narrowing down a strange sound

Well I would expect the first thing to do is to get that red light investigated and to tell the mechanic about the strange noise. One of the problems with strange noises on a Prius is that they are built in - it even mentions them in the manual. I think the ones that they are referring to are for the re-charging system - but that isn't on all the time.

 

+1 on the red light. I think maintenance light is yellow, not red. Red warning lights are reserved for serious problems.

 

Just have to mention that the front wheel bearings make that sort of sound, as it's speed related they come first to mind.
A free OBD2 read at pep boys or an auto parts dealer will tell you about the red light code, Toyota dealer won't be free.
And welcome to prius chat

 

My 06' bearings went between 45 and 60k, obd2 is the on board diagnostics system, you can pick up a consumer obd2 reader or as many on pc do a scanguage2 which allows you to customize up to 4 different values and reads and resets trouble codes.
Might be worthwhile to have a competent mechanic do a test drive and or check for bearing noise.

 

If it's just the yellow maintenance light then I won't waste time or money trying to read trouble codes - there is none. The light can be turned off following instructions in the owner's manual. Do keep us updated on the noise issue. One of the member here had wheel bearing going bad while still under warranty.

 

how many miles on the tires? how does the tread look? you could be right about pumping up the pressure. let it back out and see if the noise goes away. if it's a bearing and it seizes up, you're stuck. you probably have quite a while though. jack it up and spin the front tires to see if there is any friction sound or feeling. all the best and welcome to p/c!

 

My 2006 just started making this sound at 65,000 miles. Naturally, it started while I was outbound on a 1,500 mile trip, so I had to worry about it the whole way. On the other hand, it gave me a lot of time to experiment. Here is what I found:

1) The sound is a turbine-like whining coming low from the front, most likely on the driver's side (left side). It is mechanical, as it sometimes includes a rumble that can be felt. It is definitely not inverter whine.

2) The sound varies directly with wheel speed. Speeds around 60 mph appear to generate a resonance that intensifies the sound. I don't hear it at all below 20 mph, but it may simply be too faint to hear.

3) The sound is the same with our without power: shifting to N causes no change.

4) Engine RPM freely changes without affecting the sound.

5) Hard turns to the left at speed reduce or eliminate the sound. These are turns fast enough to generate noticeable lateral force.

6) There are no warning lights or other indications of trouble. Mileage remains normal.

Conclusions:

From these symptoms I surmise that the bearings are going on the front driver's side. Presumably the left turns change the bearing loading and suppress the sound.

I will make an appointment at the dealer this week. Expect a follow-up post.

One more interesting observation: After driving 1,200 miles with a funny noise, it's amazing to see how many strange symptoms I noticed (imagined) just because I was looking for trouble. Even with my fairly extensive knowledge of the Prius, I borrowed trouble at every available opportunity. The placebo effect lives, even among technical experts.

Tom

 

I'd agree with the bearing guess. It kind of makes one long for the day when bearings had zerks - in stead of being sealed. It's one of those imponderables - how some of us have hundreds of thousand of miles on the Prius with no bearing issues ... while others ....

Nope . . . you'd think so, but it aint so. For example, our Lexus hybrid lets you know it's time to change the cabin filter with a red triangle. What ever gets programmed into the maintenance schedule get the same thing.

 

Fixed. Just as suspected, the strange sound was coming from the driver's side wheel bearing. As described by the Toyota tech: "Your left front hub assembly has failed." The whole unit is replaced as an assembly. It took about two hours and cost $526; $106 for the part, $380 for labor, and the rest miscellaneous charges and tax.

The tech said that they have replace "quite a few" of these. Mine went out at 67,000 miles.

Edit: I mistyped the mileage, which I have corrected to 67,000 miles, not 37,000. Incidentally, this is the first repair on my Prius.

Tom

 

Tom describes my event also and my front driver's bearing went out also at
30,000 miles. It was replaced under warranty.

The tip off is a change in sound when turned. Just drive down an empty road and whip the car around a little like your driving around a sudden obstacle.
But not that fast. Just enough to put a turning load on the car.

 

The failure of one side is not an indication that the other is about to fail. In other words, the service life of these hub assemblies seems to be highly variable. Some people get 150,000 miles out of them, some have them die young.

Additionally, there really isn't a time or cost savings in replacing both sides at the same time, other than the convenience of one trip to the dealer.

Tom