Brake Calipers May Be Whining for Some Grease

Dear Car Talk:

I recently purchased a 2013 Toyota RAV4 LE. After a few days of in-town driving, it began to make a high-pitched whining sound from the back end -- definitely not coming from inside the car.

It doesn't happen reliably, though when it does, it tends to begin after I've been on the road for 20 minutes or so. When I brake, the noise stops, then begins again when I let off the brake. Hitting a pothole once also made it stop mid-whine.

Another thing I noticed is that the sound doesn't happen when the roads are wet, though this could be just coincidence. It's anybody's guess when it may happen, which has made it hard to convince my mechanic that it's happening at all!

I'm hoping you, in all your wisdom, can tell me what it is. Thank you! -- Charmon

It sounds like you may have a sticky brake caliper, Charmon. When you step on the brake pedal, the caliper squeezes the brake pads around the brake rotor -- slowing the wheel.
If the caliper is old and sticky, though, it may not release quickly, or completely. So even though you'd taken your foot off the brake pedal, the pads may still be touching the rotor a little bit. And when the pads are just barely touching the rotor, they tend to vibrate, and that's the noise.

If you move them one way or the other -- either press the pads harder against the rotor, or move them fully away, the noise will stop. That's why stepping on the brakes brings a temporary quiet. When you hit the pothole, it probably jolted the caliper to release the pads. And when it's raining, the water acts like a lubricant and prevents the pads from vibrating and making noise.

So, it all makes sense, Charmon. Ask your mechanic to check both rear calipers. I think at least one is sticking and needs to be cleaned and greased. And get it done before it binds up completely and chews up your pads and rotor, too.

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