My brakes are smokin'!

Dear Car Talk

Dear Car Talk | Jun 01, 1999

Dear Tom and Ray:

I have a '94 Honda Accord station wagon. Last year, I stalled because the brake pedal became hard and slowed the car to where I couldn't keep driving. While waiting
for a tow, the brake pedal came back to normal. It happened again recently, and this time smoke was coming out of the brake. The mechanic told me it's the caliper.
Another mechanic told me there is no problem with my caliper. Again, the car returned to normal after two hours. What do you think is wrong? -- Tito

RAY: Well, if mechanic No. 2 actually inspected the calipers and determined that the slides and pistons are all moving freely and easily, then he's probably right -- it's
unlikely to be a caliper problem.

TOM: Plus, a bad caliper won't make the pedal get hard.

RAY: So I'd suspect the power-brake booster. The booster is a device that provides the "boost" or "power" to your power brakes. It multiplies the effort of your foot on
the brake pedal and applies that force to the piston of the master cylinder.

TOM: If the booster is faulty, it could provide pressure to the brakes even when your foot is off the pedal. The result would be that it would seem like you were stepping
on the brakes even when you weren't.

RAY: Here's how you test it. Next time you experience this condition, pull over and yank your Sears 16,598-piece tool kit out of the trunk. Or, alternatively, grab a pair
of Vise-Grips. Unbolt the brake master cylinder from the booster. If brake pressure is immediately released and the car moves freely, then your problem IS the booster.

TOM: If separating the booster from the master cylinder does not solve the problem, then you may have a faulty master cylinder.

RAY: But assuming your mechanic has accurately inspected the caliper, I'd put money on the booster, Tito.

Get the Car Talk Newsletter

Got a question about your car?

Ask Someone Who Owns One