Forget my last post. I found a similar one from Feb. 200 that solved my problem. 420 SEL hot and hotter
The water valve had just been replaced in the car so I went looking for the aux water pump. When I looked down past the new valve, I saw the plug and contacts for the new valve, separate. The mechanic had forgotten to plug in the new valve and it duplicated the symptoms of the old, stuck valve. Guess I'd better do this stuff myself instead of trusting a professional.