GM Service Manual Online
For 1990-2009 cars only

With the engine running at idle and the shift lever in NEUTRAL (N), depress the brake pedal and hold a constant foot pressure on the pedal. If the pedal gradually falls away with the constant pressure, the hydraulic system may be leaking. Visually check the following to confirm a suspected leak.

    • Master Cylinder Fluid Levels. While a slight drop in the levels occurs with normal lining wear, an abnormally low level resulting in the illumination of the BRAKE warning lamp may indicate a leak in the system. The system may be leaking internally or externally. (The system may appear to pass this test, but still have a slight leakage.)
    • Brake Hose and Pipe Connections. If leakage is found, verify the torque of the fasteners and/or replace the hose or the pipe.
    • Connecting Brake Components. Inspect fro damage, rebuild or replace as needed.
    • Caliper. If leakage is found, rebuild or replace the assembly.
    • Also, check the service brake pedal travel, brake adjustment and the parking brake adjustment.