Bleed the system. Check the vacuum booster
VACUUM POWER BOOSTER
With the transmission in Neutral, stop the engine and apply the parking brake control. Apply the brake pedal several times to exhaust all vacuum in the system. Check hydraulic system for leaks or insufficient fluid.
Apply the brake pedal and hold it in the applied position. Start the engine. If the vacuum system is operating, the brake pedal will tend to move downward under constant foot pressure. If no motion is felt, the power brake booster system is not functioning. Go to next step.
Remove the vacuum booster hose from check valve connection. Manifold vacuum must be available at the check valve end of the vacuum booster hose with the engine at idle speed and the transmission in Neutral. If the manifold vacuum is available to the power brake booster, connect the vacuum booster hose to the power brake booster check valve and repeat steps 1 and 2.
Check and if no downward movement of the brake pedal is felt, install a new power brake booster.
Operate the engine a minimum of 10 seconds at fast idle. Stop the engine, and let the vehicle stand for 10 minutes. Then apply the brake pedal with approximately 20 lbs. Of force. The brake pedal feel should be the same as that noted with the engine operating. If the brake pedal feels hard (no power assist), install a new check valve and retest. If the brake pedal feels spongy, bleed the hydraulic system to remove air. See BLEEDING SEQUENCE.
VACUUM BOOSTER CHECK VALVE
The function of the power brake booster check valve is to allow manifold vacuum to enter the power brake booster and prevent the escape of vacuum in case manifold vacuum is lost during sustained full throttle operation. To test the function of the power brake booster check valve:
Start and run the engine for at least 10 seconds.
Operate the brake pedal to check for power assist.
Disconnect the vacuum booster hose from the power brake booster. Do not remove the power brake booster check valve from the power brake booster.
There should be enough vacuum retained in the power brake booster for at least one more power-assisted brake operation.
VACUUM POWER BOOSTER
Removal & Installation
Remove the brake master cylinder. See MASTER CYLINDER.
Compress the power brake booster hose clamp. Disconnect the power brake booster hose from check valve.
Disconnect the brake booster push rod. See Fig. 23.
Remove the hairpin clip.
Separate the stoplight switch and the brake booster push rod from the brake pedal pin.
Remove the brake booster push rod bushing.
Remove the bulkhead sound insulator. See Fig. 24.
Remove the power brake booster nuts. See Fig. 59. Remove the power brake booster.
To install, reverse removal procedure.
Monday, March 15th, 2010 AT 10:31 AM