I searched the boards about timing chain replacement and wondered if the tension rail and the slide rails needed to be replaced when changing the chain? It looks like the engine needs to be taken down to do this. I was quoted $350 to do the timing chain. I assume this does not include the rails. My car has 197k and oil changes every 2500 miles. Any tips? Thanks! Joe

There are some previous posts on this and they are the basis for my answer (I'm not a pro).

What I remember is, when you adjust the valves, you can check to see if you need a new chain by how many degrees of stretch are indicated. MB recommends 3 degrees is the limit but some of the pro's say 5 degrees.

I also seem to remember the rails usually do not need replacing. Howewer, if it were me, while your in there anyway, might as well replace them.

Anyhow, do a search or wait for someone who really knows what they are talking about to respond.

Regards,

Mr. BILL

90 300SE
85 300D
84 300SD (sold)

Checking the chain is a simple procedure, and replacing only the chain is not $350 worth. Replacing the rails and other associated components is a bigger deal.

Simply remove the valve cover and turn the engine (clockwise only) to TDC, check to see if the cam alignment marks line up. If you do not see the camshaft mark, rotate the crankshaft one more revolution to TDC. If the camshaft marks are more than a couple of degrees late in aligning, you should consider replacing the chain.

If the engine has had thorough and frequent oil changes, it should not be stretched at all.

Good luck,

------------------
Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

I disagree that a 300D with 197k miles does not necessarily require a timing chain replacement. It will doubtless be stretched, but how much. Failure would be without warning and catastrophic. You can do the job yourself for the cost of a chain ($65?) as long as you can rent/borrow the necessary crimping tool. I did. Replace the tensioner at the same time; another $60?). Then readjust the valves. Perform a timing (drip) test and adjust the drip to between 10 and 19 seconds per drip, not the one drip per second in the manual. This brought up my 1977 240D up to snuff at 165k miles. Worked wonders!

Douglas,

Don't get me wrong, it would never hurt to change the chain for preventive maintenance reasons. However, it IS possible for the chain to have such high mileage and not be stretched. For this to be the case though, the oil has to be changed often and religiously. By changing oil VERY frequently, you prevent particulate from wearing the chain.

The standard MB recommended interval will usually not provide a nonstretched timing chain at this mileage. But oil change mania will most likely reward you with a chain that has zero stretch at this mileage. Been there, done that.

Good luck,

------------------
Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

Joe, at 248K I found that my slide rail had a "serious" grove in it and needed replacement.I plan to replace all my rails while the engine is apart.