Timing chain cover gasket, 300E
 

Hi,

I am replacing my timing chain and have some questions after searching this forum. I was particularly intrigued by the inconclusiveness
of whether or not ro replace the chain at higher mileage.

Is there a gasket for the lower section of the timing chain cover on the 103 engines?

When replacing the timing chain what other miscellaneous parts, seals, gaskets, (cam sprocket, for example), etc are recommended?

The M103 engine has a ratcheting tensioner which makes the chain virtually trouble free. Conventional wisdom holds that these particular engines do not need the chain replaced for preventive maintenance purposes, only when the engine is apart for some other reason.

It sounds like you already have it apart, so here's the drill. To begin with, ensure that you remove the tensioner plunger by pushing it through, then feed it back through just enough to put it together. If you were to leave it in place you would probably break something when putting the new chain in place.

Once the new chain is in place, use the special sealer from MB for the upper front timing cover. This sealant is slick and allows you to start the shaft seal, then push the cover rearward without disturbing the bottom U seal. Gob the sealer in the bottom, rear corners. If you do this properly it will not leak, if you don't, it is guaranteed that it will leak.

Best of luck,

elkadi:

The lower timing cover does not use a gasket, rather the special MB black sealant to seal the timing cover to block surface.

I'm not sure where you saw the inconclusive argument regarding whether to replace your 103 chain or not, but the majority of advice and experience of techs and DIY'ers, including myself, is that the chain does not need to be replaced, if you've been changing your oil regularly.

The typical failure of these chains is due to breakage of the timing chain guide (plastic) and/or tensioner rail. Over time, these parts get very brittle and can fail. So, "while you're in there", whether or not you replace your chain or not, it would be very wise to replace the chain guide, and tensioner rail with the timing cover off.

Also, it wouldn't be a bad idea to replace the crankshaft seal on the timing cover, as it's only a $6 part, and easy to replace.

Larry's advice about the top timing cover is right on. If you "roll over" the top cover U-seal gasket, it will leak, so be careful.

Good luck!

Larry/Pmizell
Thanks for the advice. I should have clarified that I only had the upper timing cover off. Then I decided to take the cam sprocket off, which it slipped off with the chain still on. Then, to put it back I loosened the chain tensioner back, slipped the sprocket back in place (indexed to the cam) and drove the tensioner back towards the chain using the same number of revolutions. Is this OK??? I am not clear about replacing the chain tensioner by "pushing it through and then feeding it back through", especially when the old chain is still in place.
The chain seems just fine. The lower timing cover is in place except one of the top bolts is loose and allows about 1/8th inch of separation of the cover from the block. Is it OK to retighten it back or do I need to take the lower cover off (which requires taking off the harmonic balancer) in order to reseal the lower cover?
Thanks for all the help as the car has been down for three weeks or so and I look forward to it running again.

timing cover
 

Hi,

Just finished doing my top cover, used this site to figure out how.

Absolutely correct about the MB sealant, bought from this site. Made by locktite but could only find here, has a specific MB PART NUMBER.

If the bottom cover is loose, I am sure you would have lost seal and would need to remove, clean, and reseal surface to block. From what I've read on this site, the lower cover is no joke to remove, lots of stuff needs to come off.

I have 123000 miles and left the chain and associated hardware alone. I have other cars with chains and they run for ever over 180000 miles so far. Key is keeping clean oil and filter in car.

Joel

part number for sealant
 

Fastlane part number

Z9005-97595