Run-run-run sound coming from rear

Probably rear hub bearings. You want Timken HA590373 or Toyota OEM as the cheap versions will fail quickly. They have abs sensors built in and can be difficult to remove diy.

 

If it sounds like it's coming from inside the passenger compartment, it could be the HV battery cooling fan. It's designed to speed up and slow down in tune with car speed, so that the driver won't hear it. It's air intake is in the right rear.

 

The fuel pump is under the rear driver's side seat area as well.

Posted via the PriusChat mobile app.

 

How does that correlate with this statement that he made:

I think it probably doesn't.

 

Wheel bearing rumble is common on these cars as they age. Any experienced mechanic can recognize the sound. Replacement quality is important as cheap units fail in months.

Simple tests. On a downhill at 35mph let off on the gas to shutoff the engine. The wheel bearings will continue to rumble, a fuel pump will shutoff.

For the battery fan hook up your fan control app and shut it off at 35mph. A wheel bearing rumble will continue. The fan will quit. Another test is to simply turn the battery fan to high while parked so you know what it sounds like.

Finally jack up the rear and give the rear wheels a hard rotate. A bad wheel bearing will often make a low buzzing sound, a good one will be quiet. The wheel should rotate about three turns, a bad bearing will stop in one or less. Realize these direct tests are unloaded. A wheel bearing under load transmits vibrations through the suspension into the body creating the rumble.

 

does it happen in ev and hv?

 

You'll need a module which connects to the car's OBD port (the app talks to that).

 

Dr Prius is probably the easiest to use app that allows you to turn up the battery blower. It requires a bluetooth obd2 module to interface to the car. You can also use it to monitor the battery temperature which could cause the battery blower to operate on high speed. It is also useful to review the hv (high voltage) battery voltages. There are several apps besides Dr Prius.

I can tell you you can't hear the battery fan even on high unless the ac blower is less than half speed and you are not moving. Even then it sounds like a muffled blower. You would never mistake it for a wheel bearing that is easy to hear driving at 35-45 mph with the engine and ac on. Same goes for the fuel pump.

A Prius hybrid, unless it is a plug in version, rarely runs on ev alone. It is constantly switching the gas engine on and off depending on the power required. At a stop the gas engine goes off. Going downhill or letting off the accelerator will turn the gas engine off. Most of the time you are getting some electric power and gas engine power combined.

But everyone hopes for the easiest solution even if it does not make sense under the conditions described. In any case, the bluetooth obd2 module or similar linked below comes in handy for other purposes.

 

that would be a first

 

The tire would also lose pressure.


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that might cause a run-run-run sound

 

I suppose it could be tread separation. How old are your tires? When were they last rotated?

 

Start from easy to hard. The way I'd go about it is as follows...

1) Go to the rear tires and visually inspect to make sure nothing looks suspect (tread low, bubbles on sidewall, over/underinflated)
2) Jack up the car in the read and spin the rear wheels by hand to ensure they rotate freely and don't make noise

Those 2 alone should help you isolate wether it's the tires or something inside. Say those checks pass...

3) Do the rj test, go up to speed with all blower accessories off, lift of the gas completely so the little EV symbol on the dash lights up. If it does and the sound is heard it's time to revisit the tires

4) rj test passed, find out when the sound comes on. If you can sometimes get up to speed and not hear the sound it might be the hybrid battery fan

5) So the sound comes on constantly, check the fan blower behind the glove compartment, make sure nothing has made it's way through the filter into the blower

That's all I got for now unfortunately.

 

Its the rear wheel bearings

 

If OP is at all handy I believe they're bolt on which are easy to change.

 

They are bolt on but often air hammered off as there is a press fit center piece housing the abs sensor that rust welds.



Possible Solution used by one member

 

That double wrench setup is brilliant.