Timing Belt Cracking

When rubber timing belts operate at elevated temperatures (greater than 185°F) for prolonged periods of time, the timing belt material gradually hardens resulting in back cracking due to bending. These cracks typically remain parallel to the timing belt teeth and usually occur over land areas (in between timing belt teeth). This typically results in timing belts failure due to tooth shear, which often leads to tensile cord fracture.

Probable Cause:

• Sub-minimal timing belt pulley diameter

Corrective Action:

• Use correct timing belt pulley diameter

Probable Cause:

• Backside idler

Corrective Action:

• Change timing belt pulley material
• Increase diameter of backside idler

Probable Cause:

• Extreme low temperature at start-up

Corrective Action:

• Pre-heat drive environment

Probable Cause:

• Exposure to oil, solvents, harsh chemicals

Corrective Action:

• Eliminate or control condition
• Clean and protect drive

Probable Cause:

• Cocked bushing / timing belt pulley assembly

Corrective Action:

• Remount bushing and timing belt pulley