Brakes - Vacuum Check Valves Identification

90mitsubishi09 SUBJECT:

POWER BRAKE CHECK VALVE TESTING
NO. TSB-90-35-001

DATE June, 1990

MODEL Galant, Sigma, Mirage
PURPOSE

Two types of power brake vacuum check valves are used on 1989 Galant, Mirage, and Sigma vehicles. The difference between these valves is their location in the power brake booster system. Both types maintain a limited vacuum reserve in the power brake booster. The early type valve is in the end of the power brake booster nipple; the later type is located inside the vacuum hose assembly leading from the intake manifold vacuum connector to the power brake booster. This bulletin provides testing procedures for the later type vacuum check valve located inside the power brake booster vacuum hose.

WARNING: When replacing the power brake booster the correct style hose must be installed. If the old style brake booster vacuum hose (without internal check valve) is installed on the new style power brake booster there will be NO vacuum reserve and this could result in loss of power brake assist.



CHECK VALVE IDENTIFICATION



LATER TYPE CHECK VALVE TESTING PROCEDURE

1. Remove the power brake booster vacuum hose from the vehicle.

2. Using an external vacuum pump, apply vacuum to the booster side of the vacuum hose. If vacuum is held the check valve is good, proceed to step 3. Conversely, if there is no vacuum held the check valve is leaking and the vacuum hose assembly must be replaced.

CAUTION: Do not attempt to remove the check valve from the vacuum hose assembly.



3. Again using the external vacuum pump, apply vacuum to the intake manifold side of the vacuum hose. No vacuum should be held. If there is vacuum the vacuum line of the check valve is plugged and the vacuum hose assembly must be replaced.

CAUTION: Do not attempt to clean the vacuum hose or check valve.