Now on to my water pump. I think it's bad. Here is my reasoning. It tends to get hot when the RPMs are higher, but stays cool when at lower RPMs--even through stop-and-go traffic.
If the coolant is getting hot, I can shut off the engine, and restart, and it will cool off, for as long as I run lower RPMs. Basically, at idle.
Since the water pump is driven by the engine, the higher the RPMs, the faster the water pump turns.
I believe I have one with a plastic impeller, and the impeller is loose on the shaft.
Of course, the proof is in the pudding, but is my reasoning sound? I don't want to replace the water pump for nothing.