Do-It-Yourself Disk Brake Replacement on a GMC Safari AWDby Jule Pamplin
For twenty years, the GMC Safari was the longest-running line of rear-wheel-drive minivans. In 1990, GM began making the Safari with optional all-wheel drive. The all-wheel models have four disk brakes versus the rear-wheel model that came with rear drum brakes. Every Safari was engineered to exceed the safety standards for stopping distance set by the National Highway Traffic Safety Administration. The disk brake pads need regular maintenance to uphold those standards.
Preparing to Replace the Brakes.
Before you attempt to replace the Safari's brakes, it is important to set up a work space that will make the replacement easier and safer. Park the Safari in an area that will allow you to work on both sides of the vehicle. This area should be away from passing traffic, relatively flat and dry, and away from the curb. Put the transmission in park, apply the parking brake and place tire blocks behind the wheels opposite the wheels you will be working on first, to prevent the Safari from rolling.
Accessing the Braking Assembly.
While people tend to change both of the front brakes and then the rear brakes, a better order of replacement for a larger vehicle such as the Safari is one side (front and rear) and then the other. Loosen the lug nuts on both wheels of the side you choose to change first, with the socket on the tire iron. Lift the Safari with the lifting jack. Place the jack beneath the frame under the side skirts. Do not put the jack under the panelling, as it is not strong enough to support the weight of the vehicle during lifting. Once the Safari has been lifted, place jack stands beneath the frame. Two stands, one near the front tire and one toward the rear, will be the minimum needed. To be certain of a stable base from which to work, place one jack stand each beneath the frame at the ends of the vehicle, and one in the middle. Make sure the Safari's tires have at least one inch of clearance between the tires and the road surface. Remove the lug nuts and pull the wheels from the lug nut bolts.
Replacing the Brake Pads
With the wheels removed, you will have an unobstructed view of the entire outer braking assembly. The polished metal disk is the rotor. Surrounding approximately one-fourth of the rotor is the caliper. Within the caliper are the brake pads and the caliper piston. Use a 13 millimeter socket and ratchet to remove the caliper bolts. There are two caliper bolts, both located on the side of the caliper facing away from you. Beside the top caliper bolt is another bolt on the brake fluid bleed valve. You will need to open the bleed valve to allow the fluid to drip from the caliper piston before installing the new pads. Place a drip pan beneath the brakes to catch the expelled fluid. Open the bleed valve with an adjustable wrench. Two full turns will open the valve sufficiently. Pull the caliper from the rotor. The pads will be attached to the caliper sides by metal clips that slide from the caliper. If the brakes are rusted, spray WD-40 or chain lubricant on the metal clips. Spray one brake and then the other. By the time you return to the first brake, the lubricant will have had enough time to be effective. Slide the pads from the caliper sides. To make room for the new, bulkier pads, you will need to open the caliper piston. The piston is a rubber-coated ring that protrudes from the inside of one of the caliper sides. Squeeze the piston against the side of the caliper with vise-grip pliers or a C-clamp. While you are forcing the piston open, brake fluid will be forced out and into the drip pan below. Place the new brake pads onto the caliper. Replace the caliper over the rotor. Place the caliper bolts in their openings and tighten them with a 13-millimeter socket and ratchet. Close the brake fluid bleed valve with an adjustable wrench Replace the wheels onto the lug nut bolts and screw on the lug nuts by hand. Lift the Safari with the lifting jack, remove the jack stands, and return the vehicle to the ground. Tighten the lug nuts with the tire iron.
Returning the Piston to the Proper Position
The caliper piston needed to be opened to accommodate the new pads. The piston will need to be returned to a point that makes immediate braking possible. To return the piston to the proper position, press the brake pedal repeatedly. The first few depressions of the brake pedal will offer little resistance. As you continue to press the pedal, the fluid will be returned to the caliper, pushing the piston against the brake pads. When the piston is in the correct position, the pedal response will feel normal (a little stiffer than the last time you pressed the brake pedal before the brake pad replacement).
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