Q: My 2002 BMW is making a loud high-pitched sound

Hi There, Depending on whether or not the sound comes when the vehicle is moving or not will determine what may be causing this. The following are some possibilities of what could be causing this:

-It could be that the fan belts were installed but not tightened correctly. -There are bearings in the components being driven by the fan belts. One or more of these could be the source of the noise. These bearings could be in the alternator, water pump, power-steering pump or pulleys that tension and guide the fan belts and timing belt. -If the noise is not heard until the vehicle is put in gear, either with an automatic or manual transmission, the cause of the noise could be internal to the transmission (for manual transmissions) or could be a clutch problem. -Other sources could be the wheel bearings, in the transmission or a differential. -If the noise is only heard when the brakes are applied, the brakes are the likely source. Possible causes include worn-out brake pads, faulty brake calipers, not enough or no lubrication on the brake parts or simply low-quality brake pads and/or brake rotors.

I would suggest having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.