Just to add a data point to this thread.

I replaced the original water pump on my xdrive35d at 121k miles. The water pump was not leaking, but the bearing was starting to develop a small amount of play.

I was replacing the thermostat due to need, and replaced the water pump for peace of mind. I'm glad I did.

I know that the water pump was original to the car because the gasket was still attached to the other gaskets on the front of the block. And I confirmed through the service history that no part of the cooling system had ever been touched on this vehicle.

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