2001 BMW 325I is making a squealing sound, what would cause this?

Question

The sound is like when a belt is slipping. I have tried belt dressing with no success. I noticed that when the engine heats up to the point of opening the thermostat the noise stops. Could this be the water pump making the noise until it begins to pump?

Answer 1

IF it sounds like the belts are slipping then you need to tighten up your belts. Belt dressing wont fix a d**n thing. Tension must be increased on the offending belt or belts.

Your water pump continuously pumps water from the moment you start the engine. The thermostat is what regulates the coolant flow.

Is the squeal conducive to the R.P.M. of the engine? If so then it must be your belt(s). An 01 325I has plenty of miles on it if its a daily driver. I would suspect the belt tensioner has lost its spring load or is about to. It will need to be replaced along with your belt(s) for good measure.  

Answer 2

sounds like it. try some water pump lube..

Answer 3

I don't know why people use belt dressing, its c**p. Need to put on a new belt if its sqealing. And you can't lube a water pump because it has a sealed bearing.