Constant hum while moving. I've ruled out the engine. I can hear it while rolling slowly in neutral. The odd thing is that it stops if I'm turning left. What should I be looking at?
2008? Wheel bearings is my suspicion. Pretty easy to check, get the wheels off the ground and grab at 9-3 o'clock and check for movement...and same at 12-6.
Why do wheel bearings hum? They forgot the words.., Lots of Toyota wheel bearings will make noise without getting loose. Generally they get louder up to 45 mph when road noise drowns them out. Typically if the humming decreases when turning left it will be the right passenger side. A Toyota mechanic now on his own Why do customers cry after buying low cost bearings? Because they fail quickly, often within a year.
the 205k mile Prius I recently bought got that issue but it was really worst because the wheel bearings are grinding (not humming) The grinding creates a lot of vibrations inside the cabin and difficult to pinpoint if turning left or right makes a difference. What I did was jack up the front wheels and turn them manually. Then I tried comparing by feel which is noisy (or rough) I bought a pair of wheel hubs and did the right side (passenger) and noise is gone after install. I just keep the other wheel hub for future use (driver side is still ok) In my case the wheel wiggle test (9-3 o'clock) didn't show anything, it's still solid.
A good trick to be able to roll down you windows and listen for various sounds is to drive behind a big, brick business, like a department store building (we have a Khols that's perfect for this.). The sound reflects nicely off the brick and even loud enough to get a video recording so you can have your mechanic listen to it. (Because we all know cars DON'T misbehave when a mechanic is there....little brats!)
