K 1500 Truck 4WD V8-5.7L VIN R (1997)
Hydraulic Brake Booster: Component Tests and General Diagnostics
Fluid Level Inspection
When servicing any part of the brake system, check the level in the power steering fluid reservoir. The fluid level in the reservoir should be checked at
regular intervals and added as needed.
Belt Tension
When servicing any part of the brake system, check the power steering pump belt tension and condition. The serpentine belt is not adjustable. Refer to
Engine Drive Belts, Mounts, Brackets and Accessories.
Pipes, Hoses, and Fittings
All pipes, hoses, and fittings should be inspected for leaks at regular intervals. The fittings must be tight and all clips, clamps, and unions supporting the
pipes and hoses must be in place and properly secured. Make sure all hoses and tubes are installed so they do not contact parts of the vehicle that could
cause chafing or wear on the hoses.
Check for leaks by wiping the suspected area clean. Leaking fluid can be easily spotted when the suspected area is clean. When fluid leaks appear,
tighten, repair, or replace nearby fittings and bolts.
Preliminary Tests
The hydraulic booster system works with fluid pressure from the power steering system. Therefore, a malfunctioning power steering system can affect
the booster, just as a booster malfunction can affect the steering system. Before extensive testing, the following checks must be made:
1. Check all the power steering and brake pipe connections for leaks or restrictions.
CAUTION: 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. Check and fill the master cylinder with brake fluid.
3. Check and fill the power steering pump reservoir with power steering fluid. If the power steering fluid contains air, refer to Steering and
Suspension for further diagnosis.
4. Check the power steering pump belt for wear and insufficient tension.
5. Check power steering pump pressure.
Functional Test
With the ignition switch in the "OFF" position, apply the brake pedal several times to empty the accumulator. Apply the brake pedal using 180 N (40 lb)
of force and start the engine. The pedal should fall away and then push back against your foot.
Accumulator Leakdown Test
1. Start the engine and charge the accumulator by applying the brake pedal or turning the steering wheel from stop to stop.
2. Turn the engine off and let the vehicle sit for one hour.
3. After one hour there should be at least two power assisted applications with the engine off.
4. If the accumulator will not hold a charge for one hour, but functions normally after charging, the accumulator valves are faulty.
^ To repair this condition, the booster must be disassembled and the accumulator valves replaced. Refer to Hydraulic Booster Service and Repair.
5. If the accumulator can be heard charging and discharging but does not hold a charge, the accumulator valves are faulty.
^ To repair this condition, the booster must be disassembled and the accumulator valves replaced. Refer to Hydraulic Booster Service and Repair.
6. Empty the accumulator by pressing the brake pedal several times.
7. If the accumulator has lost its gas charge, the accumulator "can" will rotate or wobble. Repairing this requires replacing the accumulator assembly.
