Letters: ‘Grabby’ brakes indicate contanimation

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Q: My 2003 Chevrolet S-10 has a problem with the brakes only when they are cold. During the first few applications of the brakes, the vehicle makes a screeching noise from the tires and comes to a stop quickly like the brakes are locking up. This problem goes away after making about three complete stops. I don’t know what it could be. What do you think? – Ron, Downers Grove

A: Brake friction materials are designed to perform best when they are warm. Cold brakes and overheated brakes actually have a lower coefficient of friction, which leads to longer stopping distances. In your case, though, the cold stopping distances are shorter. This is the result of a higher coefficient of friction – a condition known as “grabbing” brakes. This is generally caused by contaminated brake lining materials.

Even if the brake pads/shoes have sufficient friction material on them, the surfaces could be contaminated with grease or other foreign material. If that’s the case, you’ll not only need to have the brake pads/shoes replaced and the rotors/drums resurfaced or replaced, but you’ll need to find the source of the contamination to prevent it from ruining the new brakes.

Rear drum brakes that have grease on the friction surfaces can be caused by leaky axle seals. In regard to disc brakes, if too much lubricant is applied to the caliper slides, excess lubricant can contaminate the friction surfaces on the brake pads.

Q: I own a 2006 Hyundai Sonata. The problem is that the airbag light stays illuminated. I brought the car back to the dealer, and they told me it would cost me $60 just to run a diagnostic on the car. Is this problem a major concern? Also, is this an expensive repair? – Valerie, Chicago

A: Airbags are safety devices that help prevent serious injuries during a collision. An airbag light that’s staying illuminated after starting the engine indicates a problem in the system. Sometimes the airbags will still work when there’s a problem with the system, and sometimes they will not. It depends on what the problem is.

Also, the cost to repair this depends on what the problem. It could be simple like a blown fuse. It could be due to a poor electrical connection. It could be due to a faulty component, like an airbag, clock spring or airbag control module. Some of these components are expensive to service. If you want to be sure that the airbags will work during a collision, have the system tested and get a written estimate of what it will cost for repairs.

Q: I was following my wife home the other day and she noticed that the headlights in our 2007 Buick Rendezvous were flickering while stopped at traffic lights. What could be causing this? – George, Hinsdale

A: Flickering lights at low engine speeds are usually the result of fluctuations in voltage levels. A service bulletin (No. 05-06-03-003D) was issued to address this concern for 2005-2007 Buick Rendezvous and Terraza, Chevrolet Uplander, Pontiac Aztek and Montana, and Saturn Relay. The fix is to replace the voltage regulator. The dealer has a kit that includes a couple extra protective pieces along with the regulator.

Questions for Ira Siegel? Call the Auto Advisor Hotline at (708) 633-6839 or e-mail ira.siegel.is@gmail.com. Siegel is an automotive instructor and an automotive service excellence-certified master auto technician.