Power Brake Booster: Notes

Check all vacuum hoses and connections. All unused vacuum connectors should be capped. Hoses and their connections should be correctly secured and in good condition with no holes or collapsed areas. Check the vacuum hose between the power brake booster and power brake booster check valve, as well as the vacuum hose between the engine and power brake booster check valve, for damage. Check and test the power brake booster check valve for damage. See CHECK VALVE  .

1. Check the hydraulic brake system for leaks or insufficient fluid.
2. With the transaxle in PARK or NEUTRAL, and the engine in OFF, apply the parking brake. Depress the brake pedal 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 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. Manifold vacuum should be available at the booster end of the hose with the engine at idle speed and the transaxle in Neutral. Ensure that all unused vacuum outlets are correctly secured and that vacuum hoses are in good condition. Repair as necessary. 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, install a new 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, and then depress the brake pedal with approximately 20 lbs. of force. The brake pedal feel (brake application) should be the same as that noted with the engine operating. If the brake pedal feels hard (no power assist), check and test the power brake booster check valve. If necessary, install a new power brake booster check valve and then repeat this test step. If brake pedal still feels hard, install a new power brake booster. If brake pedal movement feels spongy, bleed the hydraulic system to remove air from the system.
6. Run engine at fast idle for 10 seconds or longer. Press the brake pedal and listen for noise(s). If the power brake booster is noisy, install a new power brake booster.