My alternator light came on, and after some very helpful suggestions here I figured the belt is slipping. I got an aftermarket belt (made by contitech just like MB) a while ago as a spare and figured I'd put on that one. I had always wondered about that because the belt has a 2130 on it and the owners manual says 2140.

I put the new belt on and it was so tight that even after disconnecting the spring and the shock, the belt has to be nudged on the last pulley with a flatblade. I started the car, it ran fine and I felt good.

Then I went to drive it somewhere. The belt screams like a banshee when the engine goes over 1800 rpm or so. Constant. So I figure the belt was supposed to be a 2140. I go to MB dealer, pay almost twice what I should for a belt, and then discover that belt was a 2130 too. Plus, the old one I pulled off, was MB, and was a 2130.

So the question is this: Is there a way to put the belt on wrong that it looses just that little eensy bit of slack required but the engine still runs w/o throwing it? Is this normal and it just stretches out after a couple days? Am I trashing all the bearings in the pulleys? (This thing is REAL tight - the shock is all the way compressed, the lever was hitting on the block, and the spring is fully extended.)

Any suggestions would be greatly welcome!

thx

Mine is a 99. When investigating bad vibrations at the tensioner assembly (ultimately found to be caused by a partially collapsed motor mount) I found the dealer listed 3 belt lengths which were determined by Vin.

Mine with normal options was the 2130MM length.

During my "dark days" (6 months of hell where I ate up numerous tensioner components) I did have one 2130mm belt that measured 2156 after 30 days of use, so they do stretch.

You could test (spin by hand) that there is no drag on any pulley causing the squeal.

If you are comfy you have the correct belt and that all pulleys are good, perhaps it is time to apply some belt dressing, check the motor mounts, or to give it some time......

PS: tyeing some string to the belt between the alt and harmonic balancer pulleys and fishing the end up between the tight spot between the tensioner and roller pulleys makes getting the new belt on MUCH easier.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Just a thought, as I think I remember running into this the first time I ever changed mine:

Are you ABSOLUTELY SURE that you're routing the belt correctly over all of the pulleys? There's a diagram in your Owner's Manual that gives a fair representation of it.

Keep us posted.

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2005 Pathfinder LE
2001 E55
1998 M3
1982 320i

If the belt is 'screaming', then something is in a bind, or WAYYYYYY loose.

You need to check all the idling pullies, you need to make sure that everything is 'free'.

10mm of belt isn't going to make much difference. Personally, I'm a gates fan, and I'm sure I'll 'piss off' a bunch of people when I put a NAPA belt on my MB (but I already have one on my Porsche).

I'd say, check all the pullies, check the tensioner, check, check, check. Heck, it's just a serp belt. It's not rocket science.

You're right...don't use anything but Contis on a Benz! I learned this many years ago when there was a difference in the pitch on the belts and gates would wear out much faster than the continentals...from then on I always insist on the contis, they are who make the belts for MB.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Thanx to all - I'm apparently getting old and dyslexic... I looked at the diagram over and over and checked and rechecked the belt. After several times, it all of a sudden became clear - I pulled the belt loop above the alternator instead of below it. No wonder it squealed - there was almost no grip on the crank pulley... ;-)

Thanx to TM though - the string idea is great!

Now I drive it for a bit and hope the batt charge light doesn't come back ;-)

Thx

It's an easy mistake to make so don't beat yourself up...I'm sure there are some techs out there doing this for a living who have made the same error.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz