What causes a thumping noise when driving a 2000 Oldsmobile Alero and when turning the steering wheel?

ck the cv joints

first, check your brake pads, the grinding starts when the pad is worn to the rivets that hold it, then the pad starts to crack and break away. once the pad is gone there will be play that allows whats left of the pad to move around.. causing the thump, there should also be some change under braking, like going from a thump to a grind

this could also be wheel bearings.. but my guess would be the pads, and if it got to that point.. i would bet that the rotor is shot as well

This is caused by a defective power steering fluid pump, replace it and flush the system of all fluid.

more like a wheel bearing going bad, from the description you gave it may be the left one

sounds like rack and pinion is gone

Might check, Bushing on Control Arm, Top Plate, Shock Absorber !

When you changed the struts,did you put in complete assemblies with new springs and top bearings?It is usually the top bearings that make noise when turning.Next is worn outer CV joints on the axles.

get a new pump

What kind of noise, if growling and grinding check and replace wheel bearing. If thumping clunking type noise check steering intermediate shaft, makes noise in both directions.

Make sure that u get all the air out by turning the steering wheel from left to right.. And most important make sure the power steering fluid is for GM product.
Hope this helps..