1 of 6 pistons without carbon buildup

LeMans335d · 12-23-2022, 10:15 PM

Hello all,
I have a 2011 335d with 92k miles that I bought with 82k miles 2 years ago. The car is completely stock but in need of maintenance. I'm doing CBU cleaning on my car along with several other maintenance items and just out of curiosity I decided to take a look down the injector holes to see the condition of the pistons. Five of the pistons had minor carbon buildup, as I expected, but cylinder number five was spotless, it looks brand new. There was extreme carbon buildup in all the intake runners to all six cylinders. The only time I've encountered this before is with a blown head gasket but everything I read says it's nearly impossible to blow a head gasket on this engine. Plus, the car has been driving well, never overheated, no codes, no white smoke, no idle issues, no milky oil or coolant. No signs of a blown head gasket. Any ideas what else it could be? I will pressure test the cooling system when I put the car back together but if there is something else I should look at while the car is apart I'd like to go ahead and do it.

mifesto · 12-29-2022, 10:45 AM

why are you looking for a problem? it doesnt burn coolant, no smoke, no oil/coolant mixing.. and coolant system passed your pressure test. its typical in many cars, the carbon buildup happens in the back cylinders then front. leave it be.

LeMans335d · 12-29-2022, 10:51 AM

Quote:

Originally Posted by mifesto

why are you looking for a problem? it doesnt burn coolant, no smoke, no oil/coolant mixing.. and coolant system passed your pressure test. its typical in many cars, the carbon buildup happens in the back cylinders then front. leave it be.

I'm not looking for a problem but I'm not willing to ignore the signs of something out of character. If 5 pistons have carbon buildup and one looks brand new at 92k miles something isn't right. I haven't done a pressure test yet, I'm planning to do that after I get everything back together.

mifesto · 12-29-2022, 08:48 PM

ive seen some vids w blown headgasket where you pressurize the system and you can see a trickle of liquid running down cylinder wall with probe or at minimum water drops on pistons. gluck

lnxguy · 01-03-2023, 10:03 AM

Searching for a problem that isn't there?

12-23-2022, 10:15 PM	#1
LeMans335d Registered 0 Rep 3 Posts Drives: 335d Join Date: Dec 2022 Location: Arizona iTrader: (0)	1 of 6 pistons without carbon buildup Hello all, I have a 2011 335d with 92k miles that I bought with 82k miles 2 years ago. The car is completely stock but in need of maintenance. I'm doing CBU cleaning on my car along with several other maintenance items and just out of curiosity I decided to take a look down the injector holes to see the condition of the pistons. Five of the pistons had minor carbon buildup, as I expected, but cylinder number five was spotless, it looks brand new. There was extreme carbon buildup in all the intake runners to all six cylinders. The only time I've encountered this before is with a blown head gasket but everything I read says it's nearly impossible to blow a head gasket on this engine. Plus, the car has been driving well, never overheated, no codes, no white smoke, no idle issues, no milky oil or coolant. No signs of a blown head gasket. Any ideas what else it could be? I will pressure test the cooling system when I put the car back together but if there is something else I should look at while the car is apart I'd like to go ahead and do it.
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12-29-2022, 10:45 AM	#2
mifesto Private First Class 26 Rep 141 Posts Drives: 2008 335xi Join Date: Aug 2016 Location: nj iTrader: (1)	why are you looking for a problem? it doesnt burn coolant, no smoke, no oil/coolant mixing.. and coolant system passed your pressure test. its typical in many cars, the carbon buildup happens in the back cylinders then front. leave it be.
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12-29-2022, 08:48 PM	#4
mifesto Private First Class 26 Rep 141 Posts Drives: 2008 335xi Join Date: Aug 2016 Location: nj iTrader: (1)	ive seen some vids w blown headgasket where you pressurize the system and you can see a trickle of liquid running down cylinder wall with probe or at minimum water drops on pistons. gluck
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01-03-2023, 10:03 AM	#5
lnxguy Lieutenant Colonel 354 Rep 1,721 Posts Drives: 2009 335D Join Date: Jun 2016 Location: Barrie iTrader: (1)	Searching for a problem that isn't there? __________________ '09 335D
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