Belt tension can be checked by pressing on the belt at the center point of its longest straight span. The belt should give approximately 1 / 4 - 1 / 2 in. (6-13mm). If the belt is loose it will slip, whereas if the belt is too tight it will damage the bearings in the driven unit.
For the purposes of V-belt tensioning, there are generally three types of mounting for the various components driven by the drive belt. The first method, referred to as pivoting type without adjuster, is designed so that the component is secured by at least 2 bolts. One of the bolts is a pivoting bolt and the other is the lockbolt. When both bolts are loosened so that the component may move, the component pivots on the pivoting bolt. The lockbolt passes through the component and a slotted bracket, so that when the lockbolt-s nut is tightened the component is held in that position. There are not automatic adjusting mechanisms used with this type of mounting.
The second method of component mounting, referred to as pivoting type with adjuster, is almost identical except for the addition of an adjuster of some sort. Usually the adjuster is composed of a bracket attached to the component and a threaded adjusting bolt. After loosening the pivoting and lockbolts, the adjusting bolt can be tightened or loosened to increase or decrease the drive belt-s tension. With this type of mounting, you do not have to hold the component in a tensioned position and tighten the pivoting and lockbolts; the adjusting bolt does the job for you.
Some versions of this method of mounting use an adjuster which is built into one of the components mounting braces. The brace attaches the component to the engine and incorporates a threaded adjuster in its mid-span, so that when the threaded adjuster is turned the brace shortens or lengthens. This in turn increases or decreases the amount of tension on the component.
The third type of mounting, referred to as stationary type, is designed so that the component is mounted on its brackets. There are no pivots or lockbolts, and the component is not designed to be moved. Rather, this type of mounting uses an extra tensioner idler pulley assembly. The drive belt is tensioned by adjusting the position of the idler pulley, usually accomplished by turning the adjuster bolt on the idler mechanism.
Periodic drive belt tensioning is not necessary, because an automatic spring-loaded tensioner is used with these belts to maintain proper adjustment at all times. The tensioner is also useful as a wear indicator. When the belt is properly installed, the arrow on the tensioner housing must point within the acceptable range lines on the tensioner's face. If the arrow falls outside the range, either an improper belt has been installed or the belt is worn beyond its useful life span. In either case, a new belt must be installed immediately to assure proper engine operation and to prevent possible accessory damage.
These engines, with the exception of the 1MZ-FE and 3MZ-FE engines, are equipped with automatic belt tensioners. Adjusting the belt tension is not possible or necessary.3.0L (1mz-FE) And 3.3L (3mz-FE) Engines
- Measure the belt deflection by applying 22 lbs. (98 N) of pressing force to the mid-point on each drive belt between the crankshaft pulley and the alternator (generator), or vane pump pulley.
- When checking a belt used for over 5 minutes, confirm the deflection value is within the specified one.
When reinstalling a belt used for over 5 minutes, perform the check based on the used deflection value.
- Refer to the chart with belt deflection values as shown.
- Measure the drive belt tension and refer to the chart for the correct tension values as shown.
- When using a belt tension gauge, confirm the accuracy first by using a master gauge.
- Check the drive belt tension and deflection value after 2 revolutions of engine cranking.
- Disconnect the negative battery cable.
- Loosen the component-s lockbolt and pivoting bolt only enough for the component to move.
Using a strong wooden, plastic or metal pry tool, move the component either closer to, or farther away from, the engine to provide the correct tension on the belt.
WARNINGIf using a metal pry tool, always wrap the end with a rag or towel to prevent accidentally damaging the component from undue stress.
- Once the proper amount of tension is applied to the drive belt, hold the pry tool with one hand while tightening the lockbolt securely with the other hand.
- Release the pressure from the pry tool and tighten the pivoting bolt securely.
- Double check the drive belt-s tension, in case the component moved slightly while tightening the bolts.
- Connect the negative battery cable.
Idler Pulley With Adjusting Bolt
- Loosen the idler bracket pivot bolt and locking bolts.
- Adjust the belt tension by inserting the proper size ratchet in the square slot of the idler bracket and rotating the bracket until tension is applied.
- While holding the tension on the belt with the ratchet, tighten the locking bolts, then the pivot bolt.
- Loosen the mounting/pivot bolt behind the idler pulley.
- Swivel the idler pulley with a pair of pliers or a wrench on the bearing mounting until the proper tension is achieved.
- While holding the idler pulley, at the proper tension, tighten the mounting/pivot bolt.