Replacement of Master Cylinders in 1997 Chevy S10 Pickups

At the heart of the 1997 S10s braking system is the master cylinder, a manually operated hydraulic pump. Just like a heart, the master cylinder pumps fluid through small channels. Instead of forcing blood through veins, the master cylinder presses hydraulic DOT 3 brake fluid through the S10s brake lines, creating the pressure needed to push the brake pads and shoes against their respective rotors or drums to stop the truck. Replacing the master cylinder is a simple task, but the required bleeding processes are slightly more difficult.

Instructions

Pull the lid from the master cylinder and siphon out as much of the brake fluid from the master cylinder as you can, using a clean turkey baster. Transfer this fluid to a small, sealable container.

Position a small drain pan under the master cylinder to catch any fluid and loosen the brakeline-to-master cylinder fittings, using a line wrench. Pull the lines from the master cylinder and allow all the fluid to drain from the lines and the master cylinder into the drain pan.

Wrap a clean, lint-free cloth around the open end of each brake line to avoid contaminating the fluid remaining in the lines.

Remove the two nuts securing the master cylinder to the brake booster, using a ratchet and socket, and pull the master cylinder from the brake booster.

Position the new master cylinder into a soft-jawed bench vise with the front of the master cylinder tilting downward slightly. Thread the master cylinder port plugs into the master cylinder ports, then tighten them with a ratchet and socket. Fill the master cylinder to the Max line with fresh DOT 3 brake fluid.

Press the plunger on the rear of the master cylinder inward about an inch and release it several times, using a wooden dowel, until the plunger no longer travels an inch.

Reposition the master cylinder in the vise with the front of the master cylinder tilted upward and repeat step 2.

Move the master cylinder in the vise so it is in a level position and place a drain pan under the master cylinder. Loosen the front plug on the master cylinder and press the master cylinders plunger inward until it stops, then tighten the plug. Allow the plunger to return to its normal position. Repeat this step on the rear plug.

Slide the new O-ring, if not already installed, onto the rear of the master cylinder until it seats into its groove.

Position the master cylinder onto its mounting studs on the brake booster and hand-thread its retaining nuts. Tighten the master cylinder nuts to 27 foot-pounds with a torque wrench and socket. .

Remove the plug from the front line port on the master cylinder, using a ratchet and socket. Quickly insert the brake line into this port and thread its fitting by hand. Tighten the brake line fitting to 20 foot-pounds with a torque wrench and crowfoot attachment. Repeat this step to install the rear brake line.

Fill the master cylinder to the Max line with new DOT 3 brake fluid.

Raise the rear of the S10 with a floor jack and slide jack stands under the trucks rear axle tube. Lower the S10 onto the jack stands.

Crawl under the vehicle, so you are behind the right-rear wheel. Find the bleeder valve the 1/4-inch metal valve at the top of the rear drum brake backing plate or on the rear of the brake caliper, depending on the truck's rear brake system.

Press a 1/4-inch-diameter rubber hose onto the bleeder valve and set the other end of the hose in a clean, clear container. Pour new DOT 3 brake fluid into the clean, clean container until the fluid submerges the end of the rubber hose.

Instruct your assistant to press the brake pedal to the floor slowly and hold it. Turn the bleeder valve a half-turn counterclockwise, using a combination wrench, to open it and watch the submerged end of the rubber hose for air bubbles. Tighten the bleeder valve and instruct your assistant to release the brake pedal. Repeat this step until no air bubbles come from the end of the hose, but wait 15 seconds between tests. On the final tightening of the bleeder valve, torque the bleeder valve to 62 inch-pounds, using an inch-pound torque wrench and crowfoot attachment.

Refill the master cylinder to the Max line with fresh DOT 3 brake fluid.

Repeat steps 3 through 6 on the left-rear wheel.

Raise the rear of the truck off the jack stands, using a floor jack, and remove the jack stands. Lower the rear of the S10 to the ground.

Lift the front of the truck off the ground with a floor jack and position jack stands under its frame rails. Lower the truck onto the jack stands.

Bleed the S10s right-front wheel then the left-front wheels using the process outlined in steps 3 through 6.

Raise the front of the truck off the jack stands with a floor jack and remove the jack stands. Lower the S10 to the ground.

Press the lid back onto the master cylinder until it clicks into place.