strange pump like sound

I've never heard that one. It almost sounds like windshield wipers.

Tom

 

... I wonder if that's supposed to be the inverter coolant pump?

When you you hear this sound?

 

was this ever resolved, or is the sound still there?

 

Did anyone find out what this was... I have had the exact same sound for 8 years or so?

 

brake accumulator

 

The sound in the .wav file link in #1 is clearly not the brake accumulator. I don't know what it is, but the OP was driving a 2007, which would have had the coolant control valve, which sometimes ends up repeatedly 'hunting' for position when its position sensor has gone flaky.

 

Ok I just started getting this noise.
My theory about the more you know about Prius issues the more likely they will occur may be coming true.
It is a faint pumping noise, it doesn't seem to be affacted by pressing the brake, but seems to be behind the brake pedal.
I don't hear it outside the car when I listen near the back of the driver's wheel well.
It happens when driving and when I stop, car in park, before I turn it off I can hear it still pumping.
Sounds a bit like squeaky mattress sex, well the link to the WAV file above still works too.
Doesn't seem like it is a coolant since it doesn't whir, but "pumps".
@ChapmanF says it is clearly not the actuator, I am guessing that does the "buzz-click", but what else would be needing that kind of pumping action?
I can let whatever it is break before I worry about it, but if a brake fluid change or something buys me more actuator lifetime let me know.

 

First thought is that it might be a failing air door actuator for the heater-A/C system. There are a number of ways to check that system for codes in the ecu.

There's some button pressing you can do (search the forums for a procedure) to display some 2 digit codes. Or Techstream, or Autel Maxi AP200, or CarDiag to pull proper OBD codes and data.

Maybe you can get a hand up under the driver's dash above the throttle pedal and try to feel the actuators for vibes that match the noise. Also you can turn the A/C on low fan then change one setting at a time and listen if it affects the noise. (Dash, pause, to Floor, pause, Defrost, then change temperature up or down 10° at at time.)

Posted via the PriusChat mobile app.

 

You can't just conclude it is "pumping action" because of the way it sounds. There are a bunch of things in the car that will make a washing-machine-agitator, squeaky-mattress, back-and-forthing sound. If "pumping" is the only thing that sound makes you think of, then "pumping" is what you'll think, but you'll be wrong.

What you are probably hearing is a servo positioner that has a position feedback sensor. The ECU that controls it wants it to go to a desired position, so it looks at the sensed position, compares that to the desired position, and sends the motor the correct direction. When the sensed position matches the desired position, it stops.

There are three of these inside the cabin, in the heater, to control the doors that control the air inlet, selected outlet, and temperature. There is a fourth one, out under the hood, that controls a coolant diverter valve.

All of them can go flaky in the same way, where the position sensor starts sending electrical readings that jump around. Because the ECU is trying to hold a given position, when it sees the sensed "position" jumping around, it drives the positioner motor back and forth, always trying to get back to the position it wants. Back and forth, back and forth, back and forth.

When it is one of the three door servos in the heater, it's louder inside the cabin, and sounds like the sound file attached in this older thread.

When it is the coolant control valve, it might be louder out under the hood, but it's the same kind of sound, sort of like a washing machine agitating.

In none of those cases is it really pumping anything. It is just a door or a valve being shoved repeatedly back and forth, back and forth, back and forth....

 

Many thanks! I will focus on the climate control system. That makes sense if it goes away when I turn the car off, I would assume any coolant or brake related noise to be able to run a bit after the car is off to push coolant to the tank. I also replaced the coolant control valve with OEM several months ago recently and have been vigilantly checking coolant level. I am using my AC more now that I got it to hold a charge, and the car defaults to 'recirc off', so I hear doors moving as I adjust it and play with the Temp to keep the compressor running at a lower speed since it is starting to zap my HV battery at red lights (49% capacity).