How to Replace Brakes on a 1998 GMC Sierraby Justin CuplerUpdated November 07, 2017
Items you will need
Small, clean container
New wheel bearings
New wheel bearing seals
Bearing seal driver
Multipurpose automotive grease
New cotter pins
In 1962, General Motors changed the name of Chevrolet and GMC pickups to C- and K-series. The C-series indicated two-wheel drive and the K-series indicated four-wheel drive. In 1975, the names of the trim levels on GMC trucks changed to Sierra, Sierra Grande, High Sierra and Sierra Classic with the Sierra trim level being the base level GMC C-K pickup. In 1999, the Sierra name became the model name of the GMC pickup, as GM phased out the C-K nomenclature altogether. The 1998 C-1500 Sierra came standard with a 4.3-liter V-6 engine that produced 200 horsepower; it also came standard with front disc brakes. Replacing the brakes on the 1998 GMC Sierra is a relatively easy task.
Open the Sierra's hood and remove approximately half of the fluid from the brake master cylinder using a turkey baster. Place this fluid in a clean container for reuse.
Loosen the front lug nuts with a ratchet and socket, but don't remove them yet.
Raise the front of the 1998 Sierra with a floor jack and place jack stands under the frame rails. Lower the GMC until only the jack stands support it. Remove the lug nuts and pull the wheels from the truck.
Remove the two guide bolts from the rear of the brake caliper and pull the caliper from the torque plate -- the metal bracket the caliper bolts to -- using a ratchet and socket. Hang the caliper from the coil spring using a bungee cord to prevent damage to the brake hose.
Disengage the spring retainer on the rear of the outer brake pad, by prying upward on the spring with a flat-head screwdriver and pulling the pad from the caliper.
Place an 8-inch C-clamp over the caliper so the screw portion touches the inner brake pad and the fixed part touches the rear of the caliper. Tighten the C-clamp to compress the inner caliper piston. Loosen and remove the C-clamp from the caliper once the C-clamp stops moving.
Grasp the inner brake pad and pull it from the caliper, notice a small retaining spring that holds it in place inside the caliper piston.
Close the jaws of the micrometer and press the "Reset" button to calibrate it. Measure the thickness of the rotor's disc in four places and make a note of the thickest and thinnest measurements.
Compare the thinnest measurement of the rotor to the minimal machining specification of 1.230 inches on a 11.57-by-1.25 inch and 12.5-by-1.26-inch rotor and 1.480 inches on all other rotor sizes. If the rotor measures at or above this specification and has imperfections -- grooves, uneven wear or a mirror-like shine -- remove the rotor and have it resurfaced.
Replace the rotor if it is thinner than the specification indicated in Step 9 and requires resurfacing. Replacement is also required if the rotor is thinner than the measurement stamped on it, which is known as the discard specification, regardless of its condition.
Leave the rotor in place if it has no imperfections and is thicker than the discard specification.
Remove the rotor, as needed, by prying the metal cap from the center of the rotor. Pull the cotter pin from the spindle -- the shaft in the center of the rotor -- with needle nose pliers and remove the castle-shaped nut and washer from the spindle with a ratchet and socket. Pull the rotor toward you and from the spindle.
Pull the bearing from the front-center of the rotor with your finger. Flip the rotor over and remove the bearing seal from the rear-center of the rotor, by prying it with a flat-head screwdriver. Pull the inner bearing from under the bearing seal with your finger. Inspect the bearings for looseness or wear by placing your fingers through the center, like the spindle would and shaking the outer part of the bearing. A loose or worn bearing has a small amount of free play back and forth and makes a slight clicking noise when shaken. Replace loose bearings with new ones.
Discard or have the rotor resurfaced as needed based on the determination made in Step 9.
Pack the new or old bearings, by placing a liberal amount of multipurpose automotive grease in your palm and rotate the bearings in your hand until they are full of grease.
Place the inner bearing into the rear of the new or resurfaced rotor with the tapered end going in first. Place a new bearing seal on top of the inner bearing and seat the seal, by placing a bearing seal driver on the seal and tapping the driver with a hammer.
Slide the rotor on the GMC's spindle and place the outer bearing, tapered end first, into the hole in the center of the rotor.
Reinstall the washer and nut on the spindle and tighten the nut, while spinning the rotor, to 12 foot-pounds with a torque wrench and socket to seat the bearing. Loosen the spindle nut and tighten it to only hand-tight. Place a new cotter pin through the castle nut and through the hole in the spindle. Bend the cotter pins legs in opposite directions to lock it into place, using needle-nose pliers.
Place the inner brake pad in the caliper so the metal clip on the rear of the pad slides into the caliper piston. Press the brake pad until it sits flat against the caliper body.
Clean the caliper bolts with a wire brush, if rusted, and apply a coat of multipurpose automotive grease onto the bolts. Sit the caliper back onto the torque plate and tighten the caliper bolts to 37 foot-pounds with a torque wrench and socket.
Repeat Steps 4 through 18 for the brakes on the other side of the GMC.
Reinstall the front wheels on the GMC Sierra and hand-tighten the lug nuts.
Raise the truck from the jack stands, with a floor jack, and pull the jack stands from under the GMC. Lower the Sierra to the ground. Tighten the lug nuts, in a crossing pattern, to 125 foot-pounds on all Sierras except the 3500 and 162 foot-pounds on the Sierra 3500 with a torque wrench and a socket.
Check the fluid level in the master cylinder. Add fluid from the small container to the master cylinder until the level reaches the "Max" line. Dispose of any unused brake fluid in the small container properly, most auto parts stores discard fluid free of charge.
Press and release the brake pedal until it feels firm. This extends the caliper pistons out so they contact the brake pads.
Please note, steps 10 through 16 are only needed if the rotor must be removed for resurfacing or replacement. These steps may be skipped if the rotor is in acceptable condition.
Never use any thread coating on the caliper bolts, such as thread-lock of antiseize.
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