My 77 450SL makes a noise similar to what sounds like a belt squeal when I am driving. It is most noticeable at low speeds and changes pitch when I speed up. When I back off the accelerator the pitch drops and the noise stops. There is no noise when the car is parked, even when I increase the rpms. The noise is intermitent and sometimes alters pitch when the tranny shifts. I am wondering if it might be a pump bearing that is going bad or perhaps something related to the water pump. Don't think it has anything to do with wheel bearings.
Any suggestions?
Thanks
Mike