Excessive Vacuum Drop Diagnosis

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

If the vacuum continues to drop, remove the pressure and return hose from the pump.
Install the plugs (1,2) supplied with the J 43485 into the pressure and return port.

Fig 1: Installing Plugs Into Power Steering Pump Pressure & Return Ports
Courtesy of GENERAL MOTORS CORP.
Attach the J 43485 to the J 35555 or equivalent.
Place the J 43485 on or in the pump reservoir filler neck.

Fig 2: Bleeding Power Steering System Using J 43485 & J 35555
Courtesy of GENERAL MOTORS CORP.
Apply a vacuum of 68 kPa (20 in Hg) maximum.
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.

IMPORTANT: 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 the pressure hose.
Fluid must be free from discoloration.

Observe the fluid.
If 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
Repeat the bleed procedure from the beginning.
Drive the vehicle approximately 16 km (10 mi) in order to warm the system to operating temperature. Evaluate vehicle on a smooth flat surface.
Verify the following conditions:
- There is smooth power assist.
- The vehicle operates quietly.
- The pump maintains the proper fluid level.
- There is not any leaking in the steering system.
- The fluid is free of foam or discoloration.