A neighbor has a 1987 420 SEL with a problem. She heard a tapping noise on start up and decided to drive her other car. She asked me to have a look which I just did. When I popped the hood I noticed a hole in the drivers side cam cover. Against my better judgement but out of curiosity I started it up. It started quickly and it did tap pretty good but it ran decent for the short time I ran it. I know something in the timing let loose BUT it runs too good for me to believe that it crunched the valves, in fact I've never seen one run after jumping time. I believe the chain is slapping making the noise and hole in the cam cover but it has not jumped time, yet. I have done nothing more than stated here. She said she's not going to fix it and has offered it to me very cheap. You think it would run so well, with excellent oil pressure during the 20 seconds that I ran it, if the timing jumped? I was thinking of buying it, replacing whatever broke [guide/rail/?], new chain, cam cover and driving it.

At idle, it would jump advanced , so wouldn't hurt a valve, sounds like a piece of guide came out (although I've never seen one fracture a valve cover, usually, thats the chain!!).
Other than a pissed off neighbor (once you are driving in her car, after fixing it), what do you have to lose?

Maybe the upper rail broke and somehow did not jump the chain, and then made the hole in the cover.

If there was damage to the valves, you would certainly know it. Sounds like a buy - with a new chain, tensioner, oil tube kits, upper rails and a new valve cover, you're in business.

Just don't start the car again until you find out what's going on.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Thanks guys! I know I've never seen one run with valve damage. I saw that hole in the cam cover and figured it was all over, having seen it before. I hated to even start it but I figured what the heck and to my amazement it cranked right up but it did rattle pretty good. That's all I've done so far, I haven't removed anything yet. She said she was going to sell it anyway and will not spend any more money on it. It's got over 200k on it but she's spent some money on it including a chain job at 125k, a trans at 180k and various other repairs including the A/C according to the records. I feel a bit guilty buying it for a couple hundred bucks [her offer to me] but I am

I'm off next week so I want to start tearing this apart to see exactly what's going on. I'm going to start with the valve covers to check things out. I hope it's upper guides/rails not anything to deep down requiring pulling the front of the engine off. Is there a link to a online repair manual for specifically the timing chain and components on this 420SEL ? I don't have any books and I'm looking for someting to go by. TIA

Please let us know how it goes. I just had the timing chain and guides replaced on my 90 420 SEL 170,000.

I would be absolutely amazed if you don't have a bent valve. You need to report your findings here.

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Auto Zentral Ltd.

Here it is nearly 2 months later and I have not yet torn into this. A broken wrist tends to limit your mechanical abilities I had a heck of a time finding this old post to get my ID and then try to remember my password but I'm back

I hope to get at this job very soon since my wrist has healed.

probably what happened here was that a piece of chain rail broke off and got between the chain sprocket and chain pushing chain against the valve cover and breaking it .i have seen this before 3 or 4 times in last 15yrs. i agree with previous posts,first you need to remove valve covers and check for any loose rockers which will indicate bent valves.

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David S Poole
European Performance
Dallas, TX
4696880422

"Fortune favors the prepared mind"
1987 Mercedes Benz 420SEL
1988 Mercedes Benz 300TE (With new evaporator)
2000 Mercedes Benz C280
http://www.w108.org/gallery/albums/A...1159.thumb.jpg

I agree. I got enthusiastic this am and was going to tear into it but I got sidetracked washing it then it just got too hot. I'd bet there's no damage to the valves whatsoever but that's just luck. It looks good that it sat there for 2 months anyway, my neighbor can only assume it was very extensive

Here's a photo of the old yacht after I cleaned her up this morning. It's still quite an impressive old classic

I thought I found it here but I can't seem to locate it now.

I'm looking for a guide [w/ photos would be great] on the step by step procedure on replacing the timing chain, tensioner and guide rails on my 420SEL.

Thanks in advance

I would just roll in a new chain and replace the top three guides. Probably a good idea to replace the tensioner too. To replace the guides you have to take the alternator bracket off and the power steering pump. Then you will see the pins that hold the guides in place. You can buy a tool to pull out the pins or you could try to make something.
If it runs good you could probably just get away with the one guide that broke and see how much the chain has streched.

I'm definately going to so the chain, tensioner and guide rails, as well as the oil tubes if necessary. There's no sense in not doing it right since it's opened up already.

I remember the process I read mentioned everything you have but I'd like to find that link again. It was a very detailed step by step guide and had photos showing the different steps but I still can't seem to find it.

http://www.peachparts.com/Wikka/M117TimingChain


Could this be what you are looking for. Check out the DIY forum

YES! That's it.

There was another one that got into the guide rails too but I can't find this stuff now.

I'm searching for the best source for parts too so I can get them ordered. Some confusion on exactly what upper guide rails I need.