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Repla­cing a Drive Belt

Belt Types
  • V‑type — Sits in the deep v‑shaped groove of the pul­ley wheel, con­tact­ing the sides of the groove
  • Ser­pent­ine – Flat with a num­ber of grooves run­ning length­wise which run in reverse of the grooves on the out­er edge of the pul­ley wheel. The grooves increase the con­tact sur­face area to pre­vent the belt from slip­ping as it rotates.
Pro­ced­ure

Step 1 — Loosen ten­sion and remove belt

Loc­ate the adjust­ment fasten­er and loosen it. This is usu­ally on the altern­at­or mount­ing or on a sep­ar­ate pul­ley wheel. Move the adjust­ing mech­an­ism in far enough to allow you to remove the belt. Some vehicles use an auto­mat­ic spring ten­sion sys­tem. In that case, pull the ten­sion­ing device back so that you can remove the belt.

Step 2 – Inspect drive and drive pul­leys

Check the drive and pul­ley wheels. Look for cracks and oth­er forms of dam­age. Check that there is no side­ways move­ment indic­at­ing worn bear­ings, and spin the pul­ley wheels by hand to check that the bear­ings are rotat­ing freely.

Step 3 – Select cor­rect replace­ment belt

Obtain the cor­rect size and type of replace­ment belt spe­cified in the manu­al, and com­pare it with the belt you have just removed. They should be very sim­il­ar, although the old belt may have stretched in use.

Step 4 – Install V‑belt

Install the new belt, mak­ing sure that it is prop­erly seated in the V‑shape groove.

If the belt is a Ser­pent­ine type, then make sure that it is the cor­rect width and squarely aligned in the pul­ley grooves. If this is not cor­rectly aligned, the belt will be thrown off the pul­ley wheels.

Step 5 — Cor­rectly ten­sion new belt

Ten­sion the belt using a span­ner and a pry bar, and then check it with a ten­sion gauge.
Some vehicles have an auto­mat­ic spring ten­sion­ing sys­tem which saves you the time of adjust­ing the ten­sion manu­ally. Make sure you check the vehicle work­shop manu­al before com­men­cing the pro­ced­ure.

Step 6 — Start the engine

Start the engine, and observe the belt to make sure that it is prop­erly seated and oper­at­ing cor­rectly. Stop the engine again, and recheck the ten­sion.

Notes:

Com­mon causes or noise from the belt:

  1. Old belt
  2. Bear­ing in the pul­ley:
  3. Bad belt ten­sion­er: spray water, does it squel? Its prob­ably an old belt, or, the belt ten­sion­er spring is at its max­im­um
  4. Pul­ley mis­align­ment

Dia­gnose:

  1. Water bottle: spray it on the ribbed side. Does the squeak­ing stop?
    1. If it does, it prob­ably isn’t the bear­ing in a pul­ley
    2. If it doesn’t go away, its prob­ably a bad bear­ing in a pul­ley or belt ten­sion­er is bad or is a worn out belt.
  2. If the sound went away its either a:
    1. Bad belt
    2. Pul­ley mis­align­ment:
      1. Look at each pul­ley. Is the belt rid­ing straight?
      2. Watch the pul­ley: make sure the pul­ley is run­ning straight
        1. Altern­at­or, idler pul­ley, com­pressor pul­ley
  • The pul­ley is not com­pletely straight, so belt isn’t com­pletely straight.
    1. You can use a dif­fer­ent belt.
  1. What about a bad bear­ing in a pul­ley?
    1. Find the bad bear­ing: where is the noise?
      1. Then, grab pul­ley and shake it back and forth. It shouldn’t move.
      2. An altern­at­or pul­ley should not move at all. Idle pul­ley might move, that’s okay.

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