Valve Cover Shrinkage

jemdandyApril 8, 2007

Has anyone encountered shrinking valve covers? I did on my wife's '97 Saturn, with dual cams. The first indication was the oil fill cap jamming. It became very tight and resisted turning to the degree that one could not feel the quarter turn stops. It was really jammed. I did not knoew about this problem until it bacame very bad since my wife had been taking the car to an oil change parlor and I never got any feedback this was happening. Next, one spark plug began to fill will oil, and the cover leaked where it contacted the head. I discovered what had happened when I bought a new gasket set and installed it to stop the leaks. I bought a new oil fill cap also and the new cap was too tight in the hole. The valve cover was a plastic molding and it was shrinking.

The new gaskets cured the leakage around the sparkplug tubes but the cover did not seal well against the head at one corner. This is the corner without a bolt. To fix the oil fill cap, I removed the o-ring on the cap and sanded down its diameter until it would just fit into the hole, then cleaned it and put the o-ring back on.

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I am showing my age here-I was not aware that Saturn was using molded plastic for valve covers. I have owned cars with valve covers made from formed steel, and our Honda has a valve cover made of cast aluminum. I'm not surprised that a plastic valve cover would shrink and/or change shape over time. This part gets hot as a matter of course. I suppose that a plastic valve cover is less expensive to manufacture, but when you consider the environmental effect of the inevitable oil leaks, it hardly seems worth it. Is there an aftermarket valve cover for your car, made of steel?

    Bookmark   April 8, 2007 at 8:35PM
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That's strange. The valve cover on the '93 ford tempo my daughter drives is made out of something that feels like plastic. I don't think it shrank. It did start to leak last year which was a cause for concern to start with. Service manual said the gasket, a giant sized o-ring, wasn't replaceable. NAPA had an aftermarket metal reinforced cork gasket for it. It's worked fine so far.

Saturn must have been using some kind of funky material in your valve cover it it warped or shrank on you.

    Bookmark   April 9, 2007 at 8:06AM
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When you installed the new valve cover gasket, did you put a little dab of silicone on the headwhere the timing cover meets it? That is where you are probly seeing your leak. The oil will leak past the gasket at that seam. It is very common.

    Bookmark   April 15, 2007 at 7:25AM
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