Belts flipping over and coming off????? - PeachParts Mercedes-Benz Forum

waybomb · #1 11-22-2008, 12:45 PM

Here's a new one for me.

I replaced all the belts on my 1987 420SEL a few weeks ago. This would be the air pump belt, the ac belt, the alternator belt, and the two ps belts.

Last week, the alternator belt rolled over. I figured I probably made it too tight, as that is easy to do with the set up. So I tighted it up a little less.

Yesterday, all the belts came off! None damaged.

The accessories all turn freely, the pulleys are in fine condition, there's nothing in the grooves, none of the bearings on the pulleys are loose or wobbly.

Any idea what is going on?

I'm thinking I am making the belts too tight or too loose. Does somebody have a detailed procedure I can review?

I must have put a few hundred v-belts on in my life and have never had anything like this happen.

Thanks in advance!

TMAllison · #2 11-22-2008, 12:50 PM

Perhaps one of the pulleys is out of alignment (offset) with the others.

waybomb · #3 11-22-2008, 02:01 PM

Nothing has been moved and everything is lined up.

Pooka · #4 11-22-2008, 03:57 PM

The correct way to tension these belts is to tension them up and then try and turn them 90 degrees. If that is all they will go then they are correct.

In other words: After the belt is installed take your fingers and grab the belt somewhere that it is streached out between pullies. Turn the belt towards you. The groove part shoud now face you. If it will turn further it is too loose, if will not turn that much it is too tight.

If one belt walks loose it will slap against the others and throw them off, too.

Pooka

waybomb · #5 11-23-2008, 11:35 PM

So I completely removed the air pump and ac belts.

Drove a few miles. The alternator belt flipped again. The old cracked one did not flip. Only started when I replaced the belts (all of them). I've replaced the alternator belt twice.

Any ideas?

mpolli · #6 11-24-2008, 01:02 AM

Here is a link I found. I would definitely look very closely at the pulleys.

http://www.thirskauto.net/Fan_Belts.html

hey_allen · #7 11-26-2008, 07:59 PM

I'm scratching my head as well.
I'm using the Conti belts on my SEC, and have had no issues with them.
My SD has Goodyear belts if I remember correctly, and again, no issues.

I'd never had any suspicion that V-belt systems could be as picky as that link above suggests, either.

Mine have always been just about trouble free, other than one car that I bought that the pulleys were misaligned on, and even then it worked, mostly...

waybomb · #8 11-27-2008, 02:26 PM

AAARRRGGGGHHHH.

Well, my new metric belts have yet to arrive. I could have bought them here and had them already.

And I am leaving for Europe tomorrow.

Anyway, I triple checked everything today after replacing the rr window regulator in my E430 (that was a very easy job!).

It has to be the belts I installed. Everything spins freely. No dents or foreign objects in the pulleys. Nothing has any wobble in it at all. Everything is lined up as it should be. I jacked it up and climbed underneath. Everything looks fine from down under as well.

I'll post back after the 8th and tell y'all if the new metric belts fixed it or not.

waybomb · #9 12-09-2008, 03:33 PM

On Sunday, I put the correct Continental belts on the PS pump and the alternator.

Left off the ac and air pump just to see if they were part of the problem.

So far belts are fine. They sit in the sheaves deeper. I ran all the electrical accessories I could and turned the wheel hard right to hard left, all while varying engine speed. Belts didn't flutter at all. Drove it for three days ow and all ok.

I think the entire issue was using belts that were not of correct cross section. So, lesson - don't buy belts for your Benz at local parts stores in an effort to save time.

Alas, I now have a high idle. I've performed a search here and will be checking vacuum hoses first, then the idle control black box.

Thanks for all you comments and guidance.

E150GT · #10 12-09-2008, 05:05 PM

Quote:

Originally Posted by waybomb

On Sunday, I put the correct Continental belts on the PS pump and the alternator.

Left off the ac and air pump just to see if they were part of the problem.

So far belts are fine. They sit in the sheaves deeper. I ran all the electrical accessories I could and turned the wheel hard right to hard left, all while varying engine speed. Belts didn't flutter at all. Drove it for three days ow and all ok.

I think the entire issue was using belts that were not of correct cross section. So, lesson - don't buy belts for your Benz at local parts stores in an effort to save time.

Alas, I now have a high idle. I've performed a search here and will be checking vacuum hoses first, then the idle control black box.

Thanks for all you comments and guidance.

Ive learned not to buy important parts from anywhere execpt here or the junkyard. I bought rear rotors from Oreilleys and they didnt fit properly.

STORMINORMAN · #11 02-13-2012, 02:34 PM

Quote:

Originally Posted by waybomb

On Sunday, I put the correct Continental belts on the PS pump and the alternator.

Left off the ac and air pump just to see if they were part of the problem.

So far belts are fine. They sit in the sheaves deeper. I ran all the electrical accessories I could and turned the wheel hard right to hard left, all while varying engine speed. Belts didn't flutter at all. Drove it for three days ow and all ok.

I think the entire issue was using belts that were not of correct cross section. So, lesson - don't buy belts for your Benz at local parts stores in an effort to save time.

Alas, I now have a high idle. I've performed a search here and will be checking vacuum hoses first, then the idle control black box.

Thanks for all you comments and guidance.

I have just replaced a set of NAPA Premium belts on the '91 420SEL that appear to have lasted over 50K miles based upon my records.

There is a need to replace BOTH PS/fan belts together as a set, and I personally believe that more important that both new belts s/b from the same manufacturer than which manufacturer...

Non-withstanding this belief I would agree that Continental is the way to go when you have the luxury of being able to wait until you can get a full set at a rea$onable price. And as we all know, your price may vary.

I always try to carry a full set of (lightly) used belts (I try to remember to replace them before they break) and after last weekend I now have the hand tools needed to replace all 5 belts in the trunks for the '88 I. & the '91.

Pretty simple list, BTW: I bought used Craftsman 13mm box end wrench & 13mm 3/8th drive socket, a Fuller (Drop Forged-Made in Japan) 17mm X 19mm Combo open end wrench, a 6mm Allen head key, for a grand total of $5.00, conveniently had an old 3/8th ratchet and can now replace all 5 if there is access under the passenger side at the front.

My experience is that DAYCO, Goodyear, the afformentioned NAPA Premium line are pretty good belts, especially if they are metric-sized.

Cheers!

p.s. A full set of O'Reilly house-brand belts only cost about $32 and will certainly do in a pinch, or as the spares.

meltedpanda · #12 12-09-2008, 04:41 PM

ahh, glad to help, good to know you got is sorted out, hopefully others will head off this issue in the future with your final resolve