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Old 09-14-2003, 09:39 PM
jsmith's Avatar
Join Date: Aug 2001
Location: At Sea
Posts: 1,729
m104 - oil in sparkplug well

i changed my sparkplugs today and found that plug# 6 all the way in the back had oil in the plug well. i could see that it was leaking at the valve cover gasket. having no other options i snugged down the nuts that held the valve cover down at that end. i don't really think that would do the trick so i think i will need to replace the gasket at some point. is there a procedure outlined in the manual on how to install the gasket and tighten the nuts?

my other question to this is whether this could be in some way related to my misfiring problems that i have had a couple of times in the past when i had not used the car for about a week. once cylinder would not fire right away but would eventually do so after a few seconds. i ascribed that to a collapsing lifter but since it has now happened only 3 times (all after sitting for a week), i wonder if it was just the coil's plug boot getting soaked in the oil. that boot was replaced as i had taken this opportunity to replace all the coil plug boots and it seemed to start and run better over all.
1993 300e-2.8
- gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"
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Old 09-14-2003, 11:30 PM
Registered User
Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Get a new gasket, they aren't expensive.

Remove valve cover (and I cannot help much here, I don't remember what an M104 valve cover looks like!). If there are holes in it for the spark plugs on top, there will be gaskets for those as well, like on the old M110 engine. Probably four or six 10 mm bolts, maybe 8 if it is similar to the M103. The plug wires are in a plastic tray -- on the M103 you can pull the tray off and leave the wires in it. Don't know on the M104.

Remove all old gaskets -- they fit over the edge -- and make sure the cover is clean where the gasket fits. Wipe the head where the gasket will do down with some solvent -- it must be clean and dry, no oil or dirt.

Fit gasket to cover, no sealant. It should stay in place if pressed on.

Fit cover back onto the engine. Make sure the gasket is still in place with no sections rolled under anywhere. Lift cover and thump down onto the head firmly, repeating until it goes "CLOP" instead of "THUMP". This ensures that the gasket is seated all round. You'll hear the difference. Re-install the bolts and tighten with your hand around the head of the ratchet, not on the handle. That way you won't overtighten.

I'd think the oil wouldn't make much difference on the spark unless the boot were bad already, but if it's been there a long time, it may cause the rubber to deteriorate.

1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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