GM Full-Size Trucks 1970-1979 Repair Guide

Power Steering Pump

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REMOVAL & INSTALLATION



See Figures 1, 2, 3 and 4



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Fig. Fig. 1: Unfasten the retainers ...



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Fig. Fig. 2: ... then remove the bracket



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Fig. Fig. 3: Remove the power steering pump from the vehicle



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Fig. Fig. 4: View of the power steering pump mounting

  1. Disconnect hoses at pump. When hoses are disconnected, secure ends in raised position to prevent drainage of oil. Cap or tape the ends of the hoses to prevent entrance of dirt.
  2.  

On models with a remote reservoir, disconnect the reservoir hose from the pump and secure in a raised position. Cap the hose pump fittings.

  1. Install two caps at pump fittings to prevent drainage of oil from pump.
  2.  
  3. Loosen bracket-to-pump mounting nuts.
  4.  
  5. Remove pump belt.
  6.  
  7. Remove pump from attaching parts and remove pump from vehicle.
  8.  

To install:
  1. Position pump assembly on vehicle and install attaching parts loosely.
  2.  
  3. Connect and tighten hose fillings.
  4.  
  5. Fill reservoir. Bleed pump by turning pulley backward (counterclockwise as viewed from front) until air bubbles cease to appear.
  6.  
  7. Install the pump belt over the pulley.
  8.  
  9. Bleed the power steering system.
  10.  

BLEEDING



  1. Fill oil reservoir to proper level and let oil remain undisturbed for at least two minutes.
  2.  
  3. Start engine and run only for about two seconds.
  4.  
  5. Add oil if necessary.
  6.  
  7. Repeat above procedure until oil level remains constant after running engine.
  8.  
  9. Raise front end of vehicle so that wheels are off the ground.
  10.  
  11. Increase engine speed to approximately 1500 rpm.
  12.  
  13. Turn the wheels (off ground) right and left, lightly contacting the wheel stops.
  14.  
  15. Add oil if necessary.
  16.  
  17. Lower the vehicle and turn wheels right and left on the ground.
  18.  
  19. Check oil level and refill as required.
  20.  
  21. If oil is extremely foamy, allow vehicle to stand a few minutes with engine off and repeat above procedure.
    1. Check belt tightness and check for a bent or loose pulley. (Pulley should not wobble with engine running).
    2.  
    3. Check to make sure hoses are not touching any other parts of the truck, particularly sheet metal except where design calls for a clamp.
    4.  
    5. Check oil level, filling to proper level if necessary, following operations 1 through 10. This step and Step d are extremely important as low oil level and/or air in the oil are the most frequent causes of objectional pump noise.
    6.  
    7. Check the presence of air in the oil. If air is present, attempt to bleed system as described in operations 1 through 10. If it becomes obvious that the pump will not bleed after a few trials, proceed as outlined under testing.
    8.  

  22.  

TESTING



See Figure 5



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Fig. Fig. 5: Checking the power steering hydraulic system

The following procedure outlines methods to identify and isolate power steering hydraulic circuit difficulties. The test provides means of determining whether power steering system hydraulic parts are actually faulty. This test will result in readings indicating faulty hydraulic operation, and will help to identify the faulty component.

Before performing hydraulic circuit test, carefully check belt tension, fluid level and condition of driving pulley.

Engine must be at normal operating temperature. Inflate front tires to correct pressure. All tests are made with engine idling. Check idle adjustment and, if necessary, adjust engine idle speed to correct specifications and proceed as follows:

  1. With engine NOT running disconnect pressure hose from pump and install Tool J-5176 using a spare pressure hose between gauge and pump. Gage must be between shut-off valve and pump. Open shut-off valve.
  2.  
  3. Remove filler cap from pump reservoir and check fluid level. Fill pump reservoir to full mark on dipstick. Start engine and, momentarily holding steering wheel against stop, check connections at Tool J-5176 for leakage.
  4.  
  5. Bleed the system.
  6.  
  7. Insert thermometer (Tool J-5421) in reservoir filler opening. Move steering wheel from stop to stop several times until thermometer indicates that hydraulic fluid in reservoir has reached temperature of 150-170 degrees F.
  8.  


WARNING
To prevent scrubbing flat spots on tires, do not turn steering wheel more than five times without rolling vehicle to change tire-to-floor contact area.

  1. Start engine and check fluid level adding any fluid if required. When engine is at normal operating temperature, the initial pressure read on the gauge (valve open) should be in the 80-125 psi range. Should this pressure be in excess of 200 psi, check the hoses for restrictions and the poppet valve for proper assembly.
  2.  
  3. Close gate valve fully 3 times. Record the highest pressure attained each time.
    1. If the pressures recorded are within specification and the range of readings are within 50 psi, the pump is functioning properly.
    2.  
    3. If the pressures recorded are high, but do not repeat with 50 psi, the flow controlling valve is sticking. Remove the valve, clean it and remove any burrs using crocus cloth or fine home. If the system contains some dirt, flush it. If it is exceptionally dirty, both the pump and the gear must be completely disassembled, cleaned, flushed and reassembled before further usage.
    4.  
    5. If the pressures recorded are constant, but more than 100 psi, below the low listed spec., replace the flow control valve and recheck. If the pressures are still low, replace the rotating group in the pump.
    6.  

  4.  
  5. If the pump checks within specifications, leave the valve open and turn (or have turned) the steering wheel into both corners. Record the highest pressures and compare with the maximum pump pressures recorded. If this pressure cannot be built in either (or one) side of the gear, the gear is leaking internally and must be disassembled and repaired.
  6.  
  7. Shut off engine, remove testing gauge, spare hose, reconnect pressure hose, check fluid level and/or make needed repairs.
  8.  

 
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