Unlike gasoline engines, diesel engines have little vacuum available to power brake booster systems. The diesel is thus equipped with a vacuum pump, which is driven by a single belt off of the alternator. This pump is located on the top right side of the engine.
Some are also equipped with a low vacuum indicator switch which actuates the BRAKE warning lamp when available vacuum is below a certain level. The switch senses vacuum through a fitting in the vacuum manifold that intercepts the vacuum flow from the pump. The low vacuum switch is mounted on the left side of the engine compartment, adjacent to the vacuum pump.
The vacuum pump cannot be disassembled. It is only serviced as a unit (the pulley is separate).
REMOVAL & INSTALLATION
See Figure 1
- Remove the hose clamp and disconnect the pump from the hose on the manifold vacuum outlet fitting.
- Loosen the vacuum pump adjustment bolt and the pivot bolt. Slide the pump downward and remove the drive belt from the pulley.
- Remove the pivot and adjustment bolts and the bolts retaining the pump to the adjustment plate. Remove the vacuum pump and adjustment plate.
- Install the pump-to-adjustment plate bolts and tighten to 14-19 ft. lbs. (19-26 Nm). Position the pump and plate on the vacuum pump bracket and loosely install the pivot and adjustment bolts.
- Connect the hose from the manifold vacuum outlet fitting to the pump and install the hose clamp.
- Install the drive belt on the pulley. Place a 3 / 8 in. drive breaker bar or ratchet into the slot on the vacuum pump adjustment plate. Lift up on the assembly until the proper belt tension is obtained. Tighten the pivot and adjustment bolts to 11-18 ft. lbs. (15-24 Nm).
- Start the engine and make sure the brake system functions properly.
The BRAKE light will glow until brake vacuum builds up to the normal level.1995-96 Models
See Figure 2
- Remove the air cleaner and drive belt.
- Partially drain the coolant and remove the upper radiator hose.
- Disengage the coolant reservoir hose from the radiator and support.
- Remove the fan blade clutch and shroud.
- Remove the vacuum pump pulley using pulley removal tool T69L-10300-B or equivalent.
- Loosen the pump retainers, disengage the hoses and remove the pump.
- Connect the hoses to the pump, install the pump and tighten the bolts to 18-23 ft. lbs. (24-31 Nm).
- Install pump pulley using tool T65P-3A733-C or equivalent.
- Install the fan shroud, clutch and fan.
- Connect the cool reservoir hose and radiator hose to the radiator.
- Refill the cooling system and install the drive belt.
- Install the air cleaner assembly.