Engine running; no belts turning, no pulleys turning - Page 5 - PeachParts Mercedes-Benz Forum

babymog · #61 02-05-2008, 09:19 AM

I would recommend using a thread-lock if the manual prescribes it.

Also, if the manual says to lubricate the threads, then the torque spec is for lubricated threads, an important difference, lubricate the threads.

tangofox007 · #62 02-05-2008, 01:01 PM

Quote:

Originally Posted by jamesNB

I've been trying to locate a big torque wrench; mine only goes up to 150 Nm. I'm thinking about using my 18" breaker bar and my 200# body weight. That should get it close to the 270-330 Nm spec (1.5ft X 200lbs=300ft lbs = about 400 Nm). Then I can go to a shop to check it.
Updates to follow...

Just one problem with going to a shop. Once you reinstall the vibration damper and pulley, you can no longer access the slots in the balancing disc to prevent the crankshaft from rotating. So it would be a lot easier to torque the bolt correctly the first time.

patbob · #63 02-05-2008, 04:29 PM

Quote:

Originally Posted by jamesNB

I appreciate your concern and thanks for the links you provided. I'm thinking of going with the antiseize for three or four reasons:
1. The MB manual says to lube the 18mm bolt
..
3. I think most of the failures are due to the bolt not being tightened to spec or something else going wrong.
4. And the biggest reason--the Germans tend to over engineer things. If an 18mm bolt torqued to 300Nm with three cup springs comes loose, there is probably a reason. Even though the big bolt coming loose would be bad, I think a glued in big bolt coming loose would compromise the "if something is going to break, make it the less expensive parts" principle.

Number four is just a big assumption on my part but comes from a good number of years working on different types of German built equipment (mostly lab equipment). But one thing seems to remain constant, if they designed something a certain way, there were several good reasons.

Isn't the entire reason you're doing all this because the pins shattered and allowed the balancer to get all loose on the shaft nose? Loose parts, especially loose parts under force, tend to chew up everything they are loosely attached to as well as themselves. Whatever you decide, you don't want this thing coming loose until you intentionally want it removed.

The grease reduces thread friction allowing you to get the desired thrust force via the spec'd torque. The loctite will also act a somewhat of a lubricant until it sets, so you'll get clsoe to the desired thrust force, but then it'll set and raise the thread friction even higher, preventing the bolt from backing out. Just make sure the threads are clean of old grease and oil if you use it.

Me? I'd use the thread locking stuff.

t walgamuth · #64 02-05-2008, 05:17 PM

Quote:

Originally Posted by jamesNB

Vibration Damper. No Rubber part between damper and balancer unless the black gunk is all that's left of it.

Sheered Pin. The halves that were still in the balancer.

CrankShaft Snout. The edges of the groove look sharp but you can see some wear from the broken parts. I have no idea what the goo is on the upper left of the housing. Maybe gasket silicone from a previous repair? Any ideas?

Balancer. The grooves look sharp.

Cup Springs, cap screws and the big bold (18mm dia, 27mm head). I haven't cleaned them. Note, no washers on the cap screw. Manual states they stopped putting washers on them Jan 1979.

Let me know your opinions on the grooves in the crank and balancer. Do they look ok? Or should I start looking for a rebuild engine?
If the crank needs to be replaced, I would lean toward doing a rebuild.

The recesses in the balancer upon second look, look a little stretched. Are you getting a new one? I imagine a perfectly tight fit all around the pins is essential to it staying all together.

Tom W

jamesNB · #65 02-05-2008, 10:35 PM

Yes, I am replacing the balancer. It's worn pretty badly.
The bolt didn't come loose with this failure. It was still in there really tight.
I've attached a poor quality cell phone picture of the broken spacer ring. Ouch!

t walgamuth · #66 02-05-2008, 11:32 PM

Ouch, indeed.

Tom W

Dusty-NZ · #67 02-06-2008, 02:01 AM

I had a near identical failure in my 300SEL , the woodruff key sheared and badly scored the nose of the crank. I cleaned it all up , made a drill jig and drilled down the side of the crankshaft/pulley interface, in 2 places, and tapped threads and installed long grub screws , lots of 680 loctite on everything , LOL , still holding on.

Next owner is gonna need a blow torch to get it off............ !

t walgamuth · #68 02-06-2008, 08:04 AM

Quote:

Originally Posted by Dusty-NZ

I had a near identical failure in my 300SEL , the woodruff key sheared and badly scored the nose of the crank. I cleaned it all up , made a drill jig and drilled down the side of the crankshaft/pulley interface, in 2 places, and tapped threads and installed long grub screws , lots of 680 loctite on everything , LOL , still holding on.

Next owner is gonna need a blow torch to get it off............ !

Now that sounds pretty good. The factory can't do it that way for obvious reasons. If the alternative is buying a new crank, this seems like a reasonable alternative.

Tom W