Richard, please exercise caution when working on belts on your engine. If you haven't already I would suggest disconnecting the negative battery terminal to ensure nothing will move when your hands are in the belt area. Your question did not indicate what type of Toyota or year it is. I have a two type of belt answer: On my 87 Toyota truck, the "V" belt idler for my AC pump was adjusted by loosening the nut in the center of the pulley wheel, then adjusting a bolt behind the idle pulley in or out as needed. Turing the bolt moves the pulley in or out depending on what way you turn it. When the belt is tight, you then lock the pulley in place by tightening the bolt in the center of the pulley. My alternator was the belt tensioner for the second belt. The top nut would allow the alternator to move, but you also had to loosen the lower bolt and nut under the alternator to allow it to pivot on that bolt. The top nut was tightened when the desire belt tension was achieved. The lower bolt is tightened back as well. Over tightening the belt can put extra wear on the alternator and water pump bearings, so use caution. If your vehicle is newer, the belt might be flat or a serpentine belt type. These types of belts are kept tight by a spring load from the idler pulley. The spring is inside the round housing part of the idler arm. That end is usually attached to the engine. The pulley is on the swing part of the arm and is used to apply tension to the belt to keep in on all the other pulleys. In the casting, you will see a square hole for your 3/8" socket wrench to fit into. This allows you use your wrench to release the tension from the belt. The spring and movement of the arm applies the required tension to the belt and does not need to be adjusted, but just inspected every so often to make sure they still move. In your vehicle engine area, you might have a small diagram showing the route the belt takes through your accessories on the engine. When the pulley arms get old, they can stick and not apply the proper tension to the belt. The belt does stretch when it first is used and when it gets older. Your new belt circumference might also be too big now and the pulley arm might be at its limit of travel. I would suggest taking it back to who did the work to have them correct this. You can check the tension by pressing down on the belt between two pulleys and note the movement of the idler pulley arm. The pulley arm should move back when your release hand pressure to the belt. I hope this helps. Please leave feed back if this was useful to you. Thank you.
your advice was extremely helpful and I apologise for not giving the model and year. The vehicle is a 1997 Toyota Landcruiser Prado, with 3 micro V belts and an idler pulley. All three belts seem to tighten from the alternator by loosening the top bolt and turning a bolt located under the alternator. My problem is that nothing is moving when I turn this adjusting bolt.
Hi Richard. If you have three separate belts, I would think you would have more than one location to adjust these individually. I never have worked on a Land cruiser so I could be wrong.
Looking at the alternator, does it appear to pivot on one bolt and on the other mounting bolt run through a slotted or elongated hole in the other mount?? Or does it appear to be basic mounting holes to just attach the alternator and hold into one position. If both appear to be just the same size as the bolt, the alternator might not be the unit to pivot to adjust the belts. Also, if more than one belt runs through the alternator pulley at different angles or directions, it would make it difficult for the alternator to tighten both or all three belts at the same time. The alternator might adjust for one, but he others might use something else to tighten them. I would suggest looking at any idler pulleys and other devices on each of the belts separately to see if they can be moved. Please examine the other idle pulleys and accessories and let me know what you find. A picture of the belt diagram in your vehicle engine area would be helpful to me if you can send that.
Thanks
Todd
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INSPECTION
See Figures 1, 2, 3, 4 and 5
Check the condition and tension of all drive belts every 12,000 miles, or at least once a year. Loose drive belts can lead to poor engine cooling and diminished alternator, power steering pump, air conditioning compressor, or emission air pump output. A belt that is too tight places a strain on the bearings in the driven component.
Fig. Fig. 1: There are typically 3 types of accessory drive belts found on vehicles today
Fig. Fig. 2: An example of a healthy drive belt
Fig. Fig. 3: Deep cracks in this belt will cause flex, building up heat that will eventually lead to belt failure
Fig. Fig. 4: The cover of this belt is worn, exposing the critical reinforcing cords to excessive wear
Fig. Fig. 5: Installing too wide a belt can result in serious belt wear and/or breakage
Replace any drive belt that is glazed, worn, cracked, or stretched to the point where correct adjustment tension is impossible. If two belts are used to drive a component, always replace both belts when replacement is necessary. After installing a new belt, run the engine for ten minutes, shut OFF the engine and recheck the belt tension. Readjust if necessary.
ADJUSTMENT
See Figures 6, 7, 8, 9 and 10
Fig. Fig. 6: Engine belt tension chart-2.2L engines
Fig. Fig. 7: Engine belt tension chart-1987-89 2.5L engines
Fig. Fig. 8: Engine belt tension chart-2.6L engines
Fig. Fig. 9: Engine belt tension chart-1990-93 models
Fig. Fig. 10: Engine belt tension chart-1994-95 models
Two popular methods of checking drive belt adjustment are; the Belt Tension Gauge Method and the Belt Deflection Method. The former requires a special gauge and the latter requires a straight edge and scale or just a good eye for measurement. The deflection method will be used in the following belt replacement instructions. A rule of thumb for checking belt tension by the deflection method is to determine the midpoint between two pulleys of the drive belt and press down at that point with moderate thumb pressure. The belt should deflect to the measurement indicated in the following installation procedures. Adjustment is necessary if the belt is either too loose or too tight.
WARNING
A belt adjustment which is either too loose or too tight will eventually damage the accessory that belt is driving. A too loose adjustment allows free-play in the belt which could transfer a whipping motion or shock to the accessory drive pulley. Similarly, a belt which is too tight will preload the accessory bearings, leading to early failure.
REMOVAL & INSTALLATION
See Figure 11
Raise the front of the vehicle, support on jackstands and remove the lower splash shield if access is hampered due to space limitations when changing drive belts.
Fig. Fig. 11: Support the vehicle, then remove the lower right side splash shield for access to the drive belts
2.2L Engines
A/C COMPRESSOR DRIVE BELT
See Figures 12, 13 and 14
Fig. Fig. 12: A/C compressor drive belt adjusting points-2.2L engines
Fig. Fig. 13: Loosening the locking screws for A/C compressor drive belt removal
Fig. Fig. 14: Removing the A/C compressor drive belt from under the vehicle
Fig. Fig. 15: Alternator belt adjustment-2.2L engine
Fig. Fig. 16: Loosening the locking screw for alternator drive belt removal
If removal of the alternator belt is required, the A/C belt must first be removed.
Fig. Fig. 17: Air pump belt adjustment-2.2L engines
When servicing the air pump, use the square holes provided in the pulley to prevent camshaft rotation.
Fig. Fig. 18: Drive belt adjustment points-2.5L engines
Fig. Fig. 19: Drive belt adjustment points-2.6L engines
Fig. Fig. 5: 3.8L belt schematic-1993 shown
To install:
After adjustment is satisfactory, tighten the idler pulley bolt, and then tighten the adjustment bolt.
Reconnect the negative battery cable.
When replacing more than 1 belt, it is a good idea to make note or mark what belt goes around what pulley; this will make installation easier if you mix up the belts.
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have you tried just changing the belt ?
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