BMW Repair: 2000 540i sport, power steering fluid, snow flake

Question
As stated in the subject line I have a 2000 540i sport, I have been hearing a squealing sound coming from the engine. I figured it was a problem with some belt or pulley or something. When I took it to the mechanic they said the problem was the belt tentioners and replaced them and put on a new belt. 2 days later the noise came back. I took it back to them.. this time they said it was the water pump and fan clutch. They replaced the parts and the next day the squealing was still there. I can hear the noise when I start the engine and drive. The noise seems to go away when I engage the clutch, but when I press the accelerator I can hear it again. It seems to be a constant noise. Whith all the belt driven components they have already "fixed" what else could be causing this problem?  

Answer
Richard, If you pour some water on the drive belts with the engine running and the noise stops then the belts are most likely not the issue as you have found. Does turning on the air conditioning make a difference? (snow flake button). Power steering fluid level okay? Could be any engine accessory (powersteering pump, a/c compressor, alternator.) You have eliminated the water pump. Take the belt off the a/c compressor to eliminate this component. You need to use a mechanic's stethoscope to pin point the noise. You may want to switch Repair Facilities. I would take a test drive with a BMW dealer technician (not service writer) and show him what noise you are refering to. That is the best way to get results. It sounds as though the last shop couldn't tell if the repair was successful or not.
-Evan