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.
- 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.
- 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.
- Ensure that the power steering pump
reservoir is properly filled.
If the power steering fluid contains air, refer to
Power Steering System Test
.
- Check the power steering pump belt for wear and improper tension.
Refer to
Belt Squeal
.
- Check the power steering pump pressure. Refer to
Power Steering System Test
.
Noise from the relief valve is normal when applying the
brakes. Firmly applying the brake pedal while the vehicle is parked also causes
noise. The noises are the result of air allowed into the fluid during these
conditions. The air remains in the fluid only temporarily.
Power steering pump noise can be confused with transmission, rear axle,
or generator noise.
The following noises come from the hydraulic booster. The noises may
be cause for a customer complaint. Noises may be normal and temporary. Noises
may be a sign of wear, or evidence of air in the hydraulic booster or power
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. The moan may be caused by insufficient power steering
fluid or air in the fluid. Holding the steering wheel turned as far as
possible in one direction holds the power steering pump at relief pressure.
Holding the pump at relief pressure for more than 5 seconds causes
air to enter the system. Verify the cause of the noise using the following
procedure. |
| 1. | Check the fluid level. Fill as needed. |
| 3. | Allow the vehicle to sit for 1 hour. Any air in the system
will escape. |
| 4. | Verify that the moan is no longer present. If the moan persists,
refer to Diagnosis of the Power Steering System in Power Steering System. |
| • | You may hear a high-speed fluid noise when fully applying the
brake pedal. The noise is normal. |
| • | You may notice a slight hiss while the accumulator pressure is
in use. This is hydraulic fluid escaping through the accumulator valve. The
noise is normal. |
| • | If the accumulator is empty when the engine is started, a hissing
noise may be heard during the first brake application or steering maneuver.
The noise is fluid rushing through the accumulator charging orifice. The
noise is normal. The noise should be heard only once after the accumulator
is emptied. |
| | If the noise continues, even though no apparent accumulator pressure
assist occurred, the noise may indicate that the accumulator is not holding
pressure. Check the accumulator. Refer to
Accumulator Leak-Down Test
. |
