Problem – Diagnosis – Solution: Timing Belts

Keeping Things Running Smoothly

Timing belt checklist
Replacement interval  
Tension Tensioning system?
Damage to back of belt Idler pulleys?
Tension pulleys?
Foreign object?
Wear on tooth section Toothed pulleys?
Assemblies?
Pulley alignment?
Foreign object?
Incipient tears/chunking Toothed pulleys?
Assemblies?
Foreign object?
Pulley alignment?
Edge wear Pulley alignment?
Flanged pulley?
Contamination Leaks from engine system components?
Operating noise Tension?
Pulley alignment?
Assemblies?
Idler/tension pulleys?

 

Timing Belts
Problems and probable causes Solutions
Noise  
Excessive tension; belt whines, squeals Set correct tension
Insufficient tension: Belt knocks against cover Set correct tension
Edge wear  
Axes not parallel; belt runs against flanged pulley Check drive, align pulleys or replace them if necessary, replace belt
Sprockets with axial offset; timing belt cannot run in alignment Check drive, align pulleys or replace them if necessary, replace belt
Damaged flanged pulley Replace idler/tension pulley, replace belt
Bearing play on components Replace idler/tension pulley, replace belt
Wear on fabric at root of belt  
Excessive tension Replace belt, set correct tension
Excessive heat buildup in belt during operation Determine cause (e.g. check temperature stability), take corrective action, replace belt
Worn timing belt pulley Replace timing belt pulley, replace belt
Wear on tooth sidewalls/chipping at base and sheared-off teeth  
Excessive/insufficient tension Replace belt, set correct tension
Effect of foreign bodies Remove foreign object, make sure cover is fitted correctly, replace belt
Seized timing belt pulley or tension pulley Determine cause (e.g. defective bearing) and rectify problem, replace belt
Teeth and fabric break away from tooth base  
Leak from engine or in engine compartment (e.g. leaking oil, antifreeze, etc.) Repair leak, replace belt
Running marks on the toothed side  
Foreign body in the timing belt drive Remove foreign object, replace belt, make sure cover is fitted correctly
Flaws on timing belt pulley teeth due to foreign object or improper use of assembly tool Replace timing belt pulley, replace belt and install correctly
Timing belt damaged before / during installation Replace belt and install correctly
Cracking on back of belt  
Ambient temperature too high/low Determine cause (e.g. check temperature stability) and take corrective action, replace belt
Contamination by external media Replace belt, make sure cover is fitted correctly
Stiff backside idler Replace idler, replace belt
Aging Replace belt
Timing belt tears  
Foreign body in drive Remove foreign bodies/media, replace belt
Contamination by external media Replace belt, make sure cover is fitted correctly
Excessive belt pretension Replace belt, set correct tension
Kinking of belt before or during installation Replace belt and install correctly
Defective system components  
Bearing play Replace idler pulley, tension pulley and/or guide pulley
Damaged contact surface Replace idler pulley, tension pulley and/or guide pulley
Problem – Diagnosis – Solution: Timing Belts