For the past few weeks, I’ve noticed am occasional humming noise while driving. It seems to happen more frequently at lower speeds (around 15-30 mph, though it has also happened at around 45 mph), and it stops as soon as I apply the break. Turning the A/C on and off does not appear to have an effect, nor does opening/closing the windows (in case the humming noise was just air at a certain vibration), nor does the radio.
I took it to a mechanic, but it didn’t happen when he drove it around the block, so he said that it’s probably due to tire pressure imbalance, adjusted the pressures, and told me to bring it back if it happens again.
Does anyone have any idea what this is, or what other things I should look for?
Pressing the brake pedal to make it go away can be indicative of it being brake related. It could mean your brake pads’ alarm tab is rubbing against the rotor. That usually means that the pads have to be replaced soon.
Did your mechanic check the brakes?
Well, I know the brake pads are at least somewhat worn, because it takes longer to brake than when I’m driving a new car (I have to press down harder with my foot). That’s why I also asked him if the brake pads need to be replaced. But he said (as he drove it around) that he doesn’t think they need to be replaced just yet.
However, what you are suggesting would make sense as far as timing: I got the car last year, it’s a 2005 model, I have no idea when the brake pads were last changed, I’ve been thinking about the brakes for some time, and this noise is fairly new. I’m not sure whether he actually inspected the brake pads to determine how much they were worn.
It’s hard to say based upon your description. It could be you are hearing the brake pad wear indicator. There’s a gadget on the brakes that is intended to make an obnoxious noise when the pads are wearing thin. Your noise might be from that, and it is only now just starting but will become worse as the pads wear more. If so, you’ll be money ahead to address it now, before the pads wear out and the rotors are ruined. The only way way to tell if the brake pads are worn is to take the wheel off and measure them. Did your mechanic do that? If not, that’s the first thing to try.
Another possibility is a wheel bearing starting to go on the fritz. Usually drivers report wheel bearing noise as a growl that gets louder the faster you go. But applying the brakes can sometimes affect wheel bearing noise, especially if it is just starting, so its something to consider. There’s other causes too, like CV joints in need of a lube can sometimes make this kind of noise. I expect your mechanic’s philosophy – and maybe this is what is best in terms of your wallet – is that maybe indeed there is a problem, but it will be easier to diagnose when the problem gets worse. Best of luck.