Info on how to replace timing chain tensioner & upper chain guide - PeachParts Mercedes-Benz Forum

bodyart27 · #1 10-14-2003, 12:14 PM

As my 84 300SD has 183K miles, I'm to the point were I want to tackle the timing chain. It seems like it is recommended that the timing chain tensioner and upper chain guide also be replaced at the same time. **************.com sells a kit with the aforementioned parts for about $134, which seems reasonable.

Thomaspin's wonderful site covers the basics of replacing a timing chain (albeit a different engine), but does not go into how to address the timing chain tensioner and upper chain guide.

http://www.pindelski.com/cars/W126/W107_timing_chain/W107_timing_chain.html

Once I have the valve cover off, will how to address the timing chain tensioner and upper chain guide be obvious or do I have to tear down more of the engine to access these pieces? Is replacing my engine's timing chain as straightforward of a process described on Thomaspin's site?

Thanks everyone...

Judge · #2 10-14-2003, 12:27 PM

regarding the timing chain tensioner and upper chain guide, I'm working through the same problems right now, in the thread, Nailing or other Hope that has some helpful information.

There are lots of threads on rolling in a timing chain. Most of the difference of opinion is on what is the best way to close the final link.

#3 10-14-2003, 01:47 PM

Rolling in a new timing chain can be as straighforward as Thomas describes. Just don't drop the chain down into the abyss. That can give you a few moments of terror.
Best to set aside lots of time to check and then re-check your work. This is not an extremely complex job, but it is not simple either.
When replacing that lower guide, sometimes called the banana slide, remember to remove the half round cover from just above the crank. It looks like you should be able to pull the lower roll pin without removing that part, but you can't. Don' tknow if that kit includes new roll pins, but if not then get them before you start the job. You should replace them too. BTW, that small cover just protects the front seal. It does't hold oil or anything.
Nothing to be afraid of really. Just be careful. Once the chain is set turn the engine over through several cyles to check, then re-check the timing marks. If it is off that can be easily fixed at that time. Just loosen the tensioner and the chain can then be rolled link by link over the cam sprocket into the corrected position. Use some wire ties or clamps when doing this. Then check the timing once again. A few of us have found the timing can be off by a tooth and it does not seem to show up on the intitial check. So the smart move is to roll the engine over many times and check the marks. One tooth is about 14 degrees, so it will show up clearly enough if you look.
Good luck with your project.

P.E.Haiges · #4 10-14-2003, 08:44 PM

Bodyart,

Have you checked the elongation of your timing chain? Having 185,000 miles is no reason to replace a timing chain if the cam is not more than 4* late.

MY '80 300SD has 244,000 miles and I'm not about to replace the chain because last time I checked the cam timing, it was less than 3*. However I did replace tje chain tensioner because it was jamming and not keeping the chain tight.

If it ain't broke, don't fix it.

P E H

turbodiesel · #5 10-14-2003, 08:49 PM

How are those alternator brushes?

bodyart27 · #6 10-15-2003, 12:08 AM

1) alternator brushes - already swaped that for a new KAE unit (preventative) - the old one didn't look that worn (had been changed fairly recently)

2) regarding the stretch, I haven't pulled the valve cover off, but I just got my valve adjustment wrenches in from performance products, so I'm wanting to tackle that job at the same time

I know the history of the vehicle (it was my mom's until this year) and I know id had regular oil changes

so is the prudent thing to do, if the stretch doesn't look severe, is just do the valve adjustment and forget about the timing chain for 15K until the next valve adjustment is needed?

BoostnBenz · #7 10-15-2003, 01:57 AM

It takes a long time for the chain to elongate bad enough to be changed. Perhaps you can check it every 15k miles or so but I wouldn't count on changing it next time if it doesn't need it this time. It can be as bad as 8* late without "having" to change it, most say 6* is enough.

P.E.Haiges · #8 10-15-2003, 02:06 AM

bodyart,

The prudent thing: check the cam timing before replacing the chain , yes you got it.

Always test, measure and diagnose before you replace parts.

IMHO, 15,000 miles too soon for next valve adjustment on older engines. I checked the valve clearances on my '79 300 SD at 25,000 miles since the last adjustment and not one valve needed adjustment. I think that's because the valves and seats work harden and need less adjustments on higher milage engines.

Measuring the valve clearance before you loosen any of the adjustment nuts may save you a lot of work and time. I'm guessing a only a few or none of the valves will need adjustment unless its been many miles over 25,000 since the last adjustment.

P E H

bodyart27 · #9 10-15-2003, 12:19 PM

thanks guys for the responses!

I'll definately do the valve adjustment first and check the stretch and report back in a couple of weeks on how bad it was (this weekend is not a good weekend). I'm crossing my fingers that it is not bad (mom was actually pretty good about her oil services!.

With the Factory Service Manuals, the right tools, and Thomaspin's web site I think it should be pretty straightforward. I just replaced the McDonald arching fuel return hoses between the injectors with longer lengths (again, thanks Thomaspin!) so I'm ready to go.

Last Question:

Anygood way to see if the valve cover is warped or just torque to spec and hope for the best? Is this an issue with are cars typically?

P.E.Haiges · #10 10-15-2003, 01:06 PM

bodyart,

Chain stretch is a misnomer. The increase in length is actually caused by wear in the holes and on the pins in each chain link. Elongation is a better word for the increase in length.

To make the measuring and setting of the valve clearances easy, get .003, .005, .013 and .015 inch feeler gauges and use as go/nogo gauges. Using these sizes will set or measure the valve clearance to nominal + or - .001 inch. Just set the valves on the loose side when using the .003 and .013 inch guages.

P E H

bodyart27 · #11 10-15-2003, 02:32 PM

I bought the feeler guages from performance products when I ordered the wrenches. I don't have them in front of me, but they had quite a few "feelers" in the pack, so I'm hopeful they have the onese you mentioned

BoostnBenz · #12 10-15-2003, 05:53 PM

The camshaft cover normally doesn't warp or twist, even if it had a little bit the new seal has so much sponge to it that it'd probably seal anyway. Just make sure the seal is on there correctly before tightening it down (very light torque here), my cruise control unit always seems to make things a little more interesting.