Water Pump Question

(If I'm right my post will appear "before the original" question.)

BMW still makes plastic impeller water pumps. They had a bad run back in the mid 90's of plastic impellers that would break prematurely but that is apparently "fixed."

Anyway there's a good chance yours is plastic but don't worry and replace it as normal. Or replace it now if you like they are pretty cheap, but if you do that go ahead and do the radiator, expansion tank and hoses. They are more likely to fail before a plastic impeller.

I have not pulled any plastic ones from M54 engines, but that does not mean that they don't exist.

Thank you for the information!!

I have a 2001 325i E 46. Would the factory installed water pump have a plastic or metal impeller?

It should be metal. The other cooling system components on this car are usually the weak link on these cars.