C Yukon 2WD V8-5.7L VIN R (1999)
Hydraulic Brake Booster: Initial Inspection and Diagnostic Overview
System Tests
The hydraulic booster uses fluid pressure from the power steering system. A malfunctioning power steering system can affect the hydraulic booster. A
malfunctioning booster can affect the steering system. Before beginning extensive testing, perform the following procedure.
1. Check all power steering and brake pipe connections for leaks and restrictions.
NOTICE: Power steering fluid and brake fluid cannot be mixed. If brake seals contact power steering fluid or steering seals contact brake fluid,
seal damage will result.
2. Ensure that the master cylinder is properly filled.
NOTICE: Power steering fluid and brake fluid cannot be mixed. If brake seals contact power steering fluid or steering seals contact brake fluid,
seal damage will result.
3. Ensure that the power steering pump reservoir is properly filled.
If the power steering fluid contains air, refer to Diagnosis of the Power Steering System in Power Steering System.
4. Check the power steering pump belt for wear and improper tension.
5. Check the power steering pump pressure.
Functional Test
1. With the ignition OFF, apply and release the brake pedal several times. This will empty the accumulator.
2. Apply and hold the brake pedal with 180 N (40 lb) of force.
3. Start the engine.
The pedal should fall away, and then push back against your foot.
