In addition to the specified intervals, the brakes should be inspected every time the wheels are removed or whenever a defect is suspected. Symptoms indicating a potential brake system defect include the vehicle pulling to one side when the brake pedal is depressed, squealing or dragging noises when the brakes are applied, excessive brake pedal travel, pulsating of the pedal, or brake fluid leaks, typically onto the inside of the tire or wheel. Begin by loosening the wheel lug nuts, then raise the vehicle and place it securely on jack stands before removing the wheels. Each caliper contains two pads (an outer and an inner), which are visible with the wheels removed. Check the pad thickness by looking at each end of the caliper and through the inspection window in the caliper body; if the lining material is less than the specified thickness, replace the pads. If it is difficult to determine the exact thickness, remove the caliper(s) and pads for further inspection. Clean the pads with brake cleaner and re-measure them, then measure the disc thickness with a micrometer to ensure it has service life remaining; replace any disc thinner than the specified minimum thickness and check for scoring, gouging, or burned spots. Before installing the wheels, inspect all brake lines and hoses for damage, wear, or leakage, and ensure they are clear of sharp edges and moving parts. All models have rear drum brakes; with the rear wheels removed, ensure the parking brake is off and tap on the outside of the brake drums to loosen them before removing the drums. Clean the brake assemblies and note the thickness of the lining material on both front and rear shoes; if any lining is thinner than specified, replace all brake shoes, especially if they are cracked or soaked with brake fluid. Ensure all brake springs are connected and in good condition, check the wheel cylinders for fluid leakage, and inspect hoses and connections for signs of leakage. Wipe the inside of the brake drums with a clean rag and check for score marks or deep scratches; if imperfections cannot be removed, the drum must be machined. If all parts are in good condition, install the drums, wheels, and lower the vehicle. To check the brake booster, sit in the driver's seat and perform a series of tests: with the brake fully depressed, start the engine and observe if the pedal moves down slightly; with the engine running, depress the brake pedal several times to ensure the travel distance does not change; then, with the engine off, hold the pedal for about 30 seconds to check for sinking or rising. Restart the engine, run it for about a minute, and turn it off, then firmly depress the brake several times to see if the pedal travel decreases with each application; if not, the brake booster has failed. For the parking brake, park the vehicle on a steep hill with the parking brake set and the transmission in Neutral; if the parking brake cannot prevent the vehicle from rolling, it requires attention.
Posted by GMPartsGiant Specialist 
