Hi ssfloyd. Welcome to the forum. If you have rear disc brakes, suspect a combination of a warped rotor and grooves worn in the knuckle the caliper and pads mount on. The warped rotor will make the caliper slide harmlessly back and forth on the mount once per wheel revolution and the pads will catch on the grooves worn into the sliding surfaces. They will make a snapping noise when they are forced to pop out of the grooves. The noise could get worse as the brakes heat up due to the rotor warping more when hot.
Once the noise starts to occur, raise the vehicle off the ground and run it in gear. The noise should continue. The are two ways to verify this problem. Remove the wheel, reinstall the lug nuts, and spin the rotor by hand with a dial indicator placed against the braking surface of the rotor. There should be no more than.002" or.003" of runout. Anything more you might be able to see by just watching the rotor and caliper.
The second method involves the use of a tool called the "Chassis Ear". It is a receiver and set of six microphones. A lot of mechanics have never heard of it but it is standard equipment at Chrysler dealerships and most likely many others. Clip one of the microphones right to the caliper and drive the car. You might be able to find this tool at the parts stores, otherwise check the guys who drive the tool trucks like Mac, Matco, Cornwell, and Snapon. From Mac Tools, it is item number ET6600 and costs $199.99 for the older version with six wired microphones. There is a newer model with four wireless microphones and two with wires.
If you have drum brakes on the rear, remove the drum and look for shiny spots in the inside. On some designs it is possible for the parking brake actuator lever to twist a little until it hits raised areas on the drum. This isn't common but then again, neither is a noise.
Tuesday, May 11th, 2010 AT 1:37 PM