E300D timing chain stretch (W210, OM606NA)
With my '96 E300D's engine (W210, OM606NA) now over 277,000 miles, I decided to check for timing chain wear. After pulling the valve cover (a lot more work than the same job in my OM603) I inspected the timing chain, [exhaust] cam sprocket, and the spur gears that transfer motion from the exhaust cam to the intake cam. I could see no visible wear. Pulling up on the chain (as if I were trying to lift it off of the sprocket) produced almost no movement, indicating minimal chain wear.
Next, I turned the crankshaft (27 mm socket and ratchet) towards TDC until I could slip a 6 mm bolt through the holes in the intake cam gear and the first intake cam bearing cap.
When the holes were aligned so that the bolt was a slip fit, I checked the alignment holes on the two camshaft gears. They appeared perfectly aligned, as evidenced by the red line I Photoshopped into the picture.
Finally, I checked the scale on the crankshaft and found that there was almost exactly 1 degree of chain stretch. Since 5Âº or more is considered "time to change the chain," this means that the chain will likely be good for the life of the engine. Should the chain break some day far down the road, that too is "the life of the engine."
I attribute this longevity to Mercedes' good design and the care that the three POs and I have taken to keep the oil clean. A word to the wise: remember to remove the 6 mm bolt before replacing the valve cover!
Discuss this DIY here.