Chrysler Full-Size Trucks 1989-1996 Repair Guide

Diesel Engine Vacuum Pump

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See Figure 1

Unlike gasoline engines, diesel engines have little vacuum available to power brake booster systems. Although models with the Cummins diesel engine are also equipped with a dual-diaphragm brake booster, a separate vacuum pump assembly provides the vacuum necessary for booster operation.

The vacuum pump assembly consists of a housing and twin vacuum pumps. The vacuum pump and power steering pump are combined to form a single assembly. Both pumps are operated by a drive gear attached to the steering pump shaft. The drive gear is operated by the camshaft gear.



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Fig. Fig. 1: Details of the diesel engine brake booster twin vacuum pumps

REMOVAL & INSTALLATION



See Figures 2 and 3

  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the booster vacuum hose at the upper pump.
  4.  
  5. Disconnect the fluid lines at the power steering pump. Cap the lines to prevent dirt contamination or loss of fluid during service.
  6.  
  7. Remove the bolts attaching the dual pump assembly to the engine block and remove the assembly.
  8.  
  9. Drain the fluid from the steering pump reservoir. At this point, the vacuum pump can be separated from the steering pump assembly.
  10.  



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Fig. Fig. 2: The stud nuts must be removed to separate the vacuum pump housing from the power steering pump

  1. Remove the old gasket material from the pump mounting surface of the engine block.
  2.  



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Fig. Fig. 3: Exploded view of the diesel engine vacuum pump assembly

To install:
  1. Install the vacuum hoses on the vacuum pumps, if removed.
  2.  
  3. Position a new gasket on the pump assembly. Hold the gasket in place with non-hardening sealer.
  4.  
  5. Align and install the dual pump assembly on the engine. Install and tighten the attaching bolts to 57 ft. lbs. (77 Nm).
  6.  
  7. Connect the fluid lines to the steering pump. Tighten the pressure line fitting to 40 ft. lbs. (55 Nm). Make sure the return line and clamp are properly positioned and secured on the pump return tube.
  8.  
  9. Attach the booster hose to the upper vacuum pump and attach the interconnecting hose to each pump.
  10.  
  11. Fill the power steering pump reservoir with new fluid.
  12.  
  13. Connect the negative battery cable.
  14.  
  15. Start and run the engine. Slowly turn the steering wheel left and right to circulate fluid and purge air from the system. Recheck the fluid level and top off, if necessary.
  16.  
  17. Verify that the booster is providing power assist and a firm brake pedal is attained before moving the vehicle.
  18.  

 
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