The sounds of the inverter cooling pump are most apparent when the engine stops and the coolant bottle is being refilled. During this time my 2007's pump emits an unstable squealing sound that reminds me of the "ah-ooo-gah" horn sound on an old car. This sound is not unique. At times I have heard it from other Gen 2 Prii. Is this sound indicative of a pump with worn bearings? I wonder if this is the time to replace it? I don't know the car's history re the age of the pump.
Seems like the kind of sound you can hear from a pump running dry. Whether or not anything like that happened to it to cause the damage, I'd say it sounds damaged now, and I'd replace it.
This is not your inverter cooling water pump, which is located behind the driver side headlight. More likely the pump that transfers hot coolant from the engine to the coolant storage tank. And yes, it's not an uncommon noise.
Thanks, guys, for catching that error. I was confusing the inverter cooling loop with the engine cooling loop. Physically where is the engine coolant thermal reservoir’s electric pump? Is the pump constructed differently from the inverter coolant pump? And the coolant diverter valve I replaced years ago on another Gen 2 has a failure mode that sounds a bit like a work ABS hydraulic pump as it “hunts” for the correct feedback signal? This car with the Ah-ooo-gah noisy water pump also exhibits the perpetual diverter valve hunting noise.
Or an old floppy disk drive on a bum disk. Or a wig-wag (well, not really a wig-wag, that's more like click-schlunk).
Yes, perfect description: a disk drive trying to find a track on a bum 5.25" floppy. I think a noisy coolant diverter valve has lost signal from its position-confirming sensor. The fellow that wrote the firmware briefly considered terminating the homing sequence after a few fails but then thought better of it. The endless homing noise serves as an audible alarm that the poor thing needs replacement. And I suspect the ah-ooo-gah squeal from the thermal reservoir pump is audible confirmation that its pump bearings are shot.
The CHS (thermos tank) pump is mounted "behind" the tank itself. Design is similar to the other two electric coolant pumps on a Gen2. No idea if they're swappable. Posted via the PriusChat mobile app.
Gen 2 had a bunch of things that use potentiometers to sense position. Gen 1 had even more. Each one leading to its own peculiar behavior when the potentiometer grew noisy. Some are take-apart-and-cleanable: Some not so much (but maybe fixable if you have an easy source for the right pot):
