problem identified - PeachParts Mercedes-Benz Forum

dtrain · #1 07-12-2002, 04:46 PM

I posted a thread several weeks ago concerning my '89 420 SEL having a rough idle at when I started the vehicle. I checked several avenues that were suggested and nothing turned up until I started the car yesterday and it wouldn't turn over.

I had a mechanic take a look at it and he determined that the timing chain tensioner had broken. He also said that the timing chain was on its way out and at least two of the plastic guides were broken.

He claimed that the links were jumping when the car was idling upon ignition and that as the rpms rose, the "roughness" would disappear because this could not be detected at higher rpms.

Does this sound legitimate? I am supposed to see the car tomorrow morning. His price tag for fixing this is around $1,600.

If this is indeed the problem, is that a fair price for fixing it and could this be a diy job for a fairly amateur mechanic?

G-Benz · #2 07-12-2002, 05:18 PM

There are tons of threads regarding forum members who rolled in their own timing chains.

I'm not looking forward to doing one, but probably will when the dreaded head gasket finally gives out.

Some special tools are required such as the crimp used to fasten the link onto the new chain, but I believe the most difficult part of the job is patience.

Go too fast or get careless, and you will wind up having to dismantle more of the engine than you care to...

dpetryk · #3 07-12-2002, 07:36 PM

Ive done three of them. Do big deal. It does take te right tools and a small amount of above average DIY skill. The mechanics story sounds fishey to me. Normally when the rails break the chain jumps and you have bent valves. If they are broken and it didnt jump timing, then there are some loose pieces running around inside your engine. All of he chains I have done used clips so no need for the crimping tool.

Quote:

He claimed that the links were jumping when the car was idling upon ignition and that as the rpms rose, the "roughness" would disappear because this could not be detected at higher rpms

Sounds bogis to me. If links were jumping around, you would have bent valves.

While I was in there I replaced the valve stem seals and my oil consumption went to zero on both of my 420's. Total cost about $150 and about 6 hours time.

suginami · #4 07-12-2002, 07:38 PM

I agree that the diagnosis sounds wrong.

Having said that, if you have the original timing chain, tensioner, and guide rails in your '89 420 SEL, I don't think you'll find a person on this site that wouldn't recommend replacing them.

Do a search on 'timing chain' and you can read these threads all day and night.