Friends: My 1993 300D 2.5 Turbo has accumulated 187,000 miles. It's currently maintained by Mercedes Werks, a terrific independent shop in Seaside, California.

As far as I can tell, the timing chain has never been replaced. I've heard conflicting advice regarding when the timing chain should be replaced. The most common figure I've heard is 150,000 miles, which means I'm overdue for this service.

As a Cessna aircraft owner, I'm a big believer in preventative maintenance. What is the prevailing wisdom here regarding the mileage at which the timing chain should be changed? Should I replace my chain as a precautionary measure?

Many thanks, Mike

 

I believe an old Vacuum Pump is more problematic then the Timing Chain is.

If you do the Chain (I know you have read this but use only an IWIS Chain and Master Link) or not consider replacing the Vacuum Pump.

Has the Camshaft Timing/Timing Chain Stretch ever been checked?

 

Seems like a lot of labour doing checks, rather than replacing every 300k.
At what interval should we check them?

 

I believe an old Vacuum Pump is more problematic then the Timing Chain is. I want to elaborate on the previous sentence first. When the Vacuum Pump goes bad the parts often fall into the Timing Chain/Gears and that results in Engine Damage.
So I fee l that the Vacuum Pump the most likely thing to cause the Timing Chain to fail.


I have not read of any specific intervals to check. You can do an easier but less accurate check by lining up the Camshaft Gear Timing Mark with the Timing Mark on the Bearing Cap or Bearing Tower (depending on what Engine you have). And looking at the degrees the pointer points to on the Crankshaft Damper. (If you have to us a magnifying Glass line the marks up as exactly as possible so it will be as close to accurate as can be.)

When it was new the Camshaft Timing was set at Zero Degrees (Top Dead Center, TDC). If you read any numbers after Zero Degrees that represents a rough idea as to how much wear/stretch is in your Timing Gears/Chain.

Engines of the same milage will have different amounts of stretch/wear. There is some agreement in the various forums that if the Prior Owners kept their Oil clean and used quality Oil that there will be less wear.

If I did the Camshaft alighment check as described above and I got 4 or more degrees past Zero Degrees I would be doing the proper test to see what it actually is.