tests springs to mind. Is the push for lower viscosity oils influenced by a need to demonstrate better fuel economy? Do the tests only have validity on a brand new engine which is up to specification? Do the tests take into account the long term effects that a thinner oil might have at high mileages? Do the manufacturers even care how much oil is consumed?
So, if genuine experience proves to me that my engine rattles less, burns less, maintains better pressure when hot and most importantly lasts longer then I have to say "B-gger the experts"
If I am unable to learn from experience then I will probably become extinct!
Call me a sceptic but I tend to believe what I see and experience for myself rather than rely on what teams of marketeers or academics would like me to believe.
This is what sets engineers apart from hair dressers or telephone sanitizers.
Pugley said:
I was'nt going to get involved with the oil viscosity arguement but after reading the comments from Baz - here is my tupenny worth.
I know the manufacturers of oil publish a specification for their oil and I'm sure there are exacting tests to prove viscosity both hot and cold BUT in my years of experience of being an end user of their products I have found 0w/40 oils seem to be consumed by engines at a lot faster rate than 10W/40 oils.
If the higher 40W number is the same for both types of oil, anyone with an equiring mind would want to know why??? Something is not consistent with the tests springs to mind. Is the push for lower viscosity oils influenced by a need to demonstrate better fuel economy? Do the tests only have validity on a brand new engine which is up to specification? Do the tests take into account the long term effects that a thinner oil might have at high mileages? Do the manufacturers even care how much oil is consumed?
So, if genuine experience proves to me that my engine rattles less, burns less, maintains better pressure when hot and most importantly lasts longer then I have to say "B-gger the experts"
If I am unable to learn from experience then I will probably become extinct!
Call me a sceptic but I tend to believe what I see and experience for myself rather than rely on what teams of marketeers or academics would like me to believe.
This is what sets engineers apart from hair dressers or telephone sanitizers.
What's 40W? The W indicates that the oil as been tested in low temperatures (W=winter). It doesn't relate to the higher number.I know the manufacturers of oil publish a specification for their oil and I'm sure there are exacting tests to prove viscosity both hot and cold BUT in my years of experience of being an end user of their products I have found 0w/40 oils seem to be consumed by engines at a lot faster rate than 10W/40 oils.
If the higher 40W number is the same for both types of oil, anyone with an equiring mind would want to know why??? Something is not consistent with the tests springs to mind. Is the push for lower viscosity oils influenced by a need to demonstrate better fuel economy? Do the tests only have validity on a brand new engine which is up to specification? Do the tests take into account the long term effects that a thinner oil might have at high mileages? Do the manufacturers even care how much oil is consumed?
So, if genuine experience proves to me that my engine rattles less, burns less, maintains better pressure when hot and most importantly lasts longer then I have to say "B-gger the experts"
If I am unable to learn from experience then I will probably become extinct!
Call me a sceptic but I tend to believe what I see and experience for myself rather than rely on what teams of marketeers or academics would like me to believe.
This is what sets engineers apart from hair dressers or telephone sanitizers.
You have an interesting point of view for an engineer. Also speaking as a qualified mechanical engineer with 40 odd years of experience, I tend to believe what I see, experience and understand. Paul Daniels would love you in his audience.
Another key thing that is being missed in this debate is that viscosity is not the only, not even the most important, factor in film strength, which is the issue surely.
Thanks for that DSM2. I didn't want to get into a debate about oil - been there before and it is too irritating for words.
Of course film strength is the most important thing in a cylinder to piston face joint/gap and the higher the load the higher that needs to be to keep the metal parts apart! and too hot is bad news all round.
Paul Daniels is a magician and if anyone came up with a proven 100% solution that stopped all the 997 3.6's seizing/picking up - then I for one would not care if I understood why or not. You have to be pragmatic to be a good development engineer - accademics can ponder over why afterwards.
However in this case all the visual, technical, dynamic and practical evidence points to one cause and the trends with this model development point to the same cause and the changes Porsche have made since similarly point to the same problem as does every engineer who has tuned up an engine and had to change the coolant flow to stop similar problems.
Ironically - while I do repair an awful lot of these engines - I provide a warranty/plan that would minimise repair costs for the customer (not for me) if the worst happened and am also trying my best - by opening up this debate - to finding an inexpensive way to help owners avoid the problem altogether - so doing myself out of potential future work - but I just think it needs sorting out and is going to happen too much for comfort.
Unfortunately many owners prefer to live in a dream world and hope it will not happen or worry about the controversy harming residual values - but you will get a different perspective if you talk to someone who suffered and got no help from the manufacturer.
Baz
Of course film strength is the most important thing in a cylinder to piston face joint/gap and the higher the load the higher that needs to be to keep the metal parts apart! and too hot is bad news all round.
Paul Daniels is a magician and if anyone came up with a proven 100% solution that stopped all the 997 3.6's seizing/picking up - then I for one would not care if I understood why or not. You have to be pragmatic to be a good development engineer - accademics can ponder over why afterwards.
However in this case all the visual, technical, dynamic and practical evidence points to one cause and the trends with this model development point to the same cause and the changes Porsche have made since similarly point to the same problem as does every engineer who has tuned up an engine and had to change the coolant flow to stop similar problems.
Ironically - while I do repair an awful lot of these engines - I provide a warranty/plan that would minimise repair costs for the customer (not for me) if the worst happened and am also trying my best - by opening up this debate - to finding an inexpensive way to help owners avoid the problem altogether - so doing myself out of potential future work - but I just think it needs sorting out and is going to happen too much for comfort.
Unfortunately many owners prefer to live in a dream world and hope it will not happen or worry about the controversy harming residual values - but you will get a different perspective if you talk to someone who suffered and got no help from the manufacturer.
Baz
DSM2 said:
It isn't a theory. the oils are tested and have those viscosities at the set temperatures.
Perhaps your observations are more to do with the age of the oil?
I can honestly say that I have never had oil pressure or consumption issues with any car I have owned from new. Over about 35 years that is quite a number, petrol, diesel and various makes and milages up to and over 90K.
I put that down to sympathetic running in and careful warm ups.
My 911 takes 6 to 8 miles to get the oil up to 90c. It is really no hardship to take it easy for that period of time.
Having said this, I have seen test reports that indicate that Mobil 1, in any grade, is far from the best oil available in terms of film strength, which is what really matters.
Call it what you like fella, I know what I have seen and it had nothing to do with the age of the oil (although you are correct that the pressure does drop as any oil gets 'older' due the chains 'shearing', in fact it can be a reasonable guide as to when to change the oil). It isn't just an effect confined to my car either. I didn't have any particular issues per-se just that I noticed a difference with the 10w-40 oil.Perhaps your observations are more to do with the age of the oil?
I can honestly say that I have never had oil pressure or consumption issues with any car I have owned from new. Over about 35 years that is quite a number, petrol, diesel and various makes and milages up to and over 90K.
I put that down to sympathetic running in and careful warm ups.
My 911 takes 6 to 8 miles to get the oil up to 90c. It is really no hardship to take it easy for that period of time.
Having said this, I have seen test reports that indicate that Mobil 1, in any grade, is far from the best oil available in terms of film strength, which is what really matters.
I have nothing to gain by sharing my findings (I am not in the oil business) and I personally don't care what oil you use in your engine. I won't be using 0w-40 again though.....
ro_butler said:
bcnrml said:
They all need gentle treatment when cold. Ten minutes (as some continue to argue) is not long enough to warm up an engine in the UK's climate.
Amen to that!! The number of nice cars I have seen being thrashed to death coming out of Canary Wharf (presumably after being parked up all day) beggars belief Many don't care either as their cars are mainly under warranty!
Some, however, are just downright foolish!
Baz,
Thanks for the fascinating, if not slightly scary, information. I'm surprised you haven't had a job offer from Porsche germany for head of engine development!
As an owner of a 3.4 996 who's contemplating the next purchase (3.8 C2S or GT3 highest on list a moment), can someone summarise which engines are affected by this issue? I see Baz mentions "997 3.6's seizing/picking up"... so does that imply the issue doesn't happen (or is less common) on the 997 3.8 engine? Also what about the 3.6 GT3 engine?
Thanks for the fascinating, if not slightly scary, information. I'm surprised you haven't had a job offer from Porsche germany for head of engine development!
As an owner of a 3.4 996 who's contemplating the next purchase (3.8 C2S or GT3 highest on list a moment), can someone summarise which engines are affected by this issue? I see Baz mentions "997 3.6's seizing/picking up"... so does that imply the issue doesn't happen (or is less common) on the 997 3.8 engine? Also what about the 3.6 GT3 engine?
We get less 3.8's but the ones we do get have the same problem.
I am not sure how many 3.8's have been sold compared to 3.6's - and that may explain it?
Remember please on the scary front that it is vey very rare and very small quantities and if you had a Porsche warranty a replacement would cost you nothing or very little and if you had a Hartech Lifetime Maintenance Plan it would cost you less but you would have to pay for the parts only for a rebuild. But then with our scheme - your servicing is free (parts and labour) and your annual MOT and parts like clutches, brakes etc when you need them.
Baz
I am not sure how many 3.8's have been sold compared to 3.6's - and that may explain it?
Remember please on the scary front that it is vey very rare and very small quantities and if you had a Porsche warranty a replacement would cost you nothing or very little and if you had a Hartech Lifetime Maintenance Plan it would cost you less but you would have to pay for the parts only for a rebuild. But then with our scheme - your servicing is free (parts and labour) and your annual MOT and parts like clutches, brakes etc when you need them.
Baz
Some pictures on the subject
You will see a lot of pistons in various stages of decline from fully seized to just coating flaking off. Unfortunately we get through so many we have scrapped many previous ones and these are just what we have dealt with in the last few weeks.
You can see why just calling it scored bores is minimising the problem (for every scored bore there is a badly seized piston face), why calling it "picking up" is also minimising the level of damage, and that the cylinder damage is low down towards the hottest part of the cylinder (as the coolant depth is very shallow).
I HAD TO REDUCE THE SIZE AND QUALITY TO UPLOAD - SORRY i WILL TRY AGAIN WITH A DIFFERENT METHOD FOR CLARITY.
Baz
You will see a lot of pistons in various stages of decline from fully seized to just coating flaking off. Unfortunately we get through so many we have scrapped many previous ones and these are just what we have dealt with in the last few weeks.
You can see why just calling it scored bores is minimising the problem (for every scored bore there is a badly seized piston face), why calling it "picking up" is also minimising the level of damage, and that the cylinder damage is low down towards the hottest part of the cylinder (as the coolant depth is very shallow).
I HAD TO REDUCE THE SIZE AND QUALITY TO UPLOAD - SORRY i WILL TRY AGAIN WITH A DIFFERENT METHOD FOR CLARITY.
Baz
hartech said:
We get less 3.8's but the ones we do get have the same problem.
I am not sure how many 3.8's have been sold compared to 3.6's - and that may explain it?
Remember please on the scary front that it is vey very rare and very small quantities and if you had a Porsche warranty a replacement would cost you nothing or very little and if you had a Hartech Lifetime Maintenance Plan it would cost you less but you would have to pay for the parts only for a rebuild. But then with our scheme - your servicing is free (parts and labour) and your annual MOT and parts like clutches, brakes etc when you need them.
Baz
Am I correct in saying that the GT3 engine (Engine types M96/76/79/80) is a hybrid engine with water cooled-heads and upper cylinder sleeves with air-oil-cooled lower cylinder sleeves and crankcase with dry sump etc and based on GT-1 930 does not suffer this particular problem at all and that the GT2 and Turbo models (Engine types M96/70/70E/70S and 70SL) being a hybrid engine that has been designed from scratch with water-cooled heads and cylinder sleeves and an air-oil-cooled crankcase and dry sump and with cylinder sleeves cast from aluminium and inner surfaces coated with Nikasil not using the Lokasil (localised silicon) system only suffer from it in very small numbers.I am not sure how many 3.8's have been sold compared to 3.6's - and that may explain it?
Remember please on the scary front that it is vey very rare and very small quantities and if you had a Porsche warranty a replacement would cost you nothing or very little and if you had a Hartech Lifetime Maintenance Plan it would cost you less but you would have to pay for the parts only for a rebuild. But then with our scheme - your servicing is free (parts and labour) and your annual MOT and parts like clutches, brakes etc when you need them.
Baz
(I did not realise until recently that the GT3 engine is totally different to the GT2 and Turbo engine.)
hartech said:
We get less 3.8's but the ones we do get have the same problem.
I am not sure how many 3.8's have been sold compared to 3.6's - and that may explain it?
Remember please on the scary front that it is vey very rare and very small quantities and if you had a Porsche warranty a replacement would cost you nothing or very little and if you had a Hartech Lifetime Maintenance Plan it would cost you less but you would have to pay for the parts only for a rebuild. But then with our scheme - your servicing is free (parts and labour) and your annual MOT and parts like clutches, brakes etc when you need them.
Baz
Are you just talking about 997s? I don't know the stats but got the impression that around 80%+ of vanilla 997 Carreras were sold in the UK as 3.8 S models, making the 3.6 non-S model quite rare (ignoring all GT2/3/Turbo etc models). Interesting if you are seeing MORE 3.6 models - could suggest another dimension to this. I am not sure how many 3.8's have been sold compared to 3.6's - and that may explain it?
Remember please on the scary front that it is vey very rare and very small quantities and if you had a Porsche warranty a replacement would cost you nothing or very little and if you had a Hartech Lifetime Maintenance Plan it would cost you less but you would have to pay for the parts only for a rebuild. But then with our scheme - your servicing is free (parts and labour) and your annual MOT and parts like clutches, brakes etc when you need them.
Baz
Also, do you think this could be related to unsympathetic thrashing of these cars when they are cold?
You will see a lot of pistons in various stages of decline from fully seized to just coating flaking off. Unfortunately we get through so many we have scrapped many previous ones and these are just what we have dealt with in the last few weeks.
You can see why just calling it scored bores is minimising the problem (for every scored bore there is a badly seized piston face), why calling it "picking up" is also minimising the level of damage, and that the cylinder damage is low down towards the hottest part of the cylinder (as the coolant depth is very shallow).
Baz
what were the mileages?
Edited by nelly997s on Saturday 16th October 21:41
Pope said:
eagle1 said:
(I did not realise until recently that the GT3 engine is totally different to the GT2 and Turbo engine.)
It isn't, minus the two turbos and pipework the mechanicals of the above 3 vehicles engines are practically the same?Edited by Pope on Sunday 17th October 18:15
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