Squealing noise in motion at 2-25k rpm. Help!

[yogi799]

99 328i automatic, 65k


I have a problem that drives my crazy. Recently I have replaced my waterpump. Everything went well. When in idle, things are perfect. When I drive the car, however, I hear a high pitch squeal coming from the engine area. The problem is that I can ONLY hear this noise when I drive (so I can't troubleshoot it by ear) and it only happens when I depress the accelerator and when the RPM is about 2000-2500. Does not happen when I rev it up while stopped in park or neutral. It sounds totally as if the engine is sucking air thus making the noise - BUT it never did this for the first 65k miles! Does the engine suck more air while in motion? It started only after I replaced the waterpump. Any clues??? Help!

 

[Chicago-Spike]

Maybe the belt? Seeing as it squeals under a load at a certain rpm range and you just put a new H2o pump on the system so the belt is having to pull something that is new again(the old pump will have been worn and wouldn't put a lot of stress on the belt). Not a mechanic here by any means, but that is my past experience, you replace something that the old belt drives and you don't replace the belt, the belt will start complaining.

 

[yogi799]

I think it has something to do with the vacuum/air intake - it does NOT squeal at any rpm while stopped, so that eliminates belt slippage possibility. It only squeals at about 2700rpm when trying to maintain a steady highway speed with the accelerator depressed very slightly. It quits squealing when releasing the gas pedal and coasting.

???????????