420 SEL timing chain help!!! - PeachParts Mercedes-Benz Forum

420SEL Jake · #1 09-01-2008, 08:36 PM

Guys i need some help. I was driving on the highway when I lost all power and I pulled over and I noticed that there was a large crack in my drivers valve cover. The car's vacuum gauge went through the roof and then I notice the car was not running. The timing chain still spins if i try to start it but looks like there is a slight bump in it while it turns but might be an illusion. There was slight scoring at the top of the valve cover.
Would a broken valve cover stop the car from starting and would could have broken the valve cover?
I noticed that the timing chain seamed to slap a bit after I sat in hot traffic for 20 min... see the picts.

420SEL Jake · #2 09-01-2008, 08:40 PM

Here is a pict from the piece I broke off. Oh the valve cover was super brittle
see the scoring

wbain5280 · #3 09-01-2008, 08:47 PM

This is a common problem with old brittle chain guides and chain wear. You will have to remove the head, replace the bent valves, put in Helicoils or Timeserts into the head bolt holes.

You can also find a replacement engine.

Where are you located?

Lexxani · #4 09-01-2008, 08:47 PM

Im thinking possible chain tensioner failure, mabye a broken chain guide, the ones in your engine are plastic.

Lexxani · #5 09-01-2008, 08:50 PM

beat me to it Warren.

420SEL Jake · #6 09-01-2008, 09:15 PM

There is a MB junk yard 10 miles from me in Ottawa and I have sunk a lot in to upgraded parts and killer wheels. I might buy another 420 SEL or 560 SEL and do a parts swap. If I get a new block then I am going to redo all the seals and what not. I figured that it was the guides or tensioner, I was warned by a mechanic this could happen. Any advice on changing a timing chain LOL?

Strife · #7 09-02-2008, 12:21 AM

Sorry to hear about this.

How many miles were on it when this happened?

There is a lot of help on this board forn this subject (unfortunately, in this case, this would be equivalent to closing the barn door after the horses ran out). It isn't a difficult job but you really need the shop manual and having the right tools helps (although the job is not impossible with improvised tools).

It's very likely that you bent some valves. That it happened at speed (and not at start-up) might make even more serious problems (broken cam, damaged pistons) possible. If your car is really nice, I'd get a donor engine, fix that up with new timing chain and associated parts, and put it in.

420SEL Jake · #8 09-02-2008, 12:26 AM

I had 200,000 miles on and i am the second owner but put 34,000 miles on it last year. I love this car and am currently as we speak looking for another... Gas or Diesel w126. I put a lot of love into it and replaced shocks, headlamps, breaks, HID kit, new bumpers and great 500 SL rims. If you hear of anyone selling a car here in N.America let me know.

wbain5280 · #9 09-02-2008, 04:36 AM

You haven't damaged the bottom end, just the drivers side valves are bent and the pistons have some scratches on them. You can repair it but an engine swap would be easier.

I did a write up on my 420SEL with pics for chain guide and chain replacement which you will do if you get a replacement engine.

http://www.peachparts.com/shopforum/showthread.php?t=185820

More on your engine damage:

http://www.import-car.com/ic/ic40024.htm