Leathermang,

Go for it.

Peter

LOL, By your leave sir,....
the problem with posting from the manual is the way they put the writing so far from the picture they are referring to... takes two pictures for each one...
I may ask RLeo for help on this... putting the pics together before posting them...
For any of you guys that already trust me... trust me on this one.... LOL
I realize I am probably at the really slow end of the internet hookups... a slow dial up... but when I get a bunch of pictures on a thread it takes forever to check out the last post and keep up....so I try to minimize it for others in my situation....

Chain stretch...
 

I know we Newbies are a pain, but we know so little yet crave to do so much with our new 'old' cars. Thus, please excuse the carpet-bombing of questions. (We have even more when we buy a cheap/rough one)
How do I check for chain stretch? I need to do a valve adj. just to have a starting point for this car that I trust, and I assume I will check for stretch at that time. I just want to do it accurately, thus my question.
Leathermang, I'm on slow dial-up too.
Jimmy

Newbies can easily avoid being a pain by reading the Sticky at the top of the page about searches... and then following it as far as they can... sometimes they do not know what words to use for a good search... feel free to ask about that.... then actually look at the threads that come up on the search.... and then if any questions persist.... feel free to ask them.... if you have read the already posted items it will show up as good questions... which no one minds answering...
One more point...
Work on getting as much hard paper or CD literature on your car as you can....
This forum can NOT provide enough of the safety warnings and the mulitiple parts changes found on these cars... typically three different designs per major item...
The Factory Shop Manual ( assisted by such things as alldata.com Tech bulletins for corrections to what came from the factory ) PLUS the experience of the forum members can keep these things going pretty much forever.... but it is a lot of reading and learning...( at least to do it cheaply... one can go pay big bucks to some good mechanic if you want to ... but knowledge of your car is about the only way to tell if your mechanic is good..... and honest ).

Leathermang,
By your expression" by your leave Sir" I take you to be a fellow Navyman. I ,however, was not an officer. I was a master chief. I assume you were also a fellow enlisted man. Remember there were Es and Zeros.

Peter

MEASURE IT!
 

braverichard,

You ARE correct. The mechanic you talked to is ignorant! Changing chains at any preset mileage makes absolutely no sense. Chains tend to break when they are either flawed (usually happens in the first 50kmi) or when they are worn, NOT because the odometer rolled over 100,000 miles. Measuring the chain is an easy procedure and takes only an extra minute or so when adjusting the valves and no more then 30min by itself. Recommended replacement is at 5 degrees stretch on the 617's. As long as it's under 5-6 degrees of stretch the chain doesn't require replacement, and furthermore, Mercedes doesn't suggest that the chain is in danger of breaking until the stretch is close to 10 degrees!


Procedure for checking chain stretch
http://home.tiscali.no/henriksen/mercedes/maintenance/TimingChain.htm

I hope this clears up your confusion.


Chris

I've read the area in my FSM about chain adjustment several times and come away with the clear understanding that the chain is checked periodically for elongation and corrected with an offset key as necessary. Upon teardown of a 617 with 248,000 mi (from a parts car) I saw about 5 degrees offset. With a new chain and original woodruff key, the rebuilt motor now measures 0 degrees offset. The original 617 from the car sits next to it in my garage, after 301,000 mi. I've haven't checked it yet. Who wants to guess what it is?:confused:

When I did the chain on my '83 300D, it had about 7 degrees stretch. Big thing to me was the wear on the tensioner guide. It was significant. Replaced the tensioner guide and the left side guide. Royal PIA to do but I made up a little puller for the pins and that helped. Car had about 350K on it and I have no idea when the chain/guides were last replaced. My new '86 SDL had a chain done recently before I bought it. Paperwork says nothing about changing the guides, so first time I have the valve cover off, I'm gonna be looking real close at them.

Autozen, Sorry, that was proper procedure in other branches too....I was a CW2 flying Huey Slicks in the Army...

Leathermang,
Thanks for the lesson on military courtesy. I wasn't aware of that. We do have some quirks in the Navy though. Correct me if I'm wrong, but I believe the Navy is the only branch of service that allows left hand salutes.

It's not routine to replace the guides on a Mercedes diesel when replacing the chain, unless the engine is being rebuilt. I'd question the previous owners maintenance routine, due to the high wear you found on your car BobK. When stretch gets to 7-8 degrees it's critical the chain be changed immediately to preclude destruction of the engine. At around 10 degrees of stretch the valves and pistons begin to collide.

As for using offset keys, they're not meant to be used to correct chain stretch. They're major use is to correct for manufacturing tolerances or for changes resulting from resurfacing the head. when a chain is worn enough for you to notice a difference in performance (over 5 degrees assuming the inj. pump is set correctly) it's worn enough to have the serious potential to break and using an offset key to correct the stretch doesn't change this. Just change the chain when it's worn.

Chris

WRONG WRONG WRONG
 

"As for using offset keys, they're not meant to be used to correct chain stretch. They're major use is to correct for manufacturing tolerances or for changes resulting from resurfacing the head. "

Now be honest with us... you don't have a Factory Shop Manual for the 617 turbo engine .... do you ?

Even without the shop manual... have you computed the amount of head location difference which would be required to produce anything like the amounts of chain location difference we are talking about ?

The offset keys are meant to correct UP TO 10 degees of chain elongation... this is very clear from the manual .... Just as Pete Burton mentioned....

AND that is not the way to check chain stretch which you provided a link to... do a search and you will find a great thead on that... with Steve Brotherton adding the coupe de grace on that cam marks idea....that is only for initial setting of the cams when doing a rebuild... one reason you may be misled is that the picture shows using the cam marks to find the compression stroke for several operations..... but using number one valve position is the accepted , accurate , way to check chain stretch.

leathermang,

Offset keys are used for adjusting the timing when the chain is not at fault (not worn) like correcting for manufacturing tolerances or for changes resulting from resurfacing the head (on a new or rebuilt engine). A M-B diesel engine is quite insensitive to small differences in cam timing. Chain stretch up to 4-5 degrees (about 2 degrees of pump timing error) will have very little( if detectable at all) effect on performance and providing every thing is ok (sprockets not worn) changing the chain will bring timing back to normal, making there NO need to use offset keys!

And that IS the correct way to check chain stretch.
Please see this TSB: http://www.meimann.com/docs/mercedes/OM60x_Timing_Chain_TSB.pdf

The procedure is all very clearly spelled out in it.


Chris

Does an 84 SD have a 617 engine ..... ?

Your reference is for 602,603 and 606 engines....

You do not own a MB Factory shop manual for a 617 turbo engine.... do you ?

You guys are going to go make me double check my genuint paperback OM617 Turbo Diesel factory service manual. But from memory and skimming previously, I think leathermang is right.