2003 BMW 745

Noises problem
2003 BMW 745 V8 Two Wheel Drive Automatic 101000 miles

Hi, I seem to have a squeeling noise at the front part of the car like a belt is slipping. The noise is definately from the area that has the belts. This noise only happens when the engine is warm, it only happens when im coasting or at stanstill. If I rev the engine the noise stops, however on allowing the car to idle again it comes back.
The noise seems to slightly lessen when the AC is switched on. Also if I turn the engine off & then switch it on straight away the noise dissapears for a very long time, but again reappears later once engine warms up and car is stand still or when i'm coasting & not touching the accelerator pedal.
It's driving me mad, could it be a belt/pulley/belt tensioner or AC belt problem?
As I say it only happens when engine is warm, when accelerator is not being pressed & MOST IMPORTANTLY it totally stops if I turn engine off & then restart it again.
April 13, 2010.

You have made a reasonable and quite possibly correct diagnosis.

Dr. Hagerty
Apr 13, 2010.
Dear Sir,
Thank you for your speedy response. I will get my friend to take a look at the belt drive systems asap. Could you tell me which system it is most likely to be causing this noise eg AC/alternator etc.
Your input is gratfully recieved.

Apr 14, 2010.
That will be the determination of the technician. It could be any of them.

Dr. Hagerty
Apr 15, 2010.
I have the same problem with my 745I. What did you have to replace?

May 19, 2012.
Both of you, try this to determine the exact source of the squeal: Purchase a 2-3 foot length of 1/2 tubing. With the engine running and making the squeal, hold one end of the tubing against your ear and slowly move the other around the various moving parts of the belt drive system. When you hear the noise the loudest, you're right over the squealing part that needs to be changed.

Jul 25, 2012.