Noise caused by the relief valve is normal when the brakes
are applied. Firmly pressing the brake pedal when the vehicle is parked also
causes noise. Air temporarily gets into the fluid when the brakes are
applied.
Hydraulic pump noise can be confused with transmission, rear axle or
generator noise.
Air in the fluid causes noise. Fill and bleed the system when a hose
has been disconnected.
Use the following steps in order to locate and correct the noise problems:
| • | Inspect the fluid level. |
| • | Adjust the fluid level as needed. |
| • | Inspect the hoses at the places where the hoses contact other
vehicle parts. |
| • | Reposition the hoses as needed. |
| • | Inspect the fluid for air. The following conditions may exist
if air is present: |
| - | Extremely noisy operation |
| • | Bleed the brake booster system if air is present. |
| • | Inspect the hydraulic brake booster pump pressure. |
