how do I diagnose which part is causing cooling system failure?

[Unregistered]

I posted earlier about my heat sensor coming on.

How do I know if it's my coolant pump or some other cause?

Thanks for any advice.

[632 Regal]

with a vague complaint as you have it could be anything or nothing. When does it over heat? What other symptoms? What have you done so far? Is it a Yugo? They have all sorts of problems.

[Unregistered]

It's a 1990 BMW 525i with 236k miles. It overheated yesterday after driving about 10 miles. The engine temp sensor displayed - the first time it has ever done that. The temp dial went to the red. I stopped for severla minutes, drove a little more then stopped,....until I arrived home.

I started the car this morning and it sounded fine - it was cold of course. However I did not drive it.

[AllanS]

Easiest and quickest thing to check is the thermostat- it might be stuck closed, stopping coolant from recirculating. After that you may want to look at the water pump, which is more difficult and messy to replace.