Drive Belt Dust
 

Hello everyone. My car had gotten into the habit of destroying belts (2 in about 30 miles) and my tech spent some time filing down a few pulleys that had bent grooves. The belt is still on after about 200 miles but there is black dust on the bottom of the belt and after a drive you can sometimes faintly smell cooking rubber. Is this normal for a new belt or are the pulleys still biting? Thanks.

A new belt should have to be "broken in." If you smell rubber "cooking," then you are going to blow another belt.

How...
 

did you get bent pulleys? Was car in an accident?

A lady had reversed into the front of the car, but as much as I want to blame her for all of this I really don't think its her fault. The first time the belt came off the the coolant return hose had broken at the top of the radiator and the hose+metal clamp got caught in the pulley/belt/visofan area, spinning around and presumably knocking into the pulleys. This bent some of the grooves out of shape.

Thanks for the advice Matt. The car broke down again today and while the belt is still on the instrument cluster lit up all at once and the car started to heat up. That makes 8 times in the last ~200 miles. It used to be so reliable too...

If you didnt already know, sorrry to point it out if you do, when you lose the belt and the alternator is not longer being driven, you typically have all the instrument cluster lights dimmly. You lose electricity and all the sensors voltage drops and the indicator lights all come on. It is typically the sure sign that the belt is off while driving. Also, the ABS light can be a reliable indicator sometimes since the voltage drop seems to happen there first and the ABS sensors will indicate trouble and the light will come on.
at least 3 times in various cars, I have seen basiclly the exact moment my car's battery has dropped in voltage after an alternator has died while driving. The car would then be on battery and the battery begins to drain down until eventually the voltage is low enough to drop first at the ABS sensors and turn on the light. it goes down hill from there and lots of other things start failling and losing power. It is time to turn everything off you can and search for a service station, Fast.

Crhenkel, you are absolutely correct. The two incidents I am talking about are not the same, however. When the belts were tossed, the cluster did indeed light up. In the most recent instrument cluster incident, which is here: http://www.peachparts.com/shopforum/showthread.php?p=1588823&posted=1#post1588823
the belt is still on the vehicle. From earlier posts I think it is pretty clear that more pulley work is in order, but that still leaves my latest incident...

A combination of heat, several belt changes and a pulley issue could have just resulted in a belt slippage and it would result in the same situation as a thrown belt. ANd could seem to be working at a later time. i might check over the belt, pulleys and the tensioner closely. Belt dust is a good indicator of slippage

What model car are we talking about here? Destroying a belt in such short mileage means that something is siezing up (aircon, idler pulley, power steering etc) or the belt is rubbing badly against something. Having had previous accident damage then something could also be bent and out of alignment. Iwould suggest that you find your self another tech! (lots of somethings - sorry)

Badinfo, with the belt off have the "tech" check that all the accessory (alternator, A/C compressor, power steering pump, air pump, idler, fan, water pump) pulleys turn easily ... one or more are likely seized which results in a new belt quickly self-destructing. Although if something is seized the belt would likely screech too ... hard to imagine a tech failing to hear that. Also, have the tech check that all the pulleys are aligned properly and that the damaged pulley grooves are near-perfect ... otherwise replace that pulley. Another possibility is that the belt tensioner is shot. Is the tech MB-trained or one that works on any type automobile? Best to have a knowledgeable tech work on your MB automobile.

GOod point on the pulleys, Ferdman. They are all typically $12-40 online and can easily be changed in little time. Trying to get a damaged pulley back into the condition it needs to be in to be reliable is not worth your money to pay a tech to do it and still not know if it is 100%. Replace any suspected pulley since they can not be made to be "near perfect" and be reliable if you already have belt issues.