Replacing timing chain, what components? - PeachParts Mercedes-Benz Forum

mrNewGuy · #1 07-07-2011, 12:36 PM

I'm going to replace the timing chain on my 84 300SD. Most likely not for awhile, but I plan on getting the parts soon so when I find the time, I have everything already. The service records I have I know the previous owner(s) took it in for general service on a regular basis, but no history of major service. Better safe than sorry in my book.
So, my question is do I just replace the chain or do the tensioner, guides, etc as well? Not sure what parts wear out so just looking for some advice. Using an IWIS chain by the way, I've been doing my reading.

thanks

leathermang · #2 07-07-2011, 01:03 PM

There are some great threads in the archives on this...
everything that is in contact with the chain is the best answer for long life.. including the sprockets it runs on ...

Stretch · #3 07-07-2011, 01:24 PM

Quote:

Originally Posted by leathermang

There are some great threads in the archives on this...
everything that is in contact with the chain is the best answer for long life.. including the sprockets it runs on ...

Very true - but look at the condition of the sprockets before you replace them. I don't know how well replacements will fare compared with the original.

The guides are quite cheap and easy to replace. The FSM says to use a slide hammer but you can use metric bolts and larger sized nuts as spacers to draw the holding pins out of the block. So if you haven't got any metric bolts and nuts I'd buy a selection box of bolts nuts and washers (M3 and bigger). A selection of metric bolts nuts and washers is always good to have about anyway. Most bolts are of 8.8 strength on a W123 so I guess that'll be the same on your car.

Stevo · #4 07-07-2011, 01:37 PM

I would check the chain stretch before going any further, it may be fine for many more miles, all depends on how well the car was taken care of in the oil change dept. At around 5 degrees of stretch I would start thinking about rolling in a new one.

Stretch · #5 07-07-2011, 01:41 PM

In case you haven't seen the DIY section

Chain ELONGATION check is here

http://www.peachparts.com/Wikka/OM617TimingChainStretch

leathermang · #6 07-07-2011, 01:44 PM

I guess that we should cost out the sprockets before deciding... but wear patterns made by the old chain will accelerate the wear....and potentially in an uneven way .. on the new chain... with so much work to change all of it out... and the very real potential that the if the chain was replaced once already... without changing out the sprockets... all new stuff could make this a once in a lifetime job...

Stretch · #7 07-07-2011, 01:51 PM

Quote:

Originally Posted by leathermang

I guess that we should cost out the sprockets before deciding... but wear patterns made by the old chain will accelerate the wear....and potentially in an uneven way .. on the new chain... with so much work to change all of it out... and the very real potential that the if the chain was replaced once already... without changing out the sprockets... all new stuff could make this a once in a lifetime job...

True true Greg - it is the same with bicycles!

But I was just thinking if Febi repackage parts made by others the quality might not be as good as the originals even if they are a bit worn. I guess this is true for other "manufacturers" even Mercedes bits bought from the dealer.

Now I'm just guessing - has anyone got any experience of this? I guess someone like Craig would have been the man to ask as he spent a fortune on his cars - shame he's gone...

mrNewGuy · #8 07-07-2011, 03:52 PM

Quote:

Originally Posted by Stevo

I would check the chain stretch before going any further, it may be fine for many more miles, all depends on how well the car was taken care of in the oil change dept. At around 5 degrees of stretch I would start thinking about rolling in a new one.

Oil was changed regularly (from what I can see) and I need to do a valve adjustment because not sure when the last one was done. I'll check it then and see how it looks. Thanks.

Quote:

Originally Posted by Army

In case you haven't seen the DIY section

Chain ELONGATION check is here

http://www.peachparts.com/Wikka/OM617TimingChainStretch

Thanks, there is a ton of info on here so I'm always trying to find it before I post but usually I still miss it.

Jeremy5848 · #9 07-07-2011, 07:18 PM

If the sprockets are not badly worn, it is a lot less work to replace just the chain, upper chain guide, and tensioner. Replacing the lower chain guides and lower sprocket requires removing the timing cover, which is a lot more work because of the things that must come off first. There are a number of threads here describing how to attach the new chain to the old one and then turn the engine by hand until the old chain is out and the new one is in. Not a bad job, it helps to have a second person to feed the new chain in and catch the old one as it comes out so you don't lose the camshaft-crankshaft timing relationship.

leathermang · #10 07-07-2011, 08:07 PM

TENSION MUST BE KEPT ON THE CHAIN according to the FSM...during that process....