Wheels: Gary B. writes by e-mail:

“I have a 2006 Chevy Silverado 4X4 truck. The brakes quickly fade when I am almost stopped at a stop sign or traffic light. The brake pedal pulsates and sometimes you can hear a loud buzz from the pedal. This problem occurred many times during cold weather.

The truck currently has 36,000 miles on it.

About two years ago I took it to a local dealer, because the front wheels would lock up when the truck was parked overnight in wet weather. They told me I had a bad bearing in the left front wheel and my brake rotors were rusted so badly they had pieces missing. Total for the bearing and brake job was over $900. I later had the same wet weather lock-up, and it was determined the brake pads were swelling up when wet. I was told this was normal.

Some months later the wet weather lockup was so bad that I asked to have the pads replaced and they did so. The sticking problem was gone but on occasion I feel the loss of braking power when slowing to a stop. Thank you”.

Halderman: I think what you are hearing and experiencing is the antilock braking system (ABS) being activated when you are slowing to a stop. The front wheel bearing used on this truck is a sealed unit that contains two rows of ball bearings and a wheel speed sensor all in one assembly. If this bearing assembly wears, the wheel speed sensor cannot detect the speed of the wheel accurately and, as a result, the ABS controller starts to pulse the wheel brake because it “thinks” is is slowing faster than the other wheels. The controller is performing normally, but what is working is the speed signal from the wheel speed sensor.

You stated that one front wheel bearing was replaced. I would suspect that the other front wheel bearing could be the source of your problem. Ask an experienced technician to check the output of the wheel speed sensor to verify improper operation before replacing the front wheel bearing/speed sensor assembly.

James D. Halderman is an ASE-certified master technician. Submit questions to jim@jameshalderman.com or follow him on Twitter @jameshalderman, or write to: Wheels, Marketing Publications Department, Dayton Daily News, 1611 S. Main St., Dayton OH 45409.