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BMW 3-Series (E90 E92) Forum
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oily spark plugs but compression test is clean
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08-01-2020, 10:21 PM | #1 |
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oily spark plugs but compression test is clean
so I opened the car up to do some regular maintenance as you would on the n54 (compression testing, walnut blasting, serpentine belt replacement and oil cooler/housing gasket) and I notice all of my sparkplug threads are oily, especially cylinder 3 which even the coilpack is oily. I did the compression test thinking maybe I have a leaking and failing valve cover gasket and the test results are as follows:
cyl1- 190psi cyl2- 185psi cyl3- 185psi cyl4- 180psi cyl5- 175psi cyl6- 180psi anyone has an idea what is causing this oily sparkplug issue? thanks. |
08-01-2020, 10:25 PM | #2 |
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What does the valve cover gasket have to do with cylinder compression? But, yes, the oil you're mentioning is a sign of a failed VC gasket or a cracked VC.
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08-02-2020, 12:08 PM | #3 | |
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No idea why you did a compression test, |
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08-02-2020, 08:24 PM | #4 | |
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08-02-2020, 08:33 PM | #5 |
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08-02-2020, 09:34 PM | #6 |
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If the plugs were really burnt white and dry, I'd say they mean the engine is running lean
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08-02-2020, 09:50 PM | #8 |
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+1. Definitely VCG.
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08-03-2020, 01:29 AM | #9 |
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08-03-2020, 02:22 AM | #10 | |
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The compression test was done just to do a checkup. unrelated to the issue at hand. I did the compression test to see if there was a head gasket failure as the car has 222,000 km. I mistyped it in my first post. sorry. and for some reason I thought the two were related. |
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08-03-2020, 02:46 AM | #11 | |
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Hope the VCG fixes the oil issue, also a good idea to check for any cracks on the valve cover itself since your gonna do the gasket anyway. |
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08-03-2020, 10:23 AM | #12 |
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Yes, especially because OP observed a lot of oil on coil and spark plug on cyl 3 which is by the oil filler cap and where the VC cracks often on these.
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08-04-2020, 01:56 AM | #14 | |
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is it for sure a cracked VC? guess we cant tell till I open her up |
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08-14-2020, 11:45 PM | #15 |
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Did the valve cover gasket on mine as I had oil on every sparkplug...
Had horrible knock and misfire... Now it is all gone... (also replaced the VANOS solenoids and the crank position sensor since I was getting those errors as well) Look for oil leaks, are they coming from the VC or from under the VC? The VC is plastic on these cars so likes to crack... So far I am lucky and mine hasn't cracked... and I have over 170K miles. |
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08-15-2020, 01:00 PM | #16 | |
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It looks like the Gasket leaks more often than the Valve Cover itself cracking, but would budget for it at that kind of mileage just in case. |
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08-15-2020, 02:09 PM | #17 |
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Why would that make you sad? Valve cover is cheap and your motor is in good shape. What outcome were you hoping for? It’s possible it’s just your gasket but no way to tell without taking it off. OEM valve cover with bolts and gasket is under $400.
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