Timing cover seal problems M104 E320 - PeachParts Mercedes-Benz Forum

tgmiller77 · #1 03-22-2008, 03:08 PM

I had what I thought to be a bad oil leak from the upper timing cover. Water pump and the radiator needed to be replaced, so I decided to reseal the upper timing cover. Used MB sealant and new gaskets and new valve cover gasket (I can't imagine screwing up the valve cover gaskets).
Resealed it 2 times, still leaking a little at the front behind the corner of the cover and bad at the back if the engine. I have read all the threads on this issue and made sure to do it right.
Has anyone else had so much trouble with sealing the timing cover. Is it time for a head gasket? If it the head gasket is to blame for the cover not sealing I will let an indy do it for the sake of my mental stability. Any help on this issue would be great.
Thanks, Greg.

Kestas · #2 03-22-2008, 05:51 PM

Where is it leaking at the back of the engine?... from the valve cover or the head deck? If it's not leaking from the valve cover then it's time for a new head gasket.

Since you've read through the old posts I assume you knew not to add RTV to the seal itself when doing this job.

tgmiller77 · #3 03-22-2008, 07:58 PM

No, I did not add the RTV to the gasket except on the ends where it meets the head. It seems to be leaking where the head gasket, head and the cover meet. I was very careful in that spot to get it right, but oil is finding its way out. Extremely frustrating!!!
In the back I need to get it up on ramps and take a better look. The two half moon gaskets in the back could be leaking but it feels dry back there. I did add a little RTV where it meets the gasket.

Ferdman · #4 03-23-2008, 03:22 AM

Greg, it's best to use the black MB sealant when replacing the upper timing chain cover ... just a dab in the recesses at the ends of the horseshoe gasket. Reinstalling the valve cover without knocking the half-moon sections of the gasket out of place is tricky. It's best to use an inspection mirror to ensure the gasket and valve cover are seated properly. Hopefully the head gasket is not shot. The head gasket on our daughter's 1991 300CE is shot (confirmed by a local independent tech who charges $1,500 to replace) and it leaks oil badly ... small puddle of oil quickly appears when she parks. That's a job I'm apprehensive about, but it will be a wonderful learning experience.

tgmiller77 · #5 03-23-2008, 11:23 AM

Do you add any sealant to the half moon gaskets? The old ones had a little at the ends. I put a little on the half moons because that was the way the old one was. If it needs to go on dry let me know.
The front seal would be OK to leak a little when the car is parked, but leaking while the car is running worries me.
On the U-gasket, I placed a dab at the ends and ran a small bead the the corners where everything meets. Is that not enough to get this thing to seal properly?

Ferdman · #6 03-23-2008, 11:50 AM

Greg, for the upper timing chain cover use a dab of MB sealant in each recess at the ends of the horseshoe gasket and a light coat of sealant on the mating surface of the timing chain cover to the head. It's important to carefully clean off all old sealant from the upper timing chain cover before reinstalling it ... making sure not to gouge/score the sealing surface. After I replaced the upper timing chain cover gasket there was no oil leakage.

No need for any sealant on the rubber valve cover gasket. Make sure the valve cover gasket is soft and pliable. If it's dried out or exhibiting cracks it would be a good idea to replace it.

tgmiller77 · #7 03-26-2008, 09:39 AM

Ok. I am a little confused. After the mating surfaces have been cleaned, do you only put a dab of sealant in the corner recess and not on the gasket itself? I put the dab on both the end of the gasket and the corner recess. Maybe I used too much sealant.

Kestas · #8 03-26-2008, 12:02 PM

That should be okay. The excess will squeeze out and hopefully won't be a problem.

I'm guessing that there's some movement of the horseshoe seal surface during thermal cycling, and that's why adding sealant to the bulk of the surface would make matters worse. When I did mine, I lubed the horseshoe seal surface with a light coating of silicone grease to ease assembly. I also practised with a couple of dry runs so I didn't have to fight time once sealant was applied.

Ferdman · #9 03-26-2008, 03:42 PM

Greg, a dab of sealant goes in each recess at the end of the horseshoe gasket ... no sealant on the gasket itself. A thin coating of sealant is needed on the vertical surface of the upper timing chain cover that mates to the head.

tgmiller77 · #10 03-27-2008, 10:36 AM

I understand now. Maybe the third time will be the charm. I was putting a bead in the corner and a dab on the gasket itself and it is probably leaking through the recess, because it leaks behind the sealant.
I still have to take the valve cover off and inspect the gasket to see if the rear engine leak is the gasket was installed incorrectly.
Thanks for the tips.
Greg

tgmiller77 · #11 03-29-2008, 07:30 PM

Well I guess miracles do happen. I took the valve cover off after letting the car sit for a week. The back part of the gasket had come out on assembly and was not seated properly. Well I started the car up and no leak. The front cover did not even leak!!!! I guess I did not let the sealant cure long enough before testing. I did give it almost 24 hours but I guess it was not warm enough for a good cure. Thanks again for the help.

Ferdman · #12 03-30-2008, 09:54 PM

Greg, glad to hear that your oil valve cover gasket and upper timing chain cover gasket are sealing properly. It's satisfying to successfully complete a DIY job.