Hydraulic Booster System Test
The hydraulic booster system works with fluid pressure from the power
steering system. Therefore, a malfunctioning power steering system can affect
the hydraulic booster, just as a malfunctioning hydraulic booster can affect
the power steering system. Before extensive testing, make the following checks:
- Check all power steering and brake pipe connections for leaks
or restrictions. NOTICE: Power steering fluid. . .damage will result.
- Make sure the master cylinder is filled with brake fluid.
- Make sure the reservoir of the power steering pump is filled with
power steering fluid.
| • | If the power steering fluid contains air, refer to Bleeding the
Hydraulic System in Power Steering. |
- Make sure the belt on the power steering pump is in good condition.
Refer to [??????]
- Check the pressure of the power steering pump. Refer to Power
Steering System Test in Power Steering.
Noise Diagnosis
The following noises are associated with the hydraulic booster and may
or may not be cause for a customer complaint. Some noises are normal and temporary
in nature. Other noises can be a sign of wear or of air in the booster system
or steering system.
| • | A moan or low-frequency hum (usually accompanied by a vibration
in the brake pedal or steering column) may be noticed during parking or other
low speed maneuvers. This can be caused by a low level of power steering fluid
or by air in the fluid. Holding the pump at relief pressure (steering wheel
held fully to the right or fully to the left) for more than 5 seconds causes
air to enter the system. Check the fluid level and fill as needed. Let the
system sit for 1 hour with the engine off to remove the air. If the condition
persists, refer to Power Steering System Test in Power Steering for further
diagnosis. |
| • | A high-speed fluid noise may be heard when the brake pedal is
fully applied. This condition is normal. |
| • | A slight hiss may be noticed when the accumulator pressure is
used. This is the sound of the hydraulic fluid escaping through the accumulator
valve. This condition is normal. |
| • | If the accumulator is empty when the engine is started, another
hissing sound may be heard during the first application of brakes or the first
steering maneuver. This is caused by fluid rushing through the orifice that
charges the accumulator. It is normal and should only be heard once after
the accumulator is emptied. If this sound continues, even though no apparent
pressure assist was made by the accumulator, it could be an indication that
the accumulator is not holding pressure. Refer to Leakdown Test for the Hydraulic
Booster Accumulator. |
