GM 15870511 Power Brake Vacuum Booster

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Remove your foot from the brake pedal once the engine is turned off, then test if there are any changes in the distance it travels. Push down on the pedal and turn on the engine to observe if it takes a slight drop. Air tightness check: Start the engine and allow it run for one to two minutes before turning it off. With your foot gently on the brake pedal, press slowly down several times, ensuring that you note whether there is an immediate drop during initial depression but after subsequent depressions rises gradually. While holding for 30 seconds, press the brake pedal while the engine is running and shut off the engine. Removal and installation: Turn ignition key to OFF position and depress brake pedal several times to deplete vacuum in power assist booster. Apply parking brake and loosen lug nuts on left front wheel.Raise left front of vehicle and support securely with jack stands.Remove left front wheel.Remove upper engine cover. Remove air filter housing.Remove all ABS hydraulic control unit mounting bracket fasteners and carefully slide unit aside.Unbolt master cylinder from power booster.On V8 models as well as 2004-2008 V6 models remove exhaust crossover pipe from between manifolds.On 2009 up V6 engines drain cooling system; remove heater pipes which go under throttle body.Detach check valve then electrical connector if equipped from power brake booster.Pull out brake pedal position sensor.Remove retaining clip holding booster pushrod to brake pedal arm.In engine compartment, remove mounting bolts for coolant pipe brackets on V8 engine models.Inside vehicle, remove pushrod from brake pedal arm.Turn booster counterclockwise until free of its mount.Carefully slide booster assembly out from under hood.Installation is reverse of removal making sure booster retaining tang fully engages into its bracket at firewall base while tang at base of booster firmly engages bracket on firewall.Put in new retaining clip securing push rod coming out of brake booster to arm of brake pedal.Tighten master cylinder mounting fasteners. Carry out a full functional test of the brakes before returning vehicle to normal service.

The first step is to depress the brake pedal several times with the engine off and ensure there is no change in pedal reserve distance.