Timing chain
 

I have -91 300E-24 sedan with 75k miles. Does anybody know how often the timing chain should be replaced? I have heard some people saying that it should be replaced at least every 75K miles where as others say I don't have to worry about it.
Thanks.

try using the search option. IMHO.- 100K is a preventive way to do it.

On the 6 cyl, you don't have to worry about it. The V-8's are the only ones that need the timing chains checked or replaced.
The reason for this is how long or short the chains are. On the v-8, the chain is over double as long as on the 6 and therefore, a little stretch equals allot when you get to the second cam. Also, the rails in the 6 are mostly made from metal rather than the plastic of the v-8.

If you're worried, take it to a mechanic and have the chain checked for stretch, otherwise don't sweat it.

Most people get panicky about timing BELTS after being conditioned to big bills every 60k-miles by Honda.

On my 190E's, I would do the chain and tensioner about every 150K-miles, just for peace of mind. At that mileage not one was out of spec. Also, on those 'ol 2.3 8V engines, it's CHEAP. Less than an oil change on an SL600:p

I hate to differ, but the rails on my 6 cyl are plastic and you do have to worry about the chain. I never gave mine any thought... until it broke.

Pat yourself on the back for even asking the question.. I didn't!

Michael,

Great response.

Thanks
 

Looks like I´d better pay some attention into it.
Great site!

Michael, I have serviced thousands of Mercedes 6 cylinder engines, I have NEVER replaced a timing chain on one. I have done valve jobs, over and over. I would bet that what caused your breakage wasn't the rails, although it may have appeared that way.
My bet is something else caused this.
I have seen failure of timing chains because of things like camshaft seizure and soforth, but I have not done a preventive replacement on a 6.

And just FYI, the 6 PASI has is different from yours. His has a double roller chain where yours is a single roller.

There is always a first time. I have no other explaination for the chain to break. Either the chain just failed, or the rail broke causing the chain to fail. It may have slipped a couple of teeth until there was valve interference, causing the chain to break. The chain ends look as if it was pullled apart. The engine was not under a great deal of load, it was not accelerating but at highway speed. It was not the valve train or the tensioner, they were OK.

I did forget about the double row chain. I thought I had read posts here that seemed to indicate that the double row chain was no more reliable that the single. I would have thought that the double row is probably over-engineered. To me that would indicate that it is not the chain itself usually causing the failure but another source. i.e. tensioner, sprocket wear, rails, guides...

Thanks for setting me straight.

Benzmac, What would you recommend regarding checking/changing the chain on a 1993 400SEL with 101,000 mi. on the odometer.

The V-8 engines should have their chains changed at pretty close to 100K miles intervals thanks to the length and routing of the chain.

Cheap compared to the potential result...