'93 2.5 Turbo timing chain replacement interval - Page 2 - PeachParts Mercedes-Benz Forum

archibald2 · #16 02-13-2003, 11:25 PM

You provided a very detailed reply to my query. Thank-you. I now feel I have a direction/path to follow. Re: the MB memo and listing of the chassis numbers

Not that I am going to let the matter rest given the symptoms you mentioned, my '93 2.5 Turbo starts with no complaint, idles quietly and smoothly, and does not have any unusual noises emanating from the front end of the engine, etc.

Oldwolf · #17 09-25-2011, 08:17 AM

Quote:

Originally Posted by gsxr

You don't replace the chain based on time or mileage. You replace it when it is stretched. There is a procedure in the manual to measure this. Up to 4 degress stretch is acceptable but I'd change it at 4. At 5 or more it should be done ASAP, and at 6-7 or more you are risking serious engine damage. At 150kmi I'd expect 1-3 degrees stretch if the oil was changed regularly, or even less stretch if synthetic oil had been used.

FYI, there were a rash of OM602 engines that had flawed chains from the factory. There was a recall on this, I forget the details, but basically you measured the stretch and if it was excessively worn in relatively low miles you got a new chain. Not sure if that still applies today...

Here's the replacement procedure:
http://www.meimann.com/docs/mercedes/OM60x_Timing_Chain.pdf

HTH,

Does anyone have a new link to the above file? It appears to be broken. Thanks.

gsxr · #18 09-25-2011, 10:02 AM

Quote:

Originally Posted by Oldwolf

Does anyone have a new link to the above file? It appears to be broken. Thanks.

http://www.w124performance.com/docs/mb/OM60X/OM60x_Timing_Chain.pdf

http://www.w124performance.com/docs/mb/OM60X/OM60x_Timing_Chain_TSB.pdf

I can't fix the links in the original post, because the forum admins took away everyone's long-term edit capabilities due to one or two idjits who abused the privilege. So everyone pays for their mistakes. But that's a different topic...

Oldwolf · #19 09-25-2011, 02:35 PM

Thanks for the updated links.

Oldwolf · #20 09-26-2011, 10:37 AM

So I measured my chain stretch yesterday. Looks like it is 2 degrees as indicated on the crankshaft pulley. The TSB posted indicated a stretch of 3 degrees or greater requires a new chain. I guess I am safe for now.

sixto · #21 09-26-2011, 01:02 PM

You have to decide is when to check again. You might not have a reason to pull the valve cover for a very long time.

Sixto
87 300D

gsxr · #22 09-27-2011, 09:26 AM

The TSB indicates 3°, and the FSM indicates 4° as the limit. I think beyond 4° is the point at which the chain should be replaced... it's not a fun job, and you'll see zero performance gain afterwards (no change in power or economy).

The stretch tends to mostly happen at chain break-in (first 10-20kmi) and should taper off to near zero afterwards, if properly maintained. I wouldn't be surprised if you measure the same 2° after another 50kmi, especially if you use synthetic oil. The late Doc Booth claimed that chain stretch effectively ceased when good (Group IV/V) synthetic oils were used.

Oldwolf · #23 09-27-2011, 09:31 AM

I use Delvac 1300 15w40 at 4k OCI's. What does it cost to have a mechanic replace the cam chain?

Oldwolf · #24 09-27-2011, 09:33 AM

And by synthetic, do you mean Mobil 1 or Shell Rotella T? They are not the same grade of synthetic oil as you most likely already know .

gsxr · #25 09-27-2011, 09:53 AM

What constitutes "synthetic" is a whole separate discussion. Shell Rotella 5W-40 "synthetic" is a fake synthetic, a Group III base stock that is a hydrocracked dino oil. Mobil-1 used to be all the good stuff (Group IV/V base stocks, true synthetics) but unfortunately some of the Mobil-1 lineup has switched to the cheaper Group III stuff. I'm certain that the M-1 15W-50 is now a Group III oil, and I no longer use it. The M-1 5W-40 appears to still be a Group IV/V (for now). I've used the M-1 10W-40 in my gas cars and I suspect that is also a Group III oil, but I can't say for sure.

Most Castrol, Valvoline, Pennzoil, etc "synthetics" are also the fake stuff. Amsoil used to be all Group IV/V, but not anymore; however the Amsoil 15W-40 "AME" diesel oil is still the good Group IV/V oil and highly recommended. I believe all Red Line oils are Group IV/V, excellent stuff, but far more expensive than either Amsoil 15W-40 or Mobil-1 5W-40.

Note that if you are using a "synthetic" oil that is a Group III base stock (i.e., Rotella Syn), you should not attempt extended drain intervals with it... change it as often as you would a normal dino oil (every 3k-5k). For extended drains (10k-15k, with oil analysis) you should use a Group IV/V oil. An easy way to tell the base stock is to attempt an extended drain interval, if the oil consumption is zero for about the first 5kmi, then shoots up to using 1 quart every ~2kmi after that (or, just increases drastically compared to the first 5kmi), the oil is very likely Group III. Then switch to a known Group IV/V oil, and if the consumption remains unchanged to at least 10k, the previous oil was almost definitely a Group III. YMMV, etc...

shertex · #26 09-27-2011, 11:16 AM

Quote:

Originally Posted by Oldwolf

So I measured my chain stretch yesterday. Looks like it is 2 degrees as indicated on the crankshaft pulley. The TSB posted indicated a stretch of 3 degrees or greater requires a new chain. I guess I am safe for now.

Oldwolf, how many miles on the car? I'm assuming original chain. Thanks.

Oldwolf · #27 09-27-2011, 11:48 AM

171K. I assume the original chain too, but cannot be sure. I took pictures of the chain and timing gear if that would be of any help. The timing gear has the word Mercedes molded into it. The head was replaced with a new version sometime before I got the car.