Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Diesel Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 11-09-2013, 01:04 PM
Registered User
 
Join Date: Aug 2013
Location: Los Angeles area
Posts: 607
Timing Chain Stretch results

Cooljjay convinced me to check the stretch before replacing the chain outright, which was a good idea. Now that I've done it, I'm confused about the options, specifically the offset keys available. The FSM says one thing, details from the sellers of the keys say another.

Which one do I get?

I measured the timing chain stretch as per the procedure in the FSM. Dial Indicator, set to negative .08 and then advanced the crank slowly till it was as 0, took my reading on the crank and to my eye its right between 10 and 15. Pics attached show it, one with the marks clean and one dirty. I repeated this 3 times, and got the same result.

Now for the confusion. The FSM says a new chain would be at 9 degrees. And 11 degrees after about 20,000 KM.

In the FSM there are these woodruff keys mentioned:
  • Part # 621 991 04 67, Offset 0.7 mm, For correction of about 4 degrees.
  • Part # 621 991 02 67, Offset 0.9 mm, For correction of about 6.5 degrees. (this same part number on Pelican says 3 degrees).
  • Part # 621 991 01 67, Offset 1.1 mm, For correction of about 8 degrees.
  • Part # 621 991 00 67, Offset 1.3 mm, For correction of about 10 degrees.

However, when one goes to look at Pelican or ********AZ or anywhere else these keys with the same part numbers have a completely different value given for degrees of correction. On all these sites they only show 3 keys now, and the correct for 2, 3 and 5 degrees. The same part number 621 991 02 67 shows a correction of 3 degrees on everything I can find. Am I right to be confused?

Attached Thumbnails
Timing Chain Stretch results-sam_0138.jpg   Timing Chain Stretch results-sam_0134.jpg  
Reply With Quote
  #2  
Old 11-09-2013, 01:29 PM
whunter's Avatar
Moderator
 
Join Date: Dec 2003
Location: Metro Detroit, Michigan
Posts: 17,362
FYI

To answer your questions.

There are only three available, all others have been eliminated more than fifteen years ago.

As you may have gathered from my other post on this topic:
* It is a waste of time/money to use offset keys.
* A key does not correct over all timing, at best it is a partial bandage.
* The hours required to check chain elongation = you could have already rolled in a new timing chain = pulled all components back into timing alignment.

.
__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1980 240D
1983 300D
1984 190D
Reply With Quote
  #3  
Old 11-09-2013, 01:33 PM
Registered User
 
Join Date: Dec 2009
Location: Northwest Ohio
Posts: 605
I think the discrepancy relates to the fact that the crank turns twice for every one turn of the camshaft.

So the FSM is referring to degrees at the camshaft and the parts suppliers are referring to the degrees at the crank, which is where people measure stretch. The FSM values are twice the parts suppliers'.

The key you need is the difference between the reading and 11 ATDC. It looks like you have about 2 degrees of stretch.
__________________
1981 300TD 310k miles
1970 280sel 172k miles
1966 230 Fintail 162k miles

"Where are we going? And why am I in this hand basket?"
Reply With Quote
  #4  
Old 11-09-2013, 01:33 PM
NC-Diesel's Avatar
Registered User
 
Join Date: Jul 2012
Location: Chapel Hill, NC
Posts: 402
Gotta agree with W on this one. From a time and $$ efficiency standpoint just replacing the chain is the best option if you have access to a crimper.
__________________
1978 Mercedes 240D
1981 Mercedes 240D
1982 Mercedes 240D
Reply With Quote
  #5  
Old 11-09-2013, 01:48 PM
Registered User
 
Join Date: Aug 2013
Location: Los Angeles area
Posts: 607
Quote:
Originally Posted by NC-Diesel View Post
Gotta agree with W on this one. From a time and $$ efficiency standpoint just replacing the chain is the best option if you have access to a crimper.

And that is the big IF, the crimper really keeps this out of the hands of the DIYer.
Reply With Quote
  #6  
Old 11-09-2013, 01:50 PM
Registered User
 
Join Date: Dec 2009
Location: Northwest Ohio
Posts: 605
I have to say that I've been running for a couple of years with a 4 degree offset that corrected for my stretch.

With 300k miles on the engine, I recently decided to roll-in a new chain (with a 0 degree offset key). The car runs MUCH better. The only difference I can figure is that it corrected the IP timing, which is uncorrected by a camshaft key.

While I had not checked the timing of the pump before installing the chain, when I drip-tested it right after, it was dead on 24 degrees. Perfect.

One other thing an offset key will not help is wear on the sprockets from a stretched chain.
__________________
1981 300TD 310k miles
1970 280sel 172k miles
1966 230 Fintail 162k miles

"Where are we going? And why am I in this hand basket?"
Reply With Quote
  #7  
Old 11-09-2013, 01:51 PM
Registered User
 
Join Date: Aug 2013
Location: Los Angeles area
Posts: 607
I'm starting to think just leave it, I'm 3.5 degrees off, it's still well within the 7 degrees where the FSM says to replace the chain. Granted it'd be easier to do now (if I had access to the crimper) but, it doesn't seem that much more difficult when the engine is in the car, and I should get 50,000 more miles as it is. Given this won't be a daily driver, that's about 8 years for me.
Reply With Quote
  #8  
Old 11-09-2013, 02:00 PM
Registered User
 
Join Date: Dec 2009
Location: Northwest Ohio
Posts: 605
Just saw the post on the crimper. I did not use one.

As has been discussed over the years on the forums, I "peened" the link ends. Actually, I had a chain breaker that I used to round over the ends. It's not rocket science, but if anyone has qualms about it I wouldn't advise doing it without the crimper.

__________________
1981 300TD 310k miles
1970 280sel 172k miles
1966 230 Fintail 162k miles

"Where are we going? And why am I in this hand basket?"
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 10:12 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page