Washing your brakes is harmless -- but probably won't silence the squeaks

Dear Tom and Ray:

My daughter-in-law just sent her son out to wash her car's brakes. I told her I had never heard of that before. She said that when her brakes start to squeak, she gets her son to wash the accumulated dust out and they stop squeaking. She said she learned this from her dad. She said you can see the water coming out black for a while, then when the water comes out clear, the dust is gone. Is this for real?
--Marie

Ray: We've never heard of this either, Marie. But starting tomorrow, we're offering a $75 brake-hosing special at the garage.

Tom: What she's having her kid do can't really hurt the brakes, unless it's done while the brakes are hot. Then the cold water could warp the rotors. So you want to make sure the brakes have been sitting for at least an hour before turning a hose on them.

Ray: But otherwise, it's a harmless exercise. The brakes are designed to shed rain and road water. I'm just not sure it's doing much good.

Tom: Right. You can put the hose on the outside of the wheel and rinse off any loose dust on that side of the brakes. But it would be very hard to get to the other side (the inboard side) of the brakes. So you'd never clean more than half of them.

Ray: I'm not aware of small amounts of brake dust being a cause of brake squeal. Normally, when someone comes into our shop with squeaking brakes, we remove the rotors and all the pads, and deglaze everything with an abrasive. But who knows? Maybe the hose is doing a much more rudimentary version of that.

Tom: And if it works, why not?

Ray: Personally, I think she's just getting her son out of the house for half an hour so she can have some peace and quiet. Have you ever heard her tell him that it's time to go out and wax the mailbox?

(Car Talk is a nationally syndicated column by automotive experts (and brothers) Tom and Ray Magliozzi. Write to them at the Car Talk Web site.)