What's causing Sean's brakes to smoke?

Dear Car Talk

Dear Car Talk | Dec 01, 2008

Dear Tom and Ray:

I have a four-wheel-drive 2005 Dodge Dakota with 32,000 miles on it. Since I had the front brake pads replaced four months ago, I have noticed a faint burning smell coming from the wheels after I drive to work. I took it back to the repair shop, and they could not find anything wrong. This weekend, I took it down a winding canyon road, and when I got to the bottom, there was smoke coming from the wheels, along with a strong burning smell. I took it to the Dodge dealer, and they can't find anything wrong with the brakes -- nothing charred, no pulsation and plenty of pad left. Do you have any idea why my brakes are smoking? -- Sean

TOM: Well, usually brakes smoke for one of two reasons, Sean. Either they're being applied continually, or someone has offered them a good Cuban stogie.

RAY: Let's assume that you're not resting your foot on the brake pedal while you drive. We have to look at the parts of the brake system that can lead to the brakes staying on when your foot isn't on the pedal.

TOM: One possibility is that your mechanic used some real cheap brake pads, and they're too big for the caliper brackets. That can cause the pads to stay too close to the disc rotors and rub against them. But I'm guessing that when you took the truck to the Dodge dealer, they would have noticed that -- and taken the opportunity to sell you a new set of factory pads.

RAY: The second possibility is that you have a sticking caliper. The caliper is the device that squeezes the brake pads together around the disc rotor. If the caliper doesn't release properly, it'll keep the brakes applied while you drive.

TOM: And calipers can misbehave intermittently, and be hard to "catch in the act." So, if you can narrow the smoking to one particular wheel, it might be worth trying a rebuilt caliper on that wheel to see if that solves the problem.

RAY: On the other hand, you do say in your letter that your brakes -- plural -- were smoking. And it's unlikely that more than one caliper would get sticky at the same time. So if it really is all of the wheels, or at least both front wheels, then I'd go farther up the line, to something that could keep all the brakes applied.

TOM: That would be the power-brake booster. The booster uses vacuum to multiply the force that your foot applies to the brake pedal. When it's failing, it can essentially "stick" in the boost, or "on," position. That means it's applying the brakes when you're not.

RAY: And while that's a nice display of initiative on the part of the brakes, it's not an acceptable state of affairs. So ask your original mechanic to drive the truck for a day or two. If he can make it smoke, he can jump out and test the booster on the spot. Or at the very least, he can narrow it down to a specific wheel or wheels. Good luck, Sean.

Get the Car Talk Newsletter

Got a question about your car?

Ask Someone Who Owns One