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  #1  
Old 02-17-2007, 05:13 PM
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87 300D - Proactively Replace Timing Chain?

My question is whether I should proactively replace my timing chain on my 87 300D?

History....
- 287K miles but overall runs pretty good.
- At 90k - timing chain replaced due to failure ($$$$)
- $$$$ of work done to keep this running over last 10 years (rebuilt IP, wheel bearings, rebuilt A/C compressor, etc, etc, etc)
- Now trans shifts very rough for last year and slow fluid leak due to seal(verified vac pressure to trans, etc.)

So....I am thinking about getting a rebuilt transmission but am getting concerned that if timing chain goes....then it becomes doorstop.
I have read forums and it seems there is not a concensus on how often to replace chain and whether to replace all of the rails and everything else.

Any opinions on what I should do?

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1987 300D (277,000)
1995 E300 Diesel (122,000)
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Old 02-17-2007, 05:38 PM
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There is no age or mileage interval for replacing the chain. The factory recommended method for checking chain stretch or elongation requires checking timing marks at a given valve lift. A good enough indicator is to set the cam sprocket timing mark against the corresponding mark on the #1 cam bearing then see how far off TDC the crank pulley is. Take the average of several checks.

I don't know that there's a hard cut-off for the eyeball method but my guess is you're good up to 5* ATDC. Anything more and you should roll in a new chain. IIRC there are no offset keys for your engine.

I'm sure someone will chime in with other cut-offs.

You should probably check IP timing if you keep the chain. Using the RIV A-B light (available for rent through the tool forum) is the easiest way to go but there are eyeball methods as well.

Sixto
93 300SD 3.0
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Old 02-18-2007, 12:54 AM
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With 200K on it, I'd swap it. Make sure to get the proper tool to crimp the chain into place. Do the upper guide too.
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I'm not a doctor, but I'll have a look.

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Old 02-18-2007, 08:08 AM
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Thanks for the advice.

I would likely need to take this to a mechanic to get it done. Any idea of how much it might cost?

Also, I have looked thru the shopforum and am having a challenge finding diesel experts to do timing chaing(I already have good general mechanic but would rather someone more experienced do this work)? Any quick suggestions for Chicago/Milwaukee area?
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1987 300D (277,000)
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Old 02-18-2007, 09:44 AM
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I wouldn't worry too much about that first chain failing at 90k without knowing the exact reason for the failure. Very unlikely that it was the chain that failed that early. More likely something else took the chain out, resulting in the $$$$ repairs. The best advice (as Sixto sez) is to check the elongation and go from there.

Replacing the timing chain is not normally a "preventative maintenance" thing like replacing the timing belt on later vehicles.

Sorry I can't tell you how much it would cost to replace the chain.....

Wes
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  #6  
Old 02-18-2007, 09:57 AM
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I'll find out about the tchain for a 603 for ya. the prices might be slightly off for your area but you will get the idea for the hours it will take the "tech"
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Old 02-18-2007, 11:40 AM
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Quote:
Originally Posted by sixto View Post

I don't know that there's a hard cut-off for the eyeball method but my guess is you're good up to 5* ATDC. Anything more and you should roll in a new chain. IIRC there are no offset keys for your engine.
The limit for chain elongation is 4°. Anything more than 4° requires a chain replacement.

However, above 300K, there is some concern about the condition of the tensioning rail. There is a fair amount of work to remove it, but replacing the chain without looking at the rail is foolish on an engine with mileage above 300K.
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Old 02-18-2007, 01:19 PM
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There's nothing uniquely Diesel about a 603 chain so it'll be a cakewalk (what does that mean?) for anyone with experience rolling chains into MB V8s.

I've had 2 603s apart (3.5 with bent rods and 3.0 that replaced it) and what scares me about high miles is the condition of the oil pump chain tensioner. Both had deep grooves and missing chunks, albeit the missing chunks were not on the facing surface. In comparison the tensioner rail of both engines appeared to be in much better condition.

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93 300SD 3.0
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Old 02-18-2007, 01:23 PM
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I bought a new tensioner rail for my 617 when I had it apart without even looking at the old one. It requires a puller to remove it and I didn't have one but the tensioner slide rail was in such good shape, so close to new looking, that I didn't even bother with it. I did replace the upper chain guide because it was easy enough to do. That engine has 200K. Yours with much more might be a different story.
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  #10  
Old 02-18-2007, 06:19 PM
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10-12 hours for your job..

My area its 85$ an hour so in my place your looking at close to a grand in work time alone if everything goes by the book and the tech knows what he is doing.
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  #11  
Old 02-18-2007, 06:24 PM
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Just keep driving it. These are 1 to 3k$ cars, not worth any major repair. If it snaps the chain, which it won't, scrap it and find another for $1 to $3k. Chances are something else will take it off the road before the chain does.


240Joe

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