1988 300E Valve Cover Gasket Replacement - PeachParts Mercedes-Benz Forum

JimSmith · #1 04-17-2003, 10:37 AM

Hi,

My 1988 300E has developed some steady weeping of oil past the valve cover gasket, and I plan to replace it shortly. I have read some accounts of this being a somewhat less than straightforward gasket replacement job. If anyone has a few hints to make it go easier, please pass them on. Thanks, Jim

Duke2.6 · #2 04-17-2003, 12:15 PM

I did this job on my 2.6 a few years ago. I don't recall it being anything other than completely straight forward. The cover comes off without removing anything other than the PCV hose and the igntion wire harness. I have a Snap-on tool for removing the plugs wires from the plugs. Keeping all the wires straight in the channel can be a little tedious. I recall that I just removed the harness channel from the cover, and moved it out of the way, but it might actually be easier to remove the cap and then remove the cover with the harness assembly and cap attached. Clean the gasket channel throughly before installing the new gasket.

Wipe down the head mating surface and bottom of the gasket with silicone spray. This will keep the gasket from seizing to the head, so if you have to pull the cover in the future, the gasket won't be damaged, which will allow you to install the cover with the old gasket with a good chance of not leaking.

Don't recall the torque spec off hand, but I think it's in the range of about 90-100 in-lbs. Do it evenly in a couple of increments.

Duke

JimSmith · #3 04-17-2003, 03:32 PM

Thanks,

I will be on my way to get the gasket shortly and will let you know how it went this weekend. Jim

MTI · #4 04-17-2003, 08:02 PM

A good thing to keep in mind about the valve covers on hydraulic valve engines, is that since the valve clearances aren't adjusted as part of routine maintenance, it's still a good idea to inspect and replace the gasket, maybe every other year just as preventive maintenance and keep the engine bay cleaner.

John Plut · #5 04-17-2003, 09:51 PM

While you have the valve cover off you might consider painting it. I have painted a couple and it really dresses up the engine. Gloss black Rustoleum spray enamel works well. Be sure to sand or strip off the old peeling paint first.

Duke2.6 · #6 04-17-2003, 11:50 PM

My theory is: "If it works, don't fix it." The OEM molded rubber cam cover gasket is very good quality and should last a loooooong time. I don't see any need to peridoically replace it. I believe the reason mine started leaking was that is wasn't replaced when the head was removed for warranty work.

One thing that might be worthwhile is a check of the bolt torque after a few heat cycles, and, of course, you should use anti-seize compound on the threads.

The cover is coated with a thick polymer that provides acoustical attenuation of valvetrain noise. Over time the coating will blister and peel. Painting won't restore the cover's OEM appearance which is satin black, so the only way to keep it original looking is probably to buy a new one.

Duke

Duke

JimSmith · #7 04-19-2003, 02:42 PM

Duke 2.6 and others,

Well the deed is almost done. First I washed the engine with some Gunk engine cleaner and then rinsed it clean at the local do it yourself car wash. Then I drove it home and squirted the fasteners with penetrant and let it sit for a while, until the parts were not too hot to touch. The fasteners came out without much trouble except the one on the front passenger side corner of the engine. This one was hard to turn out, and needed the wrench attached up to the last turn. The old gasket broke in two pieces when I got the cover off, and it seems the previous owner had someone use a little form-a-gasket like material on the semi-circular cut-out at the rear.

The cover was pretty nasty, meaning dirty with lots of brown stuff on the inside surfaces. I washed it with gas a couple of times, then scrubbed it with a toothbrush and rinsed it with gas a few more times. There is a chip in the coating along the gasket seating edge along the rear of the cover, which I sanded to make the transition smooth. Then I rinsed it a few more times with gas, but the staining on the inside kept coming off ever so slightly on my clean rags. I let it dry for half an hour in the sun, and got ready to reassemble.

I used some synthetic assembly grease rated for high temperatures to seat the gasket on the cover and the cylinder head, then put it in place and reconnected the two hoses. I had my 15 year old son help put the fasteners back in, and we slowly tightened them from center to the ends.

We set the torque wrench to 15 Newton-meters, and slowly drew the fasteners up tight, when, the last fastener on the passenger side front corner broke when we gave it its final increment. We took the cover back off, and the fastener stub came loose by giving it a little whack with a punch. I unscrewed it by hand. We then re-cleaned and reassembled the cover to the head, this time using 10 Newton-meters. I took one of the fasteners from the center span and put it back in the front passenger side hole, but now cannot drive the car until I get a new fastener. I will buy 8 new ones though since I am sure they have been over torqued.

Well, thanks for the encouragement and helpful hints. Too bad it is Saturday and I cannot get a screw until Monday, at the earliest. Thanks again, Jim