Diagnostic Aids
Pulley misalignment can cause the drive belt to fall off the drive belt pulleys.
An extra load that is quickly applied and released by an accessory drive component may cause the drive belt to fall off the pulleys. Verify that the accessory drive components operate properly.
If the drive belt is the incorrect length, the drive belt tensioner may not keep the proper tension on the drive belt.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This inspection is to verify the condition of the drive belt. Damage may have occurred to the drive belt when the drive belt fell off. A damaged drive belt may cause the drive belt to fall off. Inspect the belt for cuts, tears, sections of ribs missing, or damaged belt plys.
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Misalignment of the pulleys may be caused from improper mounting of the accessory drive component, incorrect installation of a pulley, a bent pulley or pulley shaft. Test for a misaligned pulley using a straight edge in the pulley grooves across two or three pulleys. If a misaligned pulley is found refer to that accessory drive component for the proper repair procedure.
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The inspection of the pulleys should include inspecting for any damage to the pulleys that would prevent the drive belt from not seating properly in all of the pulley grooves or on the smooth surface of a pulley.
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Accessory drive component brackets that are bent or cracked could cause the drive belt to fall off.
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Inspecting the fasteners can determine if a wrong bolt, nut , spacer, or washer was installed. Missing, loose, or wrong fasteners may cause pulley misalignment . Improper tightening of the fasteners may cause misalignment of the accessory component bracket.
Step | Action | Yes | No |
|---|---|---|---|
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Notice: Do not use belt dressing on the drive belt. Belt dressing causes the breakdown of the composition of the drive belt. Failure to follow this recommendation will damage the drive belt. DEFINITION: The drive belt falls off the pulleys or may not ride correctly on the pulleys. | |||
1 | Did you review the Drive Belt Symptom operation and perform the necessary inspections? | Go to Step 2 | |
Inspect for a damaged drive belt. Did you find the condition? | Go to Step 3 | Go to Step 4 | |
3 | Install a new drive belt. Refer to Fan Belt Replacement and Generator and Air Conditioning Compressor and Power Steering Pump Belt Replacement . Does the drive belt continue to fall off? | Go to Step 4 | System OK |
Inspect for misalignment of the pulleys. Did you find and repair the condition? | Go to Step 12 | Go to Step 5 | |
Inspect for a bent or dented pulley. Did you find and repair the condition? | Go to Step 12 | Go to Step 6 | |
Inspect for a bent or a cracked bracket. Did you find and repair the condition? | Go to Step 12 | Go to Step 7 | |
Inspect for improper, loose or missing fasteners. Did you find loose or missing fasteners? | Go to Step 8 | Go to Step 9 | |
8 | Tighten any loose fasteners. Replace improper or missing fasteners. Refer to Fastener Tightening Specifications . Does the drive belt continue to fall off? | Go to Step 9 | System OK |
9 | Test the drive belt tensioner for proper operation. Refer to Drive Belt Tensioner Replacement - Cooling Fan and Drive Belt Tensioner Replacement - Generator, Air Conditioning, and Power Steering . Does the drive belt tensioner operate correctly? | Go to Step 11 | Go to Step 10 |
10 | Replace the drive belt tensioner. Refer to Drive Belt Tensioner Replacement - Cooling Fan and Drive Belt Tensioner Replacement - Generator, Air Conditioning, and Power Steering . Does the drive belt continue to fall off? | Go to Step 11 | System OK |
11 | Inspect for failed drive belt idler and drive belt tensioner pulley bearings. Did you find and repair the condition? | Go to Step 12 | Go to Diagnostic Aids |
12 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 |
