Accessory Drive Belts 1
Drive Belt Routings
Inspection
As drive belts wear, they tend to stretch, or lengthen. As a belt stretches over time, the tension decreases, which causes the belt to slip on the pulleys. This slippage not only causes operating problems (erratic steering, high engine temperatures, and charging system problems), but also can greatly accelerate wear and damage to the belts themselves. Excessive slippage can cause a drive belt to glaze, overheat, and eventually break. Regular inspection and adjustment of the accessory drive belts will prolong their life, and ensure proper operation of belt-driven components.
To thoroughly inspect accessory drive belts, it's advisable to remove the lower engine cover, and view the condition of the belts through the right front wheel housing. If necessary, raise and safely support the vehicle to allow access. Viewing the belts from the engine compartment is sometimes possible, but belt-driven components such as the power steering pump and air conditioner compressor are often out of view from the engine compartment.
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 always best to replace all drive belts at one time, as a preventive maintenance measure, during this service operation.
Inspect the drive belt 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.
Tension MeasurementTo check belt tension on V-belts, push in on the drive belt about midway between the crankshaft pulley and the driven component. If the belt is less than 39.4 in. (1m) long, it should deflect between 1 / 16 - 1 / 8 inch (2-5mm). For longer belts, it should deflect between 3 / 8 0.40- 5 / 8 inch (10-15mm). Belt size is usually printed on the back side of the belt. If it can't be read, it's probably time to replace it.
To compensate for the stretching of the accessory drive belts, a means of adjustment is necessary. This can be accomplished by changing the distance between the crankshaft pulley and the driven component, or by means of a tensioning device using an idler roller.
The current trend for most manufacturers is the use of a serpentine type drive belt that is kept in adjustment using an automatic belt tensioner. These automatic tensioners can be either a pivoting arm-type or an eccentric type.
The rotary method (most common with V-belts) involves the driven component being rotated on a pivot. A slotted bracket and or arm(s) is/are used to hold the component in place once the belt tension is set. Within this method, there are four variations. The most basic variation is a simple slotted bracket with a bolt. This requires pulling or pushing on the driven component to achieve the desired belt tension. Some early models use a spring-loaded alternator bracket that sets the belt tension after the slotted bolt is loosened.
Other models use a rack and pinion design on the slotted adjustment bracket. This allows for effortless belt adjustment, since the pinion gear has a hex head and can be turned with a wrench to make adjustments. The final variation of the slotted style adjustment design uses a long adjuster bolt that pushes or pulls the driven component once the slotted bolt is loosened.
Poly-Ribbed BeltsThe engines equipped with poly-ribbed belts are equipped with automatic adjusters, and Do NOT require adjustment. The spring action of the tensioner compensates for the stretching of the belt. The belts should be checked for belt stretch, wear or fluid damage and replaced if necessary. Check the maintenance recommendation chart for recommended routine replacement intervals.
V-BeltsPlain Slotted Brackets
- As a safety precaution, disconnect the negative battery cable.
- Loosen the adjustment nut/bolt in the slotted bracket. Slightly loosen the pivot bolt.
- Pull (don't pry) the component outward to increase tension. Push inward to reduce tension. Tighten the adjusting nut/bolt and the pivot bolt.
- Recheck the drive belt tension, readjust if necessary.
- Reconnect the negative battery cable.
- As a safety precaution, disconnect the negative battery cable.
- Loosen the alternator pivot bolt, and the slotted bracket bolt, and the bracket mounting bolt.
- Adjust the V-belt by turning the large nut (the pinion) nut while checking the belt deflection.
- While holding the pinion nut steady, tighten the slotted bracket bolt to hold the adjustment setting.
- Tighten the alternator pivot bolt, and the slotted bracket mounting bolt.
- Recheck the drive belt tension and readjust if necessary.
- Reconnect the negative battery cable.
- As a safety precaution, disconnect the negative battery cable.
- Loosen the slotted bracket bolt(s), and slightly loosen the pivot bolt(s).
- If equipped, loosen the locknut(s) on the adjustment bolt(s).
- Turn the threaded adjustment bolt(s) as necessary to achieve the correct tension.
- Tighten the pivot bolt(s) and the slotted bracket bolt(s) securely.
- While holding adjustment bolt(s) in position, tighten the lock nut(s) if equipped.
- Recheck the drive belt tension and readjust if necessary.
- Reconnect the negative battery cable.
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