Excessive Vacuum Drop Diagnosis

Tools Required: 

• J 35555  Mity Vac
• J 43485  Power Steering Bleed Adapter

1. If the vacuum continues to drop, remove the pressure hose and the return hose from the pump.
2. Install the plugs (1,2) supplied with J 43485  into the pressure and the return port.
   Fig 1: Plugs To Pressure And Return Ports

   Courtesy of GENERAL MOTORS CORP.
3. Attach J 43485  to J 35555  or equivalent.
4. Place J 43485  on or in the pump reservoir filler neck.
5. Apply a vacuum of 68 kPa (20 in Hg) maximum.
6. If the vacuum drops again, repair or replace the pump. If the vacuum holds steady, continue to check the other parts of the steering system.
   NOTE: Fluid must be free from bubbles and foam. Be aware of periodic bubbles that indicate a loose connection or leaking O-ring seal in the return hose or in the pressure hose. Fluid must be free from discoloration.
7. Observe the fluid.
8. If the condition persists, replace the following parts:
   • The return hose clamps
   • The return hose O-rings
   • The pressure hose O-rings
   • The gear cylinder line O-rings
   • The reservoir to pump O-ring
9. Repeat the bleed procedure from the beginning.
10. Drive the vehicle approximately 16 km (10 ml) in order to warm the system to operating temperature. Evaluate the vehicle on a smooth flat surface.
11. Verify the following conditions:
    • The power assist is smooth.
    • The vehicle operates quietly.
    • The pump maintains the proper fluid level.
    • The steering system does not leak.
    • The fluid is free of foam or discoloration.
    Fig 2: Bleeding Power Steering System
    Courtesy of GENERAL MOTORS CORP.