Water pump OK?

[Wes]

I have a '96 328i and have just installed a new radiator. The top radiator hose gets hot, the bottom one does not (dash temp gauge is in the middle). I previously tested the thermostat and that works normal in boiling water and cool down.

Could the water pump be bad? How do I know if my water pump is working?

[dave b]

The water pump either starts leaking, seizes the bearing, or fails without warning. Check for leaks around it, listen for noise, and watch for your temp guage shooting to the red in about 30 seconds. That's a bad water pump.

Is the bottom hose supposed to be hot?

[winfred]

it's possible that the pump has a plastic impeller that's bad, sometimes they will get enough traction on the shaft to cool at idle, but will overheat quickly when reved or driven. another weird thing that will cause a hard to find overheating problem, check the small hose that's under the fan shroud going to the top of the bottle, if it's clogged the system will get airlocked and not burp