Chain strech, unknown engine history - PeachParts Mercedes-Benz Forum

martureo · #1 12-30-2011, 02:50 PM

I bought an 1983 300TD from a member of another board that he wasn't able to restore due to unemployment. He hadn't ever hooked the engine up (it was unhooked from almost everything) but he did turn it over every few months while owning it. He owned it for 1.5 years.

So now I'm done repainting the engine bay and ready to put the engine back in. I've adjusted the valves, the engine turns quite easily with the gps out, the turbo is tight (not that it matters to the question at hand) and the oil is a nice consistency almost like it had just been changed.

So I'm trying to troubleshoot everything I can while the engine is out of the car and I checked the chain stretch. I've lined up the mark on the camshaft 5 times and keep getting 5 degrees.

How many degrees does it take to worry? I'm new at engine timing and I've already read through the forums, but I can't find anything that says "danger zone" or "you should be worried". So what can I do now?

04 Diesel · #2 12-30-2011, 03:51 PM

How many miles? If it were me I would change the chain, just to be safe, also replace the motor mounts while the motor is out. It is alot easyer to change them with the motor out.

Brian Carlton · #3 12-30-2011, 05:21 PM

Quote:

Originally Posted by martureo

How many degrees does it take to worry? I'm new at engine timing and I've already read through the forums, but I can't find anything that says "danger zone" or "you should be worried". So what can I do now?

Why would you worry?

The only risk of late timing is a slight deterioration in performance.

If the timing gets very late, say 8-10 degrees late, there will be accelerated sprocket wear due to the increased distance between the pins.

M/B does not have any recommended interval for chain replacement. Personally, I believe that the chain is so overdesigned that it has a safety factor of about 20X when compared to the load that it sees.

If you have an extra $125. laying around and want to keep this vehicle forever, you might consider it.

Or, if you have an extra $10. laying around, you could just get a 4 degree offset Woodruff key from the dealer and return the camshaft to nearly perfect timing.

Either approach would be satisfactory, IMHO.

Carpenterman · #4 12-30-2011, 05:42 PM

You might want to do the 2mm lift method before you order an offset key. The cam marks are known to be "ballpark".

Brian Carlton · #5 12-30-2011, 05:43 PM

Quote:

Originally Posted by Carpenterman

You might want to do the 2mm lift method before you order an offset key. The cam marks are known to be "ballpark".

Agreed!!

whunter · #6 12-30-2011, 05:47 PM

Quote:

Originally Posted by martureo

I bought an 1983 300TD from a member of another board that he wasn't able to restore due to unemployment. He hadn't ever hooked the engine up (it was unhooked from almost everything) but he did turn it over every few months while owning it. He owned it for 1.5 years.

So now I'm done repainting the engine bay and ready to put the engine back in. I've adjusted the valves, the engine turns quite easily with the gps out, the turbo is tight (not that it matters to the question at hand) and the oil is a nice consistency almost like it had just been changed.

So I'm trying to troubleshoot everything I can while the engine is out of the car and I checked the chain stretch. I've lined up the mark on the camshaft 5 times and keep getting 5 degrees.

How many degrees does it take to worry? I'm new at engine timing and I've already read through the forums, but I can't find anything that says "danger zone" or "you should be worried". So what can I do now?

Please read this thread.
Timing Chains Don't Last Forever

Here is more information you may find interesting.

Warning, Danger: Please read this thread FIRST...
Need Automotive Grade Prozac
Need Automotive Grade Prozac = timing chain - PeachParts Mercedes ShopForum

Diesel Timing Chain Links Thread
Diesel Timing Chain Thread - PeachParts Mercedes ShopForum

.

cho · #7 12-30-2011, 05:49 PM

Quote:

Originally Posted by martureo

I bought an 1983 300TD ....... So what can I do now?

Mate, please look at my post

OM617 shakes after overhaull

'cos it might have lots in common with your
either current either very soon to be situation

please get a new chain

regards
ChO

martureo · #8 12-30-2011, 06:06 PM

Quote:

Originally Posted by 04 Diesel

How many miles? If it were me I would change the chain, just to be safe, also replace the motor mounts while the motor is out. It is alot easyer to change them with the motor out.

No idea on the mileage. The odo was slipping a bit (now has been rebuilt and reset to zero) but it displays around 220K.

martureo · #9 12-30-2011, 06:08 PM

Quote:

Originally Posted by Brian Carlton

Why would you worry?

The only risk of late timing is a slight deterioration in performance.

If the timing gets very late, say 8-10 degrees late, there will be accelerated sprocket wear due to the increased distance between the pins.

M/B does not have any recommended interval for chain replacement. Personally, I believe that the chain is so overdesigned that it has a safety factor of about 20X when compared to the load that it sees.

If you have an extra $125. laying around and want to keep this vehicle forever, you might consider it.

Or, if you have an extra $10. laying around, you could just get a 4 degree offset Woodruff key from the dealer and return the camshaft to nearly perfect timing.

Either approach would be satisfactory, IMHO.

I'm just a rookie to engine timing to begin with. My DD 84 300D has 1-2 degrees. I just didn't know if it was something to worry about. Especially since I know nothing about the engine and haven't started it yet.

Brian Carlton · #10 12-30-2011, 07:03 PM

Quote:

Originally Posted by martureo

I'm just a rookie to engine timing to begin with. My DD 84 300D has 1-2 degrees. I just didn't know if it was something to worry about. Especially since I know nothing about the engine and haven't started it yet.

You'll find that Roy links to several articles that ring all kinds of alarm bells due to older timing chains on M/B. However, the setup on the 617 is quite robust and I would not be concerned with the chain failing with 4 degrees of elongation.

There were several links to the catastrophe that can occur if the chain guides fail or the tensioning rail wears to an unacceptable condition. These are all valid points and it would be a benefit to take a careful look at them and not simply assume they are OK.

If money is no object, as Roy suggests, replace the chain on principle.

But, my SD has 230K on the clock with 4 degrees of elongation............and I'll probably defer it's replacement until the elongation gets above five degrees.

Diesel911 · #11 12-30-2011, 08:53 PM

Quote:

Originally Posted by martureo

I'm just a rookie to engine timing to begin with. My DD 84 300D has 1-2 degrees. I just didn't know if it was something to worry about. Especially since I know nothing about the engine and haven't started it yet.

If your Timing Chain Stretch/Wear is really that little nothing to worry about. See pics below I have 2.5 degrees on my and do not sweat it (the odemater had about 200k miles on it).

If the 1-2 degrees bothers you be sure to do the 2mm method because that is the most accurate. The original poster with 5 degrees should surly do the 2mm method.

Some other thoughts:
Who has or knows someone that has experienced a timing chain breakage/failure?
http://www.peachparts.com/shopforum/showthread.php?t=203364

MY Question on Timing Chain Failure
http://www.peachparts.com/shopforum/showthread.php?t=203364&highlight=timing+chain

What in particular causes vacuum pump failure?
http://www.peachparts.com/shopforum/showthread.php?t=204187

New Vacuum Pump Ruined due to too much Timer Shaft End Play (the title from my notes).
http://www.peachparts.com/shopforum/showthread.php?t=258062&highlight=vacuum