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Question:

Slight Water Pump Leak 2001 BMW...help!?

I just noticed a slight leak from my water pump. About the size of my fist. I called one mechanic and was told the 2001 BMW Z3's water pump seals are tight and do not leak with the car is running (engine is hot) but once the car cools the water pump seals expand resulting in the small leak, that I shouldn't worry about it unless it leaks more, the engine over-heats, or dash light turns on. The BMW said I should have the water pump replaced but he may have just said that to make a repair sale. Anyone out there know the truth?

Answer:

on that car the miles are critical for water pump replacement and maybe rad replacement including the t/stat and hoses//you are already over the time period/coolant system failure is imminent
Some seepage through the bearing seal is normal for new pumps. I've never had it happen to me, but that is what I read in the information sheet that the pump came with. If it's leaking out of the gasket area, then you will need to put on a new seal. If the new seal doesn't have anything on it to help the gasket seal such a Felpro's printoseal, use RTV sealant on it and allow it to cure before driving. It is sticky and messy, but it works great.
Rarely do BMW water pumps leak a lot. Most would not even leak when pressure-tested by a mechanic (for a few minutes). But a leaky pump would leak when the engine runs and specially when it is pressurized and allowed to sit overnight. Usually the seal itself does not cause the leak. It is the wornout bearing which allows the pump's shaft to wobble and thus allow coolant to leak. Overheating due to air getting inside the cooling system is big trouble. But bigger trouble still is a catastrophic failure due to failed/seized water pump bearings. Have it replaced. And the previous statement that your car is about due for hoses and thermostat replacement is correct. There is even a chance that the thermostat is allowing the cooling system to get over-pressurized and thus results in coolant leaks. Replacing the pump is good, replacing the thermostat in addition is better, replacing also the hoses is best. If you can afford it.

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