I think my water pump is shot.

I'm the proud owner of a 2000 M Coupe as of this past Feb - 32 k miles, still looks fantastic. Driving home from work three days ago I noticed the overheat light come on. I immediately stopped and let the engine cool down, and was only a few miles from home - so I don't expect there was any damage. But now I have to diagnose the problem.

I've checked all the fuses - they are fine. (both #16 and the 40A under the dash - #@$%!).

The Aux fan does _not_ come on, even when the engine is hot. Nor does the Aux fan come on when the A/C is swiched on. (I read about other people trying this a/c test - not sure of the significance myself.) These were checked after driving around for a few miles to warm up the engine - stopped and checked the fan as soon as the overheat light came on.

The Aux fan spins freely when nudged - does not appear to be a bearing problem.

The oil temp never goes above 230F when doing these tests. (at least via the dash guage)

In my opinion, the juicy clue is that, after heating up the engine, the left (drivers) side of the top of the radiator is hot - but the right side is still cool to the touch. So there can be no fluid circulating. Or is the radiator just that efficient?

So my current theory is that the water pump is shot, so fluid is not circulating, but the temperature guage controlling the aux fan is attached to the portion of the radiator that never heats up - so it never goes on. (Bently book is on order - I really have no idea where the temperature guages are.)

But, there is no abnormal noise whatsoever, the coolant level is normal and there is no coolant leak. Aren't these the normal symptoms of a water pump failure? And isn't 32k miles a very young age for a water pump to die? (When my old MR2 lost its water pump, @ ~90 mph on the highway, it made a _very_ impressive cloud of steam.)

Could it be the thermostat? Wouldn't this fail in the open (circulating) position?

Perhaps there is something blocking the radiator?

Any other ideas / suggestions greatly appreciated.

Also: I've found that by keeping the a/c on full hot and keeping the rpms below 2.5k then the coolant temperature never rises much above normal - i.e. the overheat light does not go on. So I plan to get the car so the repair shop this way - unless someone tells me this is _not_ a good idea. But I'd say this means the temp sensor/dash guage is working.

Lastly: Any recommendations for good M Coupe service shops on the SF penninsula? Any comments on what a fair price to pay to replace a water pump (or your best estimate of what my problem is)? My other car goes to Peter Pan, but entirely because I have the extended service agreement with them.

Thanks a lot.