Component Tests

Brake Booster Functional Test

Vacuum Booster

Inspect all hoses and connections. All unused vacuum connectors should be capped. Hoses and their connections should be properly secured and in good condition with no holes and no collapsed areas. Inspect check valve on the power unit for damage.

Brake Booster Operation Check

1. Check the hydraulic brake system for leaks or insufficient fluid.

2. With transmission in PARK, stop engine and apply parking brake. Depress the brake pedal (2455) several times to exhaust all vacuum in the system.

3. With the engine turned off and all vacuum in the system exhausted, depress 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 vacuum booster system is not functioning.

4. Remove the vacuum hose from the power brake booster (2005) . Manifold vacuum should be available at the check valve end of the hose with the engine at idle speed and the transmission in NEUTRAL. Ensure that all unused vacuum outlets are properly capped, hose connectors are properly secured, and vacuum hoses are in good condition.

   When it is established that manifold vacuum is available to the power brake booster , connect the vacuum hose to the power brake booster and repeat Step 3. If no downward movement of the brake pedal is felt, replace the power brake booster .

5. Operate the engine a minimum of 10 seconds at fast idle. Stop the engine, and let the vehicle stand for 10 minutes. Then, depress the brake pedal with approximately 89N (20 lb) of force. The pedal feel (brake application) should be the same as that noted with the engine operating. If the brake pedal feels hard (no power assist), replace the check valve, then repeat the test. If brake pedal still feels hard, replace the power brake booster .

   If the brake pedal movement feels spongy, bleed the hydraulic system to remove air from the system. Refer to Section 06-06.