is there any way to test a water pump

[trashcop 80s 80s]

This might be a dumb question but I have searched and I can't find any info on it. Is there any way to test a water pump on an 89 325i without having to remove it? The car is overheating, I've already replaced the thermostat and that didn't help.

[Axxe]

Does it overheat on the highway?

[AdamF 88iS]

Theres nothing to test, really. Does it leak?

[trashcop 80s 80s]

I don't know if its overheating on the highway because the temp guage isn't working. Is there no way to see if it is even pumping coolant through the engine?

[///M42 sport]

how do you know its overheating then?

[m42technic]

how do you know its overheating then?

The million dollar question.

[trashcop 80s 80s]

how do you know its overheating then?

Because water starts boiling out of the coolant reservoir and steam starts coming out.

[M-technik-3]

Hello warped cylinder head....

[brodee]

I doubt there is a problem with the water pump if you are boiing over in the resevoir. If the pump wasn't working at all then there would cold water in the radiator and all the hot water would stay in the engine and not be pumped out.

Sounds to me like you have another issue. If the temp guage isn't working then GET it working before you start the car again. Also check your oil first and make sure it's not milky.

[trashcop 80s 80s]

I think the temp sender needs to be rewired because I swapped in a cluster that had a good guage and it didn't work. I also tried a working temp sender and nothing happened. Then I tried grounding the plug for the temp sender and the guage still didn't move.

[trashcop 80s 80s]

The oil is not milky, so no blown headgasket. What else would be causing it to overheat??

[Digitalwave]

The oil is not milky, so no blown headgasket. What else would be causing it to overheat??

Your headgasket can very well be blown and not have milky oil.

[EverWiser]

The oil is not milky, so no blown headgasket. What else would be causing it to overheat??

Just because the oil is not milky doesn't mean you don't have a blown head gasket. It just means that the "blown" part of the gasket is not allowing the oil and water to mix. You could still have a water leak between one or more cylinders and be pressurizing/boilling the water in the combustion chamber causing it to overpressure your cooling system. However, you should be able to see massive amounts of white smoke out of your exhaust if this is the case.

You also might have air in the system and your pump won't be able to move the water properly. My girlfriends '89 525i with the M20B25 engine did this. Once I filled the engine with water (I filled it through the T-stat housing) and bled the air out of the system, everything was fine. Also, you might as well change the T-stat while you're working on everything. It could be opening late which can cause the problem you describe. Just my .02...

[trashcop 80s 80s]

Thanks for the info. I'll go try bleeding the system.

[hotghias]

i recently replaced the thermostat in my eta because the car was overheating. when i dropped the old one in hot water with the new one, the new one opened much sooner. i had thought that failed thermostats only stuck open (and caused cool running) when they failed, but they can do both. the new thermostat definitely fixed the problem.