Valve Cover Shrinkage
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.