Mazda Trucks 1972-1986 Repair Guide

Belts

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See Figures 1, 2, 3, 4 and 5

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Fig. Fig. 1: There are typically 3 types of accessory drive belts found on vehicles today



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Fig. Fig. 2: An example of a healthy drive belt



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Fig. Fig. 3: Deep cracks in this belt will cause flex, building up heat that will eventually lead to belt failure



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Fig. Fig. 4: The cover of this belt is worn, exposing the critical reinforcing cords to excessive wear



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Fig. Fig. 5: Installing too wide a belt can result in serious belt wear and/or breakage

INSPECTION



Inspect the belts for signs of glazing or cracking. A glazed belt will be perfectly smooth from slippage, while a good belt will have a slight texture of fabric visible. Cracks will usually start at the inner edge of the belt and run outward. All worn or damaged drive belts should be replaced immediately. It is best to replace all drive belts at one time, as a preventive maintenance measure, during this service operation.

TENSION CHECKING & ADJUSTING



Fan Belt

See Figures 6, 7, 8, 9, 10, 11 and 12

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Fig. Fig. 6: A gauge is recommended, but you can check belt tension with thumb pressure



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Fig. Fig. 7: Various belt tension adjustments on the diesel engine



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Fig. Fig. 8: Alternator belt tension adjustment



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Fig. Fig. 9: Rotary engine belt tensioning points



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Fig. Fig. 10: Some belts have adjuster pulleys that allow you to tighten and loosen tension simply by turning a screw ...



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Fig. Fig. 11: ... while others require you to pry on them to tighten tension and push on them to loosen



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Fig. Fig. 12: Engine Identification Chart

  1. Apply thumb pressure (about 22 lbs.) to the fan belt midway between the pulleys and check the deflection. It should be approximately 3 / 8 in. for new belts and 1 / 2 in. for used belts.
  2.  
  3. To adjust the tension, loosen the alternator mounting bolt and adjusting bolt.
  4.  
  5. Move the alternator in the direction necessary to loosen or tighten the tension.
  6.  
  7. Tighten the mounting and adjusting bolts and recheck the tension.
  8.  

Thermactor Air Pump Belt

  1. Check the air pump drive belt tension by applying thumb pressure at a point midway between the air pump pulley and the crankshaft pulley. The deflection should be 1 / 2 - 5 / 8 in.
  2.  
  3. If the tension is not correct, loosen the mounting and adjusting bolts slightly.
  4.  
  5. Pry the air pump outward (or inward) until the proper deflection is obtained.
  6.  
  7. Tighten the adjusting and lower bolts to 22 ft. lbs.
  8.  

 
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