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  #1  
Old 10-30-2002, 09:26 PM
geojer
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300td timing chain

I need to replace the chain on my 84 300TD. I have the standard haynes paperback repair manual. Can someone tell me how do I replace the plastic guide on the left side and the tensioner (do I need to replace them with the chain)? IS THERE A WAY TO CRIMP ON THE NEW CHAIN without buying that special very expensive tool (2X the price of the chain)? if not would someone like to rent one to me? or perhaps someone else is planning to replace thier chain (or several people) and we could collectively purchase one. This is a one use tool, seems a shame to spend so much money on it (I am a poor grad student). I really can't wait to get this thing going, I put 25 miles on it since purchase, it has sat in my garage since.

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  #2  
Old 10-30-2002, 11:33 PM
Old Deis
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The tensioner is bolted in on the upper side of the engine. I believe you will need to take off a shield to get to it. Has three small bolts holding it in. Has a large screw-on cap that holds a tensioning spring. The spring pushes on that banana slide, which in turn keeps tension on the timing chain.
The tensioner is designed to ratchet in. In order to check it you will need to remove it and then pull the shaft all the way out and shove it back into the end that had the spring. If it will ratchet ahead and stay, it is good. If it ratchets ahead and then you are abel to shove it backwards, it is worn out and should be replaced. Some have found the spring broken in there. That is purchased seperately. I replaced my worn tensioner, but not the spring.
I believe you can rent the tool here. I was able to borrow one locally. I have read that it can be done without the tool. Maybe someone else could comment on that.
That plastic guide (banana slide) may or may not need replacement. If it has grooves worn in there you should. Tough to get off. You will need to pull the damper pulley and the black plate behind it to access the pin that hold the slide in at the bottom. The Haynes has a good explanation on how to get that pin out. Using the bolt with a large nut worked ok for me, but I did have to heat the pin to get it out. Was stuck in there.
Biggest thing is to tie up both ends of the old chain and new one whenever they are loose. They will quickly get away form you. If it slides into the engine you could have real excitement there.
I used two vise grips to clamp the chain to the gear. Just roll it ahead a little and reset the vise grips. Stuff rags anywhere the engine is left open. Take no chances on dropping the master link or the temp link down there and losing it. Had a helper and I think that is best. This is not a job I wish to repeat soon, but did succeed with the install of new timing chains on both of my old diesels.
Last point is do not roll the chain in without the tensioner in place. Bad form.
Good luck.
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  #3  
Old 11-01-2002, 01:48 PM
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geojer

After I measure my chain stretch, I will let you know if I am interested in group purchase/rental of a crimper, but I might use the hammer/anvil method.

I think the rental is around $50 from performance.
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  #4  
Old 11-01-2002, 02:34 PM
LarryBible
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First of all, I don't think your engine has a ratcheting tensioner.

Secondly, you don't need the tool. Put the master link in place from the back, slide the plate over the pins and into place. Before putting the plate over the pins, rub your finger over the plate and put the smooth side forward. One side will be sharp on the edges, and the other side will be sharp. You put the smooth side forward so that the pins peen in place over the smooth side. It has more area to be peened against and does not make a sharp edge on which a crack can begin.

Then, place a body dolly or heavy hammer behind the link and peen the front of the pins in place THOROUGHLY with a ball peen hammer.

As warned by the previous poster, take extra care not to drop the chain while rolling it in. You can fish it out, but you will then have to check pump timing, etc.

Good luck,
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  #5  
Old 11-01-2002, 02:39 PM
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I give up Larry, I can not find the difference between your last two posts... or were you just saying it again for Emphasis ?
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  #6  
Old 11-01-2002, 02:54 PM
Old Deis
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Larry, which of these has and does not have a ratcheting tensioner?
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  #7  
Old 11-01-2002, 03:57 PM
geojer
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thanks, found the tool at performance products for 34 dollar rental for 21 days. Unfortunately they don't have it in right now and can't tell me when they will. I am tempted to try the hammer approach, it's usually what I end up using in the end anyway on most jobs. So once I have the tensioner pulled out the "bannana slide" will come right out through the top? looks a bit tight in there.
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  #8  
Old 11-02-2002, 11:00 AM
LarryBible
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Sorry about the stuttering replies.

I know that the M103 and M104 gas engines have the ratcheting tensioners. I have never taken apart a diesel later than the 616 or 617, so I'm not sure about them. I don't think they have a ratcheting tensioner though. The ratcheting tensioner seems to go hand in hand with the single row timing chain of the gas inline engines.

I have never replaced the banana rail except at complete over haul. If memory serves me correctly, you will have to remove the cam sprocket or maybe the camshaft to get it out. Why are you changing it? Does it look bad? They are not bad about breaking like the ones on the V8's.

Good luck,
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  #9  
Old 11-02-2002, 01:45 PM
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Larry, I am not sure what you are using to define ' racheting ' but my shop manual says for the 617.95 that it has a " detent " type chain tensioner... which takes up the slack as the chain stretches... does he not have that engine ?... or are you referring to some other type of mechanism ? In terms of performance detent and ratcheting are pretty close in affect... It is described on page 05-310 of the MB shop manual for the 617.95... I can take a pic if you want to see it...
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  #10  
Old 11-02-2002, 09:03 PM
LarryBible
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The ratcheting tensioners have a number of teeth along the side of the plunger. There is a pawl that catches on these teeth as the timing chain wears. This pawl holds the tensioner in place even after the oil pressure is relieved from the plunger.

The tensioners in the 616/617 does not have this, it really only fully tensions the chain when oil pressure is applied. This means it is slightly loose at start up. I think the detent just keeps it from completely loosening when oil pressure is not present. It does not continue to tighten and maintain tension as the chain and associated parts wear, as does the ratchet.

With the ratcheting tensioners of the 103 and 104, you have to push that plunger all the way through and reinsert it in from the back. This gives enough slack to put everything together, then when the engine is started, the plunger will ratchet as far as the chain will let it go, finding its tense position.

Have a great day,
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  #11  
Old 11-03-2002, 08:24 AM
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Larry, I even GAVE you the page number... and you still don't believe me ?


From page 05-310 of the MB service manual for the 617.95 engine....

"This engine is provided with a hydraulic detent chain tensioner without valve...
The pressure bolt moves forward from detent to detent in accordance with elongation of chain.Travel to the rear is limited by detents. As a result, the pressure bolt cannot be pushed back when the engine is stopped. Any jumping of the loose timing chain or any chain noise when the engine is started is therefore eliminated. "
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  #12  
Old 11-04-2002, 12:15 PM
Coming back from burnout
 
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.....boy I admire everyone's patience...

...... its really hard to sit here and type out explanatory steps to teach someone to change that chain, we all have different experiences with doing it and different tricks
One thing I want to warn you about is be careful handling the chain, it gets slippery with Oil and slips right through your hands and drops down the front engine cavity at which point it gets very frustrating to extract. Slip some piano wire through the end or a coat hanger during intermediate steps befor you close the chain up so that it wont fall down that cavity
...if this is your first time doing it, please be patient. Anytime you get tired or puzzled, please stop and get on the Internet and ask questions, we will help you.
....if you can get hold of a Digital camera, that could help, because you could take pictures of a situation you dont understand and then post them and ask us...
Also if u dont havethe tool to pull the pins, its quite easy to get long 6mm bolts and use flat washers and deep sockets to make a pin pulling tool, this is perhaps an easier way then usinga slide hammer to get the pins out..
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  #13  
Old 11-04-2002, 03:29 PM
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First, yes the OM617 does have a "ratcheting" (detent) tensioner. Leathermang pointed out it's in the service manual.

Second, I recommend using the proper tool if there's any way you can beg/borrow/steal/buy/rent it. The end plate require pressing on and the tool does that too along with crimping the ends. I know a lot of people have done the hammer/anvil method, but there's an awful lot of varibility there, one person's idea of "peened" is not necessarily another's. The tool eliminates the guesswork. Too bad it's not cheaper.

Third, there is a nifty tool for the OM60x engines that makes it impossible to drop the chain or mess up the timing. It costs a whopping $20 from the dealer. I believe a similar tool is available for the OM617 but I'm not sure on cost. (The aftermarket OM60x tool costs double+ what the dealer tool is, go figure!) Photos of the tool in action are in the following PDF file, which also explains the process in detail (although it's OM60x based the principles apply to OM617 as well: )

http://www.meimann.com/docs/mercedes/OM60x_Timing_Chain.pdf


Regards,
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Last edited by gsxr; 11-12-2002 at 11:07 AM.
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  #14  
Old 11-04-2002, 07:10 PM
Old Deis
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Larry, I just got out of my 1981 300SD with the 617.51 engine and I can attest that is has a ratcheting tensioner. I paid $70 to replace it. Also has a double row timing chain.
gsxr, That tool looks interesting. I did find that using some rebar tie wire (That's bailing wire to Larry) worked ok. Just make sure to get both ends tied up before starting, or you will have a riot on your hands. Those chains can roll into the engine in a flash.
geojer, the banana slide will come out through the top of with the chain in place, but don't replace it unless it is grooved. A real pain to get out and a real pain to get that pin out down behind the damper assembly. Remember that if you pull that off, you will need to follow another set of instructions, including getting a torque wrench that will allow you to torque the bolt back on at somewhere around 200 lbs.
Good luck, and let us know how it goes. I did two chains on my pair of old diesels at one sitting. A new form of torture, I am sure.
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  #15  
Old 11-05-2002, 12:19 PM
geojer
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sounds like peening (sp?) the end over is probably not a big deal, but since this is my first time........probably best to wait for the tool. The slide looks okay, is there any reason to replace the tensioner? is it standard to replace it with the chain? just as pricey as the chainl...anyway to test it?
thanks
jb

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