Pump noises

In the second iMiEV that I've driven a significant distance, the coolant pump makes a low drumming sound in addition to its usual high whine and gurgling coolant. Does anyone else hear that, or might we have a bad mount/failing pump?

Are you sure you're not confusing the Brake Pump and the Coolant Pump with each other? One makes a whine, the other a low hum.

Sorry for a confusing description. The coolant pump hum and gurgle on car#2 is accompanied by a drumming/throbbing sound.
Definitely not associated with the usual vacuum pump whine, contactor clicks, or brake self-adjustment clunks.
That oughtta add some scientific precision.
The coolant pump is the only significant sound after 5 seconds of blower purge (on CHAdeMO and Cold Weather-equipped cars) during L1 and L2 charging sessions (unless you can hear the scream of 60 Hertz sinewaves getting their heads lopped off!).

That's very interesting. Do both cars have identical pumps?