Inspection of the Belt and Pulley

sd mm 01.01.002
  1. Check the belt contact surfaces for damage. See Fig..

    1. Abrasion

    2. Chunk-out

    3. Improper Install

    4. Cracking

    5. Pilling

    6. Uneven Rib Wear

    7. Misalignment

    8. Gravel Penetration

    Fig. 1, Damaged Belts

  2. Inspect the belt for glazing. Glazing is represented by shiny sidewalls, and is caused by friction created when a loose belt slips in the pulleys. It can also be caused by oil or grease on the pulleys.
  3. Check the belt for ply separation. Oil, grease, or belt dressing can cause the belt to fall apart in layers. Repair any oil or coolant leaks that are affecting the belts before replacing the drive belts. Do not use belt dressing on any belt.
  4. Check the belt for a jagged or streaked sidewall. Jagged or streaked sidewalls are the result of foreign objects, such as sand or gravel in the pulley, or a rough pulley surface.
  5. Check for tensile breaks (breaks in the cord body). Cuts in a belt are usually caused by foreign objects in the pulley, or by prying or forcing the belt during removal or installation.
  6. Check for uneven ribs on serpentine belts. Foreign objects in the pulley will erode the undercord ribs, causing the belt to lose its gripping power.
  7. For EPDM belts, check the belt for material loss, which causes the belt to seat further down in the pulley and to ride directly on the pulley tips. See Fig..

    1. New Belt

    2. Worn Belt

    3. Material loss results in belt riding directly on pulley tips.

    Fig. 2, Six-Rib Serpentine Belt (cross section view)

  8. For Neoprene belts, check the drive belts for cracks. Small irregular cracks are usually signs of an old belt.
  9. Inspect the pulleys for excessive play or wobble. Excessive play or wobble indicates a failure of the pulley bearing. Check for belt squealing or squeaking. Replace the bearings as necessary.

    10. Note: If it is difficult to distinguish the location of a supposed bearing noise, place a stethoscope on the component being checked, not the pulley, to isolate the area from outside interference.

  10. Inspect all pulleys for foreign objects, oil, or grease in the grooves.
Note:
Parent topic: Engine Drive Belt Inspection
Document Number: 0000119593
Manual Publication Date: 2024-05-23
Topic Publication Date: 2024-10-31