After 37 years and 26,945 miles since I had the cylinder head off I decided to pull out the Timing Chain Tensioner Rail. It did not look too bad at the time but had some cracks going on.

The lower have is in the process of falling apart.

It is a Mercedes Part and I am assuming the original. The replacement is made by SWAG but it has the Mercedes Star and Mercedes part number on it.

The Rail Pin not pictured has some wear on it but when I re-install it I will make sure he worn part is on the opposite side.

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84 300D, 82 Volvo 244Gl Diesel

729 miles per year or we missing a digit?

I changed mine when I bough the car about 10 yrs ago but have only put 30K on it so it should be good for my lifetime.

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84 300SD
85 380SE
83 528e
95 318ic

You are right I will have to recheck that.

Here is the rechecked mileage 269,455 miles.

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84 300D, 82 Volvo 244Gl Diesel

I think mine had about 285K on it when I changed that guide. I didn't like the way the guide matched up to the tensioner either but I assumed since the tensioner and guide were both new it's how MB engineers wanted it. The part of the tensioner which was suppose to bear on the guile didn't mate as they seemingly should.

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84 300SD
85 380SE
83 528e
95 318ic

Hard to say. On the original the tensioned pushed dead center on that cylindrical projection on the Rail. I don't know if the new one will do that and won't find out for awhile as another of my Vehicles needs work and must be done first.

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84 300D, 82 Volvo 244Gl Diesel

Hmmmm. Interesting post. Got me thinking and researching...

More than 20 years ago now when my 1985 300D had 125,000 miles as oppossed to 220,000 miles today and before I did the work myself, I had a trustworthy independent M-B technician replace (from the invoice):
"1. Timing chain.
2. Spring for tensioner.
3. Oil tensioner gasket."
No mention of the rail and I didn't know any better at the time to ask.

Considering the aforementioned cracks and degredation, I wonder if the original rail is still in there...

A question: What is the current thinking about the mileage interval for replaing the timing chain?

Thanks-

It has actually (on OM617.952 Engines) been well discussed but to no specific conclusion. The below concerns the original TC that came with the vehicle.

The manual shows 3 or 4 offset keys to compensate for the TC stretch and or gears wear. And give no info of mileage when the TC should be replaced.

I asked many years back what member thought caused the TC failure and most indicated it was parts of the Vacuum Pump falling into the TC and gears that was the cause.

Then I asked what they thought caused the Vacuum Pump failure and they seemed to think it was too much end play in the timer/intermediate shaft bushing. That is on vacuum pumps with a piston.

Further back in time it was the bearing balls falling out of the Vacuum Pump Roller due to the plastic cage falling apart. That I guess could happen to either diaphragm or piston type vacuum pumps.

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84 300D, 82 Volvo 244Gl Diesel