hello all, I am now beginning to fret and stew over my timing chain on my SD. My car currently has 215,500 on odo and I am worried about it. I was think last night that "oh what the heck, I'll just replace it" until I found out that the change out with new tensioner would run me close to $180!!

What ways are there to tell if chain is ok? Valves were adjusted at 202,000 miles by an indy garage (have slip from PO). Should I just open the valve cover and measure the chain pitch, and while I'm there re-adjust the valves? If so, what is orig/max chain pitch dimensions? I have a caliper to measure with, accurate supposedly to .001"


Thanks!

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-Matt

EPA Section 609 Certified MVAC Technician
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Oil Burner Kartel Member #10

Ahh the smell of Diesel Fuel, it's like coffee in the morning!

My Car:

1982 300SD Turbo Diesel (231,500 miles!) RIP

1984 300SD Turbo Diesel Custom (235,500 mi on driveline.) - On Road!!

www.icsrepair.com

At 15K, it's a good idea to check and adjust the valves. They should not be too far from spec.

To accurately check the timing chain stretch requires a dial indicator to be setup on the #1 intake valve, after the valve lash is removed. The engine is rotated until the valve lifts .080". Then the reading is taken from the degree wheel on the crankshaft damper and compared to a known spec. IIRC it's 11 degrees on an existing (worn) chain. Almost all chains that have been in service for awhile won't meet this spec. The question is how much the chain exceeds this value. The manual calls for using an offset key to adjust the valves back to spec, however, there is some disagreement as to whether replacement of the chain is a wise idea if the stretch exceeds a certain amount.

Some folks run the chains over 250K without replacing them. Others replace the chain on principle after a certain number of miles. There is no consensus.

Does $180 include the upper guide rail?

You can eyeball chain stretch to help you decide. Align the cam timing marks then read the degrees on the crank pulley. The cam timing marks are pretty coarse you'd have to average 10 or more crank readings to get a meaningful average but one reading is better than no reading.

Sixto
95 S420
87 300SDL

it could still be in good shape if the oil was changed diligently, so the testing is worth while. if changing the chain i would change the guide rails too and the tensioner. you also can tell by looking at the sprockets i think if there is a lot of wear.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

This link will give you instructions on how to check timing stretch:

http://skinnerbox.steaky.org/Service/W123/w123CD2/Program/Engine/617/05-215.pdf
As you can see you need to get the cam code to do this method.

This one shows how to adjust valve clearance:

http://skinnerbox.steaky.org/Service/W123/w123CD2/Program/Engine/617/05-210.pdf
You do not need the special wrenches. I use 2 regular 14mm wrenches and they work fine.

What you can do if you don't have a dial indicator is adjust your valve clearance and while you have the valve cover off take a few measurements on the cam tower marks.
This will give you a rough idea of where your at.
Then when you get a dial indicator you can get a true reading on the chain.

Also there are earlier and later versions of the chain rails. The earlier versions are white. The later versions are black.
If you have black guides chances are they were at some time replaced.
I'm not saying that if their black they were replaced I'm just saying that maybe they were.

You may want to bookmark that Steaky site.
Do a search on Timing Chain for more info.

Danny

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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So to clarify I adjust the valve until there is 0 lash by cranking it up until I can't get a feeler gauge in there at all. Then I setup and adjust the dial indicator so that the needle sits on the top of the valve retainer and is set at 3mm (although that number really doesn't matter much). I turn the crank until the dial indicator shows that the valve has been pushed down 2mm. Then I check the harmonic balancer for the amount of stretch.

I can do that. I'll take pics of the process as well.

-Tad

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1995 G320
2003 C230 Kompressor Coupe
2005 ML500
2007 ML350

My '81 300D is sitting in the yard as this is being typed waiting for me to pull the engine (which will probably happen over the holidays). It has 242k+ miles on it and the last time I adjusted the valves I did the "rough" chain stretch test and it was showing 11 degrees on the balancer when the cam was lined up. The car starts, idles and runs out good but I suspect is a little low on power (hard to tell). Anyway, I have parked it till I can go through the engine. It is getting a new vac pump, oil pump, new brgs, pistons and sleeves if needed. This is going to be my 6 week "winter" project.

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Jim

You got the idea. Just 2 things. You start with intake #1 "straight up" In relation to the rocker arm. So "straight up" may not necessarily be straight up. The object is to remove as much valve lash as possible.
Click here for picture

And the manual specifically states "Just remove" valve lash. So yes you crank it up but you need to go easy on it.

Danny

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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