Noisy poly V-belt
 

I am having trouble with a noisy poly v belt on my W124 (1994 E280). The belt is in good condition, just slightly noisy. My local Mercedes Specialist (Steve Pollard @ BSG in Blackburn), recommended putting a thin layer of bearing grease on the inner surface. I must admit I was slightly alarmed at this. Being a Chemist I was well aware of the degenerative effect of grease on rubber. However he assured me that this used to be standard practise at the dealerships and works a treat, with no ill effect to the belt. Does anyone have any comments on this solution? I do know that Mercedes now produce a poly V-belt lubricant, part no 000 989 19 60. Perhaps this would be the preferred option.

PS I am based in the UK

What kind of noise...squealing...slapping? :confused:

I am appalling at describing noises :o . I suppose it is more of a wooshing noise. I sprayed some water on it and it duly fell silent for a short while. Once the water had evaporated the noise was back again. My Mercedes guy just said it needed a bit of lubrication, which is where the grease suggestion came in.

I mention this because my belt made a slapping sound whenever it traveled across the air pump pulley. Sounded like the bearings were going out on the pump.

Upon inspection, it was found that a piece of the toothed side of the belt had chipped off. The smooth side looked brand new. Replaced the belt and the sound went away!

I have inspected the belt and there are no signs of damage. Evidently the noise is caused by the slow wear of the toothed surface, and subsequently the belt dust being deposited on the pulleys. Although the belt is still serviceable it makes this noise. Evidently the dealerships routinely greased the belts at service to increase their life (at least they did here in the UK). Ultimately I will replace it, but was just trying to buy some time and avoid unnecessary cost :)

They make stuff called "belt dressing" that's just for noisy belts, found in most car parts stores in a spray can.

I've seen a few posts advising against belt dressing as it can be pretty messy stuff. Just wondered if the grease thing may be a cleaner option. It is applied directly to the toothed side of the belt, and sparingly. Belt dressing is in a spray can and goes everywhere evidently.

Easiest thing to do is obviously to replace the belt. I had the same problem where the belt was getting noisy but was not really visibly worn. A new belt solved the problem. It is also realtively easy to change on n M104 engine. Probably take about 30 mins and $30 or so for the belt.

I have some and have used it with good results. Its a directional spray that is controllable. The idea is to apply it while the engine is running and direct application would be dangerous.

I agree with your view that grease would be toxic to a belt, plus is seems to me counterproductive to put a lubricant on something that is supposed to grab.

It is a strange concept that a lubricant is applied to a drive belt. Even stranger when Mercedes actually produce a product called "Poly v-belt lubricant". Perhaps it is a misnomer. Ultimately I suspect, as Ali Al-Chalabi says, the sensible thing to do is change the belt. The lubricant may just buy me some time, but in the long term it will need replacing.