Rumble/growl from front

Start with easy stuff: Look for broken and loose plastic splash shields--there are several large pieces under the front bumper and fenders. Rotate tires. When the front wheels are off, check brake calibers, rotors, axles, wheel bearings, ball joints and bushings. Look for leaks and stains and loose/torn things.

How long have you had the car? Has it ever been in an accident?

 

My front wheel bearings went at 45,000, the steering wrack at 60,000, yours at the moment needs bearings, check the wrack.

 

I have a 2005 prius with 360k kms and I had been following a slow car near Oberon NSW Australia and approached a steep hill with a passing lane. A hyundai SUV following me indicated he wanted to pass us both presumably as I was a little car and deserved to be passed. I gunned the prius and was doing 110kph at the top of the hill with him some 10 car lengths behind. I then backed off as I was in a 100 zone and he passed me doing some 130 kph and I never saw him again. The prius then commenced growling on overrun. I was travelling to Mt Victoria to pick up a friend of my wife and on the return trip (50KM) the trouble light flared and the prius tripped the cruise control. It was unfortunate as my wife's friend was regaling me with a tale of travelling with the husband of another friend and the car gave the trouble light. They ignored it and shortly the engine blew up. I propped and sat there thinking what would be prudent and decided to finish the trip slowly. I safely reached home (Oberon) and attached the Intelligent Tester which said POA2B which means "Drive Motor A temperature sensor range" which means MG2 temperature beyond limits, or the drive motor is over temperature. We then did a trip to Bathurst with the IT monitoring MG2 temperature and the temperature rose to 160 deg C after about 40KM at 80 kph and the trouble light flared. My diagnosis is that we have a shorted turn (standard electric motor fault) in the main motor (electric) which becomes intolerable at high frequency or high speed. On stopping the temperature dropped to 80 deg C in about 5 minutes. Toyota tells me that there is no value in repairing the electric motor, the whole transmission has to be changed. We have since travelled to Sydney (160KM) and the last 40KM was at 65 kph to keep the temperature below 150 deg C.

 

Bob mills again and we ran the vehicle for a further four months, 40km trips only, then it flashed an earth fault. We reset the DTC (P0AA6, hybrid battery isolation) and headed for home at 60k. At 10ks it alarmed again and we ignored it. After another 2k it ground noisily to a halt, fortunately allowing us enough time to get off the road. We had the following DTCs;
POA78; drive motor A inverter performance. 287 overcurrent.
POA2B; Drive Motor A temperature sensor circuit.
POA2C; Drive motor A ground short in motor A temperature circuit.
P0AA6; Hybrid battery isoolation 526 Not listed..
We tilt trayed it home and it made a pronounced clicking noise in neutral as it dragged onto the tilt tray.
Next morning we reset the DTCs and tried to select drive.. The trouble light came up and we got POA78. I have ordered a second hand transmission, 80k, at $A 880 from Melbourne. Manhandling it into my shed in neutral has flattened the main battery which is a puzzle.

 

Aranthon: Did you ever find out that the problem was?

I have a 2010 Prius with 128K miles. It is making a rumbling sound (as if I'm rolling over rumble strips in the road) from the left side. I notice the sound when going 5-30mph. Thinking it might be a bad wheel bearing, I jacked up the car and tried to see if there was any free play by pressing on the wheel left-right, then up-down. There was no free play (that I could feel) from either left front or left rear tire. Has anyone experienced this sound before?

 

@StingRay did you ever figure out what it was?

I am getting the same thing, it occurs really bad if I turn the wheel slightly to the right. 2008 Prius with 230k. Before this it would make a slight rubbing sound and then last night it change to sound like driving over rumble strips.

The only other thing to note is every day when the car is cold I get a low growl until things warm up. Service department said this might be rust forming on the rotors… starting to thing there are two issues not connected but unsure. I’ve been dealing with this a few months but it just got worse. Thanks in advance!

 

Your description certainly sounds like a bad wheel bearing. I usually don't find much looseness or rock in the wheel until it gets really bad. One way to confirm is to jack the front of the car and safely support on jackstands. Start the car, disable traction control, then have an assistant put it in drive and slowly bring the speed up - 40 to 50 mph.

You can hear the bad (front) bearing as it spins- a mechani's contact stethoscope helps. Another trick is to CAREFULLY reach over the top of the spinning tire and feel the coil spring. Often the bad bearing will make that spring vibrate lots more than the other side.

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That procedure scares me and I'm fearless.

 

Just another day on the job.

Or you pay a bloke to do it for you.

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Be prepared to be boggled.
Tracking down bad wheel bearings can be a real bear.
I had 3 different independent professional mechanics, including a dealership, steer me wrong on mine a couple years ago.
They replaced the wrong wheelbearings twice.
In the end it took me a year to solve it....and I mean ME solve it, because the pro's kept missing the problem.
Bad bearings don't always follow the stereotypical warning signs that mechanics tell you about.
It may take some hunting, and in the end, replacing the bearing that everyone swears is NOT being the problem....
Sometimes, the bad bearing doesn't sound bad unless it is under load on the road, so just putting it up on jackstands and running the wheels with a steth or screwdriver listening does always work.
It may cost you less to replace all four yourself, than to pay a pro to do it, and then have him do another, because he replaced the wrong ones.