400E Wet spark plugs

[_BenzW124]

Hi guys. I'm new to the forum and sorry if I'm reposting something discussed before.

I was in the process to change the spark plugs on my 1994 E420. I removed spark plugs 6 and 8 since they're easier to get to, and both are wet on the threads as seen in the pictures. There seems to be oil ONLY on the inside threads of the spark plugs. My car doesn't burn or consume any oil as far as I've checked before. Spark plug 6 well had oil in it, however spark plug 8 well did not seem to.

Where do you think the oil is coming from? Your help is very appreciated.

I did not replace the spark plugs since I came across this issue.

 

[JC220]

Hi guys. I'm new to the forum and sorry if I'm reposting something discussed before.

I was in the process to change the spark plugs on my 1994 E420. I removed spark plugs 6 and 8 since they're easier to get to, and both are wet on the threads as seen in the pictures. There seems to be oil ONLY on the inside threads of the spark plugs. My car doesn't burn or consume any oil as far as I've checked before. Spark plug 6 well had oil in it, however spark plug 8 well did not seem to.

Where do you think the oil is coming from? Your help is very appreciated.

I did not replace the spark plugs since I came across this issue.
View attachment 129105View attachment 129106View attachment 129107View attachment 129108

There are large rubber seal rings between the cylinder head and valve cover at each plug well. I suspect your valve cover seals are therefore leaking and require replacement.

Spark plugs from MBs of this era generally do come out pretty carbon covered and filthy anyway nothing to be overly concerned about but raw oil from valve cover seals needs fixing obviously.

 

[gsxr]

Ditto what JC220 said above. Replace the valve cover gaskets, and pray no prior mechanic applied sealant to either side of the rubber gaskets, or you'll spend HOURS scraping it all off. Buy OE/Genuine gaskets, they don't cost much more than aftermarket.

Otherwise your plugs look normal. Gap new F8DC4 non-resistor plugs to 1.0mm, normal change interval is 30kmi.

 

[nocfn]

You will also need metric swivel hex (male) sockets to remove valve cover to replace the "seal". Do some searches here on some "how to" cam oiler tubes. As you might expect, doing work proactively is wise, so get ready for some while you are there stuff: Upper chain guides, cam oil tube swap to aluminum w/Orings, Oil separator. If your breather hoses are hard, vacuum lines and connections... cam seals, insulators, caps, rotors, coils. It goes on and on then suddenly you are finished, until you find out you are not. Welcome, by the way!