Mazda 323/626/929/GLC/MX-6/RX-7 1978-1989




All Models

Belt tension is very important, as a belt that is too tight will put too much stress on the bearings of the components it drives, causing them to wear out prematurely. A belt that is too loose will slip, causing (1) the belt to wear out quickly due to friction heat, and (2) inefficient alternator, air pump, cooling fan or air conditioner operation because much of the turning power supplied by the main drive pulley is lost.

The belts should be inspected and/or adjusted at 2,000 miles (3,221 km) and then every 4,000 miles (6,441 km). First, make sure that the belt is properly positioned in the pulley. Check the pulleys for damage. Inspect the belts for cracks and signs of fraying. These usually develop on the inner surface and extend into the backing or outer surface of the belt. Check also for glazing, a completely smooth appearance which indicates slippage. A belt that is in good shape will have a slightly grainy appearance like cloth. Replace belts that show cracks or glazing.

Check belt tension. Apply pressure with your thumb at the mid-point between two pulleys, and the belt should stretch or deflect about 1 / 4 - 1 / 2 in. (6-13mm). If the belt is too tight or too loose, adjust/replace as necessary.


Except RX-7

See Figures 1, 2 and 3

To adjust belts, first locate the mounting bolt on the air pump or alternator (each has its own belt and adjusts to permit that belt to be tensioned correctly). This bolt attaches the unit to the engine and has a nut on the end. Put a wrench on either end and loosen the bolt until there is practically no tension on it. Then, loosen the adjusting bolt, which is located on the opposite side of the unit and which passes through a slot. Pull the alternator or air pump away from the engine and tighten the adjusting bolt just enough to hold the unit while you check tension. Repeat the adjustment procedure until the belt deflects the proper amount, then fully tighten the adjusting and mounting bolts. Avoid too much belt tension or overtightening of bolts. A new belt should be tensioned just slightly more (about 0.4 in. or 10mm deflection) and checked after several hundred miles of operation to make sure that tension is still adequate. (Tension is lost very rapidly until a new belt is broken in.)

Click image to see an enlarged view

Fig. Fig. 1: Some engines utilize an idler pulley with a locknut at its center

Click image to see an enlarged view

Fig. Fig. 2: After loosening the idler adjuster locknut, turn the adjusting bolt clockwise to increase belt tension or counterclockwise to decrease it

Click image to see an enlarged view

Fig. Fig. 3: On some GLC engines equipped with power steering, the pump pulley uses a slotted adjusting bar, adjusting bolt and locknut to adjust belt tension

Late model GLCs, 323s, 626s, MX-6s and 929s may use an adjusting bolt on either the idler pulley (a pulley which is not directly associated with any of the accessories) or on the power steering pump itself. This bolt makes adjustment much easier because you don't have to hold the accessory under a great deal of tension while tightening the mounting bolts.

On models where the idler pulley has a locknut at its center, simply loosen the locknut, then turn the adjusting bolt clockwise to increase belt tension or counterclockwise to decrease it or remove the belt. Do not forget to retighten the locknut when tension is correct, or vibration may cause it to fall off. Recheck the tension with the locknut tightened and readjust if necessary.

To adjust the power steering pump pulley on the GLC, loosen the slotted adjusting bar bolt, the mounting bolt across from it, and the locknut at the bottom of the adjusting bolt. Turn the adjusting bolt counterclockwise to remove the belt or reduce tension, and clockwise to increase it. When tension is correct, tighten the adjusting bolt locknut, adjusting bar bolt, and pump mounting bolt.

On 626, MX-6 and 929 models with a 4-ridge or 5-ridge ribbed type V-belt driving both the air conditioner and power steering pump, belt tension is much greater. With a used belt, deflection should only be about 1 / 4 in. (6.35mm).


See Figures 4, 5 and 6

The RX-7 may be equipped with as many as three or four separate drive belts. The belts are arranged at the front of the engine and drive the cooling fan/water pump, alternator, power steering pump, emission control air pump and air conditioner compressor (if so equipped).

Click image to see an enlarged view

Fig. Fig. 4: Checking belt tension on 1979-85 RX-7

Check the tension of each belt at the arrows numbered 1, 2, 3 and 4 (depending on year) shown in the illustration. Press on the belt with your thumb using moderate pressure (about 22 lbs.). The belts should give or deflect the amounts shown in the chart.

Click image to see an enlarged view

Fig. Fig. 5: Checking belt tension on 1986-89 RX-7

Click image to see an enlarged view

Fig. Fig. 6: RX-7 belt deflection limits

Use the following appropriate procedure and illustration to make drive belt adjustment(s).


See Figure 7

  1. Slightly loosen the stationary pivot bolt on the alternator or air pump.
  3. Loosen the adjusting bolt.
  5. Using a piece of wood (tool handle, etc.) as a prybar, move the alternator or air pump outward or inward until the proper deflection is obtained.

Click image to see an enlarged view

Fig. Fig. 7: Adjusting alternator drive belt tension on 1986-89 RX-7

When prying on the alternator or air pump, make sure the prybar is anchored against the engine case and not against a component (distributor cap, etc.) which could break.

  1. Tighten the adjusting bolt. Remove the prybar and tighten the pivot bolt.


See Figures 8 and 9

  1. Loosen the locknut on the idler pulley, if so equipped.
  3. Turn the adjusting bolt until the proper tension is reached.

Click image to see an enlarged view

Fig. Fig. 8: Adjusting air conditioning compressor drive belt tension on 1986-89 RX-7

  1. Tighten the locknut and recheck the belt tension.

Click image to see an enlarged view

Fig. Fig. 9: Adjusting power steering pump drive belt tension on 1986-89 RX-7


All Models
  1. Loosen the accessory being driven and move it on its pivot point to free the belt.
  3. Remove the belt. If an idler pulley is used, it is often only necessary to loosen the idler pulley to provide enough slack to remove the belt.

To install:
  1. After the new belt is in place and properly tensioned, start the engine and allow it to run for about five minutes to seat the new belt.
  3. Stop the engine and recheck the belt tension. Adjust as necessary.

On engines with many driven accessories, other belts may have to be removed to access the one being replaced.