Fan Belt Noises

They can be a little tricky to isolate

Engine driven fan belts (v-belts) can make all kinds of weird noises. They can squeal, rumble, tick, clack, and snap. The noise can sometimes sound like a bad bearing in one of your engine driven accessories or something coming loose in your engine. Before you panic thinking something terrible might be wrong, try this simple test:

Fan belt noise testing

Problem & Solution

Common among these chassis:

W108 W109
W110 W111 W112 Sedan
W111 W112 Coupe
Classic Sedans

Get a couple cups of water in a bottle or jug (or you can use a spray bottle if handy). With the engine running at idle poor it right on the belts. Do not stand to the side or you will get wet! If your noise is belt related it will go away immediately when the belts get wet. In a short time the noise will come back but if you pour more water on them the noise will go away. If the noise does not go away then you will know that it is something mechanical and you will have to do further troubleshooting. In some cases you can take one belt off at a time and run the engine to narrow your search.

SOLUTION: If your belts are making noise, first try tightening them. If the noise persists buy new Continental belts (do not buy cheap belts from local parts store) and replace them all. I have had no success at all using any type of belt-dressing or lubricant. I have tried most of these products but the noise always seems to return.