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Discussion Starter #1
Hi guys
Engine was opened this morning by BMW and I took this picture of the scratches on cylinder No4. The compression test is true to the scratches found on each cylinder wall, that is Cylinder 4 had the most scratches, then Cyl 3 etc etc Cylinder 8 and 5 were perfect with no scratches whatsoever.
What can cause this kind of scratches on the sleeves, car has 120 000km on the clock.








Cheers
 

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The obvious one would be the bits of crude seen in the picture between the wall and piston. If one or more of those lodged itself on a ring...
The fact that 1-4 are down and 5-8 seem great might suggest a leaky air filter at some point in the engines life on that side.
 

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I've posted this on other threads before, but it seems appropriate to place it here too. I was reading the following thread - Nowack Tuning Report, The Truth (Long Version) - from back in 2001, when a particular paragraph stood out and smacked me firmly across the cheek......

"Sometime during week three I was called by Nowack to be told that they had dismantled my engine to discover that the inside of the cylinders of my engine block were badly scratched. I was told that Nowack find that some 20-25% of the S62 engine blocks they see have this problem (other BMWM5. com users have been told the same thing). Apparently it is mostly to do with the way the engine is set up by BMW, although it was also suggested at one point that I had not run the engine in properly. That said, in a conversation with one of Nowack's engineers I was told that they have seen a new M5 with delivery mileage on it, which also has this problem. Apparently the cylinder scratching is not a disaster in the standard M5 -- it probably reduces power output a little, reduces engine life a little and, in the early life of the engine, might well lead to increased oil consumption. However, given that the real power gain comes from Nowack tuning the engine's ECU's to work the mechanics harder, the mechanics have to be optimal. Nowack cannot / will not tune an M5 with badly scratched cylinders. "
 

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Discussion Starter #5
I've posted this on other threads before, but it seems appropriate to place it here too. I was reading the following thread - Nowack Tuning Report, The Truth (Long Version) - from back in 2001, when a particular paragraph stood out and smacked me firmly across the cheek......

"Sometime during week three I was called by Nowack to be told that they had dismantled my engine to discover that the inside of the cylinders of my engine block were badly scratched. I was told that Nowack find that some 20-25% of the S62 engine blocks they see have this problem (other BMWM5. com users have been told the same thing). Apparently it is mostly to do with the way the engine is set up by BMW, although it was also suggested at one point that I had not run the engine in properly. That said, in a conversation with one of Nowack's engineers I was told that they have seen a new M5 with delivery mileage on it, which also has this problem. Apparently the cylinder scratching is not a disaster in the standard M5 -- it probably reduces power output a little, reduces engine life a little and, in the early life of the engine, might well lead to increased oil consumption. However, given that the real power gain comes from Nowack tuning the engine's ECU's to work the mechanics harder, the mechanics have to be optimal. Nowack cannot / will not tune an M5 with badly scratched cylinders. "
wow man, this guy had a raw deal but thanks for the information.

It was suggested that by the technician that dirt could cause this problem and my argument was exactly the same, common plenum, cylinder eight and four intake next to each other with cylinder eight still perfect.

I also had a question if this can be ring marks we see on the bore? I was assured that the rings rotate inside the groove and that it is unlikely to be the culprit ?
 

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Whilst there are 2 seperate air filters and intake pipes, the air they supply is mixed in the plenum, so they are not bank specific.


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True but air has a path even in an open space. I race sailboats and study air movement, that is what makes a sailboat go, that and beer. The plenum will have air flow. I think that there are two swirls of air under there with little or no mixing of the air from the two sources. Why do you think 1 and 5 are pointing backwards? My bet is that the passenger side of the engine is fed by the drivers side intake. I would suggest that 3 and 4 are the most likely to grab something with mass ie a piece of dirt. More likely because of pressure differences not because they are in a straighter path.The straighter path would also make them more likely to grab them do to momentum of the particle however.

I am certainly not claiming that it is the cause just a possibility. I do like what you posted better, but wonder why it would be more significant on 3 and 4?
 

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Coenraad,

here is my 2cents....

This is not soo bad scoring you got there....


Have seen way worse on engines that have way more compression than yours(that still made good power also),I am eager to bet this is not the culprint for your low results.

Was the compression test performed on a cold or warm engine?

Were the valve seats checked for leaks yet?

Have the bores a wash out at TDC?

What is the condition of the head gasket?

Is the cylinder head warped?

Very often,carbon build up in the combustion chamber,particles of for example chain covers(when the timing chain has too much slack,it eats into the covers),oil pump chain(eats also into the pump cover,was in my case the culprint for very light scoring on cylinder 1 and 5),...

It is very unlikely you lost such a huge amount of compression with that bit of scoring...


Before you go for anything regarding the bores,please confirm for sure that the other things I mentioned above are NOT the real issue!!!

I had a bit lower result on cylinder 3 and 4(about 8 BAR) with a blown up head gasket that melted between these two cylinders...

What is the history,did the car make strange engine noises,felt down on power,....
 

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I've seen the inside of quite a few alusil blocks - all with a similar pattern of light marking. I'd echo Raikkus comments ie it ain't necessarily a problem, although it always looks nicer if it's not there. Why have the heads been pulled?
 

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Discussion Starter #9
Was the compression test performed on a cold or warm engine?
First a cold test was done, then the result I posted was the warm engine results, the cold test readings were a bit higher on some of the cylinders than the readings of the warm engine

Were the valve seats checked for leaks yet?
The heads have not been checked yet

Have the bores a wash out at TDC?
What do you mean by wash out? I could see a definite mark at TDC where the rings stopped

What is the condition of the head gasket?
The head gaskets looked good, I could not see any problem or indication of leaks on the head gaskets

Is the cylinder head warped?
The heads have not been tested yet, I am awaiting the next action from BMW

Very often,carbon build up in the combustion chamber,particles of for example chain covers(when the timing chain has too much slack,it eats into the covers),oil pump chain(eats also into the pump cover,was in my case the culprint for very light scoring on cylinder 1 and 5),...
We have not yet taken the oil sump of but we could not see any damage to the chain guides

What is the history,did the car make strange engine noises,felt down on power,....
No strange noises, no loss of power.

I know I am very persistent in my quest to find out what happened and why my engine got damed and I appreciate any comments or suggestions. The reason why we took the heads of today was because we can not come to a conclusion without inspecting the engines inside? If you remember I had the low compression reading on the cylinder four last year, the reason for the current investigation.
 

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Discussion Starter #10
I've seen the inside of quite a few alusil blocks - all with a similar pattern of light marking. I'd echo Raikkus comments ie it ain't necessarily a problem, although it always looks nicer if it's not there. Why have the heads been pulled?
What would one consider as not too much marking? I agree that it would be nice not to see any scours marks in the sleeve, but like I said, and please this is my personal observation, the compression test reflects the scratch marks I could see in the sleeves? The two cylinder walls with no marks was the best and the cylinders with marks reflects the readings according to the marks observed in the sleeves. I took pictures of all the sleeves but the photos does not high lite the scratches nicely otherwise I would post them.
 

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I do not mean the brown marking you see on top of the wall,about 2 cm below that,do you feel that the wall has a dent inwards(washout)?

Please get them to check all cylinder head related stuff first!
 

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My perspective would very much depend on if this work was being done under warranty or not.
 
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