M103 idler pulley replacement - PeachParts Mercedes-Benz Forum

pawoSD · #1 02-21-2009, 01:38 PM

Soon I will be replacing the idler pulley and belt on our M103.....the belt is old and needs replacement, and the pulley has a chunk missing out of it

.....so it will also be replaced. How does it come off? Its not in the FSM.....is it as simple as undoing a bolt that screws into the holder? It looks simple.....if it is this simple, what is the torque value for the bolt when I put it back in with the new pulley? Is it a good idea to use a drop of blue locktite as well?

pawoSD · #2 02-21-2009, 03:46 PM

Anyone?

Ron in SC · #3 02-21-2009, 04:09 PM

If it's the pulley by the air pump, you just remove the plastic cover and take out the hex head bolt and remove and replace.

pawoSD · #4 02-21-2009, 04:28 PM

Quote:

Originally Posted by Ron in SC

If it's the pulley by the air pump, you just remove the plastic cover and take out the hex head bolt and remove and replace.

Awesome, do you know what the tightening torque is for the head bolt in there?

Also, is it possible to bypass the air pump pulley by using a different belt? Like a belt for a 1986-89 vehicle that doesn't have the air pump?

I noticed in looking up parts that the '89s do not have a air pump and thus have a shorter belt.....they also seem to have a slightly bigger idler pulley....the part is different.

If I were to bypass the air pump with a shorter belt (and am also replacing the idler pulley) should I replace it with the older (and seemingly bigger) pulley, or just the one that is on the car now?

Ron in SC · #5 02-21-2009, 05:09 PM

Don't know the torque value or the answers to your questions.

But I will say you could just unplug the air pump and then it will essentially be another idler pully. As long as the bearing in the air pump pulley is good you should have no problem. Bearing in air pump can be replaced it bad. That's what I did; replaced air pump pulley bearing.

pawoSD · #6 02-21-2009, 05:36 PM

Yeah I am just trying to avoid the air pump altogether....less to fail or worry about. I'm just wondering if its as simple as a shorter belt and possibly the older belt pulley....

Anyone know?

pawoSD · #7 02-21-2009, 11:21 PM

Hasn't anyone else done this before?

S-Class Guru · #8 02-22-2009, 11:23 AM

Check with Hitman; I think he has done it.
I can't find a torque value for the pulley bolt in the manual. Not really critical, maybe about 20 Nm, or a good snug with a 3/8 ratchet handle. Sure, blue Locktite is good insurance.
My manual does show an early engine without the pump, and the belt is 2255 mm long (with AC). Of course, that may be with the larger idler pulley you mentioned.

DG

anthonyb · #9 02-22-2009, 09:54 PM

I did this a long time ago on my old 300E. I don't remember it being terribly difficult, although it might've taken a breaker bar to undo the old pulley. It's a simple bolt on, may 20-30 Nm.

pawoSD · #10 02-22-2009, 10:06 PM

Quote:

Originally Posted by anthonyb

I did this a long time ago on my old 300E. I don't remember it being terribly difficult, although it might've taken a breaker bar to undo the old pulley. It's a simple bolt on, may 20-30 Nm.

Awesome. I'm sure I'll be able to get it off, I just wanted an idea on the torque range when putting it back on.

I've inspected the other items in the belt system and (including the air pump) they all seem to be tight/ok....so I'm just going to swap on a new idler pulley and a normal sized belt for now....I'll double check the bearings on everything when I pull the belt later this week. Now....off to ordering what I need.