I have a multitude of issues on my 2000 D2 (171k miles). The most pressing to me right now is the noise coming from the engine bay. it is a quite annoying squealing sound that is present when parked. It speeds up while driving but also gets quieter as I go faster. I have ruled out belt squeal by replacing the belt, and it just doesn't sound like a squealing belt. I was hoping it was just an idler pulley, but while listening to each component with a pvc tube, it seems to be coming from the power steering pump. The steering works flawlessly though. My other concern was that it may also be the oil pump. This coming spring I have plans on replacing the timing chain and head gaskets. along with relocating the coils. So I may just replace the oil pump while I'm in the vicinity. Could the power steering pump have an internal bearing going bad? and wouldn't that affect the function of the steering? Thanks for any help.

Head gaskets, plural, suggests a V8 so your D2 will have the Thor as fitted to a similar age P38. Take the serpentine belt off and try spinning all the idlers, the PS pump, alternator and water pump. I've known a water pump to squeal but only on initial start up not all the time and the alternator is also suspect. Any roughness should be felt and that might be a better way of identifying it that listening for it.