Hi all, I’m a long time lurker as I’ve had my W126 OM617 for a few years.


I recently decided to purchase a 1995 W140 from Washington state with the OM603.971 because the engine was rebuilt with updated rods in 2012.

In South Dakota, while on the way back home to FL, I had the vacuum pump jump ship. It was an updated style that broke the arm. I reckon it happened because the timing device was badly worn from the first pump failure, but in any case, no pieces fell in the chain. They fell safely on top of the lower chain guide mount flange...

Anyways, after pulling the timing cover to do the timing device and plastic guides, I found some wear on the slide rail liner. Looking deeper, I found something that made me want to puke.

Point where tensioner touches slide rail was destroyed. Probably because the builder used cheap aftermarket parts...

So now I’m pulling the head too.


Bolts fall within the 2mm of stretch which indicates they are good. However, the first bolt I removed stripped the upper part of the 12 points off. This was because I stupidly didn’t seat the bit completely. Thankfully, after fully seating the bit, I was able to remove the bolt.

This leaves me with one bolt that needs to be replaced. Is that something that can be done with these torque to yield bolts? Or must I replace the entire set now?

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1982 300SD- Flatface wheels, double din, 6 Speakers w/amp under passenger kick panel, Buzzer to chime conversion

1995 S350D- Rebuilt rod bender, OM606 rotary vacuum pump conversion

I wouldn't be concerned with replacing only one bolt if the others meet the spec.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

ditto

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Greg
2012 S350 BlueTEC 4Matic
2007 ML 320 CDI
2007 Leisure Travel Serenity
2006 Sprinter 432k
2005 E320 CDI
1998 SLK230 (teal)
1998 SLK230 (silver)
1996 E300D 99k, 30k on WVO
Previous:
1983 240D, on WVO
1982 300D, on WVO
1983 300CD, on WVO
1986 300SDL 237k, 25k on WVO (Deerslayer)
1991 350SDL 249k, 56k on WVO - Retired to a car spa in Phoenix
1983 380 SEC w/603 diesel, 8k on WVO
1996 E300D 351k, 177k on WVO

At least you fuss over things like the factory-trained M-B techs were supposed to (did they?). I wouldn't pull the head because of a little buggered up aluminum well below the head. Was there another reason? Most likely any aluminum bits fell to the bottom of the lower oil pan where they will stay and likely flow out at the next oil change.

If worried, you can remove the lower pan, and that would be a great time to replace the rubber grommet on the turbo drain tube if old and brittle, since easiest to knock it out w/ a socket from below. Definitely don't try removing the upper (aluminum) oil pan since that would start a can-of-worms.

Sure, replace the buggered up head bolt, and only that one. Personally, I would retorque all head bolts and check compression (should have already). If good, I would keep running and not try to fix a non-problem.

Strange that the push-boss on the upper timing guide got beat up like that. Mine often sit a little offset from the tensioner to wear a slight depression. I got a bit too anal and added a copper tube over the tensioner end and boss to align them, when I had the tensioner off. If the copper falls off, it doesn't bother me since the steel timing chain would enjoy just chewing it up. Similarly, I doubt a little aluminum would bother the oil pump if it made it that far. It would just become smeared into a coating on the steel lobes.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Thanks everybody for the help.

As I pulled more bolts, I found the builder mixed different brands and the stretch is all over the place with each different brand.

So now I’m just going to start fresh with a new set of bolts. I really don’t want to take my chances with the aluminum head 3.5!

The buggered up aluminum slide rail should look like this.

I really don’t want my timing chain to jump and grenade the internals...

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1982 300SD- Flatface wheels, double din, 6 Speakers w/amp under passenger kick panel, Buzzer to chime conversion

1995 S350D- Rebuilt rod bender, OM606 rotary vacuum pump conversion

Sorry, I read too fast and thought this was an OM617. That is a different upper rail and looks a bit more delicate. Even if that whole push-boss is worn off, I doubt there would be enough slack for the timing chain to jump a tooth, at least not in an OM617. Good you are being careful. Still if the compression is good and no odd deep noises, I wouldn't be pulling the head off.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans