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Oil on spark plug

14 years ago

My 1995 318is bmw started running rough and shutting off. I discovered that the number two spark plug hole and spark plug was covered with oil. I cleaned the hole and replaced the spark plugs with new ones. I also changed the air filter and gas filter. What is causing the oil to get into the spark plug area and how can I repair the problem? Please Help.

Thanks,

Bernie

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Comment (1)

jemdandy
14 years ago
I don't have details about your engine, but if it is like many other overhead cam engines, the spark plugs sit in deep wells in the valve cover. These wells are sealed with soft seals. When these leak, oil begins to fill the hole. There are a variety of causes for this leak:
1. Loose valve cover
2. Seal failure
3. Warpage or shrinkage of polymer covers.

If you valve cover is made of plastic, these often shrink or warp, even those made of glass filled plastic. A metal cover is more stable, but a metal cover can be malformed by over tightening, etc.

The usual fix is to install a new set of valve cover seals and inspect the condition of the cover and correct as needed. A new gasket set should have the main gasket for the perimeter of the cover plus a set of seals for the sparkplug wells. Read the installation instructions. A sealer may be required. If silicone rubber is needed, make sure that it is resistant to hot oil and rated compatible with the catalytic converter.

One sure sign of cover shrinkage: Has the oil fill cap started to bind? hard to turn and remove? (Molded cap that fits within a hole) One cause is shrinkage of the valve cover.
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Thank you all for your replies. I fixed the leak today by installing a new gasket set. When I took the old gaskets off, I found that the one around No. 1 sparkplug well had hardened and deteriorated, but the other were serviceable. It also had a weep along the front edge where the cover seats against the head. It's not leaking now, but the car hasn't been driven long enough for a true test. I found a possible contributor to this problem. When I tried to remove the oil filler cap, it was jammed. It had swelled to the point that to remove it required enough force to flex the valve cover a bit. Tomorrow, I'm getting a new filler cap. (Interesting what we find after the service contract runs out. This is my wife's car and her service contract expired this winter.)
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