How to Change a Brake Check Valve on a 94 Jeep Wrangler

Chrysler Jeep has produced the Wrangler version of its famous off-road vehicle since 1987. The 1994 Wrangler has the YJ designation and is available with either an inline four cylinder or inline six cylinder engine. The hydraulic system is separated into two circuits to maintain braking capability if a brake line leaks in one circuit. The master cylinder has a reservoir for each circuit. A sensor in the check valve assembly signals a warning light if one or the other circuit fails. The check valve or proportioning valve balances front and rear braking in sudden stops and contains a sensor and switch to warn of failure of a hydraulic circuit.

Instructions

Locate the combination or check valve under the master cylinder. Position a plastic container under the valve to catch brake fluid and be sure to cover all painted surfaces under and around the valve with plastic or newspapers in case some brake fluid spills.

Loosen and disconnect the hydraulic lines from the valve using a wrench. Immediately plug the lines with plastic bags to prevent dirt or other contaminants entering they hydraulic system.

Pull the electrical connector from the front of the valve body. This is the pressure differential switch.

Loosen and remove the bolt that attaches the valve to the mounting bracket. Remove the valve from the engine compartment.

Position the valve in place on the mounting bracket and install and tighten the mounting bolts with a wrench.

Attach the electrical connector to the pressure differential switch.

Attach the hydraulic lines to the valve body and tighten with a wrench.

Apply the brakes several times with the engine off to get rid of any residual vacuum in the lines.

Pull back the clips on the master cylinder and remove the cover. Fill the cylinder with brake fluid and put the cover back on and do up the clips.

Loosen the lug nuts on all four wheels with a lug wrench. Raise the vehicle up with a jack and lower onto jack stands. Finish removing the lug nuts on all four wheels and remove the wheels.

Loosen the bleeder valve slightly on the right rear wheel then tighten it so it is just snug. Put the rubber tube on the end of the bleeder valve and put the open end of the tube in the plastic container. Make sure there is a half inch or so of brake fluid in the container. Get an assistant to pump the brakes several times then hold the brake pedal down. Open the bleeder valve just slightly and observe the fluid running out the tube. Air bubbles should come out of the tube with the fluid. When the fluid slows down close off the valve with a wrench. Tighten the bleeder valve.

Go to the left rear wheel and repeat the bleeding procedure, watching for air bubbles and closing the valve again when the fluid and air bubbles stop coming out. Go next to the right front wheel and finish with the left front wheel. Check the fluid in the master cylinder each time and top it up as required with brake fluid. At the end of this operation the brake pedal should feel solid, not squishy or spongy.