94 C280: New serpentine belt way too loose

[Arv]

Hello all:

I just installed a new serpentine belt (length 2170mm/85.5in, 6 grooves) on my 1994 C280 Mercedes car but it has absolutely no tension. I can press down on it almost 1.5 inches. When I start the car, it seems like the automatic belt tensioner doesn't adjust the belt to proper tension. I can see the belt jumping up and down on the tensioner pulley. It also squeaks because it is too loose. I checked and double checked several times with the routing diagram in the owners manual to make sure I have installed the belt correctly. Besides this is not the 1st time I am changing the belt on my own.

So, What is the problem with this belt? Is it the automatic belt tensioner which is the problem? Is there any way I can test the automatic belt tensioner to make sure it is in working condition.

Any help is really appreciated.

Thank you,
Arv.

 

[Bolide]

Wrong belt

Measure the length of the old one. The length is marked on it but I doubt it'll be legible

Nick Froome
www.w124.co.uk

 

[Arv]

Hi:

According to the owners manual, the length for the belt is 2176 mm. I also checked on the old belt I removed and it had 2176mm also on it. So, actually, the one I installed is
2172 mm (85.5in * 25.4).

Thank you again,
Arv.

 

[D3AN]

Doesn't run a clutch type pully on the alternator does it? Not got my data to hand to see if it does, but when the clutch pully seizes up the belt does a fair bit of jumping around, other than that if your certain you've fitted the correct belt, I'd be looking at tensioner.

 

[Arv]

Thank you for your replies. The alternator doesn't have any clutch type pulley. I just has a small pulley on it. Is there any way I can MANUALLY test the automatic belt tensioner to see if it is working properly? If I pull down on the belt from under the car, I can see the tensioner moving back and forth a little.

Thank you again,
Arv.

 

[D3AN]

I have a C180 with a simliar problem, but this is my adjuster damper, like a little shock absorber which is attached to the tensioner, I can also hear it knocking as the engine is idling a little ...... Not 100% sure but I think you have perhaps the same set up as myself as regards the adjuster type, if that damper is faulty will also give you the same symptoms.

 

[television]

This is the layout of the belt

http://www.detali.ru/cat/oem_mb2.as...GM=717.465&CT=M&cat=19X&SID=13&SGR=135&SGN=05

 

[Arv]

Thank you all again for your help. D3AN, I think you have nailed it right on the head. I am quite certain that very long time ago while doing the water pump job, I have seen something like a shock between all the pulleys. This might be my problem. It's very hard to see it from the top or bottom since it is so cramped with my inline v6 engine. I will check carefully tomorrow and see what I see. But this might be it.

The strange thing is that the old belt was just fine till I removed it. I never saw any jumping up and down of that belt. It had felt little loose but I guessed because it must have gotten stretched after being there for 130000km.

Thank you all again,
Arv.

 

[television]

If you put up your Email address I can send you the instructions.

The damper does not alter the situation

 

[Ellsy Tanners]

I am sure Your car doesnt have a automatic tensioner, You must crack of the 19mm centre bolt at the tensioner, then tension the belt via the 13mm adjuster rod near the power steering pump.

 

[Arv]

Hi Malcom:

Thank you for your email. I just checked and I do have the shock absorber behind all the pulleys.

1. So does the automatic belt tensioner mount on this shock?

2. How does it know when to adjust the tension? Does it have some kind of sensor?

3. What is the maximum displacement of this shock absorber?

4. So, do you think the shock is not the problem?

My email is arv2000us@yahoo.com

If you can please answer the above questions, I will appreciate it.

Thank you again for your help,
Arv.

 

[Arv]

Also, I scanned in the routing diagram from my owners manual which I am including.

 

[Ellsy Tanners]

http://www.detali.ru/cat/oem_mb2.as...GM=717.441&CT=M&cat=520&SID=20&SGR=045&SGN=03


Is this your tensioner layout ?

 

[Arv]

Thanks for your reply. It's hard to see everything in the back side with all the pulleys in place on the car, but it does kind of looks like the diagram you have attached. I just attached the routing diagram of my belt in my previous post.

Thank you all again,
Arv.

 

[Ellsy Tanners]

Well I am 99% sure that your belt tensioner is manual and you will have to adjust rod 32 41 in the link, once the centre bolt has been cracked of.

 

[Arv]

Well, what has puzzled me is last time when I had installed the belt about 5 years ago, I didn't have to adjust anything, and the belt I had installed was 4mm longer than the one I have installed now. All I had done was removed the old belt, install new one and I was good to go.

I will look for the rod you are talking about.

Thank you all again,
Arv.

 

[Ellsy Tanners]

So when you put the belt on/off, how did you release re-apply the tension.

 

[Arv]

What I had done was loosen the lower bolt of the alternator, remove the top mounting bolt of the alternator, and then swivel the alternator to loosen the belt tension. Then remove the old belt, put new on and put back in the alternator bolt on top and tighten all the bolts. That was it.

By the way, I looked for rod Ellsy is talking about but I couldn't see it from the top and there doesn't seem to have any place hidden since the water pump is right there.

Thank you again for your help,
Arv.

 

[Ellsy Tanners]

If you can Arv, take some pictures from the top of the engine at the front and post them up

 

[television]

Ellsy,,I have sent him the works instructions for both, with and without the damper, so check your Emails Arv