This test will either confirm or eliminate a combustion problem. If you do it properly it will be very valuable.

If one cylinder is the culprit, you're going to get the "Whoa" moment!!:eek:

With only going off a youtube video, my 602 engine's front serpentine belt tensioner assembly had a bad bearing in it, and had some free play which made it rattle at an idle. The center bolt through the pivot arm can get loose (pray it isn't or hasn't egged the threads yet..)

Ok, maybe a stupid suggestion, but it's really hard to diagnose a sound sometimes in a video. Anyway, to me that sounds exactly like when my motor mounts were getting tired on my 420sel and the fan blades where barely hitting the fan shroud at the bottom. The shroud is adjustable so I pushed it down a little bit, and problem solved. The shaking of the engine was enough that the fans blades only randomly hit and the sound would go away under acceleration.

if you are still having problems with the noise, I'm not far away... I could assist.
PM me.

Your video does sound like it could possibly be the fan hitting the housing. Do check that. It is kind of random which would be from the engine vibration hitting the stationary shroud.

Just got back from doing a body swap on a friends land cruiser (lot of friggen work)

Tried the injectors not that...... i'll look in to the belt and the fan shroud as it from the start sounded like something up front but it is hard to pinpoint a sound like that and does go away under acceleration some time.

vstech, I would love the help if you can spare it, I live about 1000 yards from Mt Holly just over the river off of mt holly/hunterville rd (near the sonic)

Recently unemployed so have lots of time to play with this, been using most of my time to try and get my garage back in order.

Not the fan shroud,

is there a way to test for this or just have to get to it??
Either way I need a new belt anyway.

guess I got a few parts to buy to see if that is it

A previous poster had the test, to use a piece of wood to put pressure on it. This is done with the engine off:
On the top mount where the spring rests, if you have to ever remove the spring, use a rod that fits in the hole for leverage, to take the tension off of the belt. You could then move the center pivot (with the pulley) side to side to check for play.

Getting back to this..... got a new belt arriving tomorrow... mine was chewed up.

While taking the old one off I will run the car for about 20 seconds (with belt off) to see if the bearings or any part of the belt tensioner is making the noise.

If not its back to square one.

I'll report back with what I find.

Ok got the old belt off.... damn it was bad.

Started the car with the belt off and it sounds just how I would expect a late 80s MB diesel to sound like.... so it is certainly a bearing somewhere in one of the pulleys.

Would it be the idler pulley or the belt tensioner assembly. I understand both have bearings in them.
I may just replace them both but I am under an extremely tight budget right now due to being laid off and going back to school for training in another field. I need to get this thing going so I can return the loan of a family members truck.
So far i've found a febi tensioner
PeachParts FastLane Mercedes Parts Store

and a URO one on rock auto..... i've read bad things about both of them but can't really go with anything more expensive (just need this to last till I get back on my feet and then I can put more quality parts back on it)

The URO one is around $25 from rock auto and the febi one here is $71, so from these two which would you choose??? Or does someone have another suggestion??

I'll get a video up of what it sounds like with no belt to show the difference as soon as I find my camera.

You don't want a Uro replacement for something as critical as the tensioner arm. Get Uro valve cover gaskets and antenna masts if money's tight.

With the belt off are any of the pulleys wobbly?

I posted this a few mintues ago. Might be of some help - http://www.peachparts.com/shopforum/2867466-post34.html

Sixto
87 300D

Ok so the Febi is the way to go or is there another option that won't kill the bank?


I'll check all the pulleys tomorrow off to school now for some good old re-training

Someone talked about replacing the bearing in the tensioner arm for whatever the right bearing costs. The story's in the archives somewhere but I don't think a part number was ever shared.

Sixto
87 300D