Mazda Trucks 1972-1986 Repair Guide

Timing Gears and Gear Case

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The correct installation and adjustment of the camshaft drive gears is mandatory if the engine is to run properly. The camshaft controls the opening of the engine valves through coordination of the movement of the crankshaft and camshaft. When any given piston is on the intake stroke the corresponding intake valve must open to admit air/fuel mixture into the cylinder. When the same piston is on the compression and power strokes, both valves in that cylinder must be closed. When the piston is on the exhaust stroke, the exhaust valve for that cylinder must be open. If the opening and closing of the valves is not coordinated with the movements of the pistons, the engine will run very poorly, if at all.

REMOVAL & INSTALLATION Diesel Engine



See Figures 1, 2, 3, 4 and 5

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Fig. Fig. 1: To remove the timing gears on the diesel engine requires a bolt-on and claw type pullerinset shows a claw type puller removing the crankshaft gear



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Fig. Fig. 2: View of the timing gear alignment on the diesel engine. To avoid confusion, note that the left idler gear has one set of double marks and one single mark, while the right idler gear has two sets of single marks and one set of double marksall gears are installed with the marks facing outward



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Fig. Fig. 3: Removing the camshaft gear using a puller on the diesel engine



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Fig. Fig. 4: Removing the injection pump gear using a puller on the diesel engine



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Fig. Fig. 5: Using a special tool to install a new timing gear cover seal on the diesel engine

  1. Rotate the engine so that no. 1 piston is on TDC of its firing stroke.
  2.  
  3. Disconnect the battery ground.
  4.  
  5. Drain the cooling system.
  6.  


CAUTION
When draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

  1. Remove the fan and fan shroud.
  2.  
  3. Remove all drive belts from the engine.
  4.  
  5. Remove the power steering pump and its bracket, and position it out of the way, without disconnecting the hoses.
  6.  
  7. Remove the water pump.
  8.  
  9. Remove the crankshaft pulley bolt and, using a puller, remove the pulley.
  10.  

Unbolt and remove the timing gear cover. Discard the gasket. The front cover seal may be replaced at this time. Coat the outer circumference of the new seal with sealer, and the sealing surface with clean engine oil.

  1. Remove the oil pan.
  2.  
  3. Make sure that all timing marks are aligned as illustrated. If not, rotate the engine to align them.
  4.  
  5. Remove the bolts from the camshaft gear, and remove the washer and friction gear.
  6.  
  7. Remove the bolts from the injection pump gear, and remove the washer and friction gear.
  8.  
  9. Using a puller, remove the camshaft, crankshaft and injection pump gears.
  10.  
  11. Matchmark the idler gears for installation reference and remove the nuts and gears.
  12.  
  13. Support the injection pump and remove the nuts attaching it to the timing gear case. Support the pump in this position for the rest of the procedure.
  14.  
  15. Remove the bolts attaching the gear case to the block and remove the case.
  16.  
  17. Discard all old gaskets and thoroughly clean the gasket mating surfaces.
  18.  
  19. Check all gears for wear and chipping. Replace any suspect parts.
  20.  

To install:
  1. Replace the front cover seal at this time.
  2.  
  3. Using a new gasket, coated with sealer, install the gear case. Torque the bolts to 12-17 ft. lbs.
  4.  
  5. Aligning all timing marks, as shown in the accompanying illustration, install the gears in the following order:
    1. Crankshaft and Right Idler
    2.  
    3. Camshaft
    4.  
    5. Left Idler
    6.  
    7. Injection Pump
    8.  
    9. All friction Gears and Washers
    10.  

  6.  
  7. Install all the nuts and bolts on the gears. Observe the following torques:

    Camshaft gear, 45-50 ft. lbs.
     
    Idler gears, 17-23 ft. lbs.
     
    Injection pump gear, 40-50 ft. lbs.
     

  8.  
  9. Using a new gasket coated with sealer, install the timing gear cover. Torque the bolts to 12-17 ft. lbs.
  10.  
  11. Install the oil pan.
  12.  
  13. Install the crankshaft pulley.
  14.  
  15. Install the water pump.
  16.  
  17. Install the power steering pump.
  18.  
  19. Install the accessorydrive belts.
  20.  
  21. Install the fan and fan shroud.
  22.  
  23. Fill the cooling system.
  24.  
  25. Connect the battery ground.
  26.  

 
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