Sable V6-183 3.0L DOHC VIN S MFI (1997)
Vacuum Brake Booster: Testing and Inspection
NOTE: Refer to Brakes/Traction Control See: Testing and Inspection/Initial Inspection and Diagnostic Overview Pre-Checks before begining
diagnosis.
PRE-CHECKS
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 brake booster for damage.
BRAKE BOOSTER OPERATION CHECK
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Check the hydraulic brake system for leaks or low fluid.
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With transaxle in "PARK", stop engine and apply parking brake. Apply the brake pedal several times to exhaust all vacuum in the system.
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With the engine turned "OFF" and all vacuum in the system exhausted, apply the brake pedal, and hold it down. "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 brake booster
vacuum system is not functioning.
BRAKE BOOSTER TESTING
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Remove the vacuum hose from the power brake booster. Manifold vacuum should be available at the brake booster end of the hose with the engine
at "IDLE" speed and the transaxle in "PARK" or "NEUTRAL". Make sure all unused vacuum outlets, are properly capped, hose connectors are
properly secured and all 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 Operation Check Step 3. If no downward movement of the brake pedal is felt,
replace the power brake booster.
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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 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.
