My brakes sound like barking seals.

Dear Car Talk

Dear Car Talk | Dec 01, 1998

Dear Tom and Ray:

My front brakes, which are just a few months old, make a very strange noise --
on occasion. These "occasions" are never when I drive to the dealer or the
mechanic. I've had mechanics drive with me, and the noise never occurs for them.
There is no pattern to when it will make the noise -- not wet pavement, not hot
or cold temperatures, not hard braking. Nothing I can figure out.

The sound: The closest I have been able to describe it is the sound of a seal
barking. And it does this in a rhythm with the rotation of the wheels, slowing
as the car stops. It is very loud and very scary. But the car stops fine, and
the guys who have driven it have taken off the wheels and say there's nothing
wrong with the brakes. They have no idea what the noise is. Do you? -- Ken

TOM: A seal barking, eh? Aruuu! Aruuuu! Well, we have seen a few rare cases in
the shop in which a beached seal has taken up residence in the vicinity of the
front axle. But since you don't live near the ocean, Ken, we can probably rule
that out.

RAY: Assuming that your mechanic has also ruled out the potentially dangerous
front-end components (wheel bearings, ball joints, etc.), then I'd put my money
on a brake disc or brake drum that's warping (you don't say what kind of car you
own, so I don't know what kind of brakes you have). The fact that the noise
occurs at the same speed as the spinning wheels means that a brake pad is
scraping something each time the wheel comes around. And what it's scraping is
the raised (or warped) part of the disc or drum.

TOM: So why does it happen intermittently? It probably has to do with
temperature. As the disc or drum heats up, it subtly changes shape. And during a
certain part of that "change process," you get the noise. Before it hits that
"right" temperature, the brakes are fine. No warping, no pulsing, no screeching,
no growling, no barking. Then you get into that zone where the noise occurs. And
then, as the brakes continue to heat up, the disc continues to change shape and
the noise disappears again.

RAY: The bad news is it's almost impossible to figure out exactly which
component in your brake system is causing this problem. And unless you can
narrow it down to a specific wheel, you'd have to replace virtually every disc,
drum and pad to make the noise go away.

TOM: The good news is that you can safely ignore the noise. Since the mechanics
have physically inspected the front end (we assume) and the brakes, and have
determined that the calipers are free and the slides are not seized, you can be
quite sure that this is not a safety problem.

RAY: So that leaves you two practical options, Ken. Spend $600 replacing your
brakes. Or spend $600 on a phenomenally good stereo system for the car, and then
turn it up whenever the noise occurs. I know what I'd do.

* * *

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