1995 XJS 4.0 L, 69000 miles. Checked my plugs today just for the fun of it, noticed the plug wells were full of oil. I replaced the cam cover gasket and boss seals a few months ago. What might I have done wrong when replacing the plug seals? I changed to full synthetic oil on my last change, would that have any impact? Any help/tips would be appreciated. Thanks

 

What presses against the seal to hold it in place? Is the cam cover the only pressing against the cam seal and spark plug seals?
The most likely cause would be improper torque (usually too much) of the cam cover bolts.

 

Took off the cam cover, bolts were way too tight, I must have used the old spec. Ordered New gaskets and such, will report back when I get the items installed to the correct torque. Thanks

 

Can I recommend the use of a gasket sealant when replacing those gaskets?

I had a similar problem and I used Permatex 85420, which is fuel resistant. Fixed me up right away.

It doesn't replace the gaskets, but helps it make a seal.

 

If you do it right that shouldn't be necessary at all, just makes a mess. You can use stuff like that sometimes to get a gasket to sit where you want to make installing it easier.

Garity said he over-tightened the bolts, so the gasket got squished out and didn't seal. I can't imagine they require much torque. It can differ with DOHC because the cover is so big, but most valve covers I have ever installed range from 5-10 ft/lbs

 

Even if done right, it may not be good enough. Magnesium coil cover couldn't guarantee a flat seal, so I went with the gasket dressing.

I chose the dressing to ensure a functioning seal.

 

What is the difference between the fuel resistant permatex and the form a gasket 2 permatex for this application? Thanks

 

Form a gasket is a black goopy substance that cures into a gasket. Would be a complete pain to remove, if you ever wanted to remove the gasket.

Gasket dressing is a thinner substance that leaves a sticky thin residue, filling any minor gaps between the gasket and what you're applying the gasket to. There's nothing to remove. I think if you were to swap out gaskets, you might not even have to reapply the dressing.

It's not expensive and readily available. I think it's a great tool to ensure a good seal.

 

check breathing pipes and hoses. Maybe high pressure in the engine