TIMING BELT - FAULT FINDING

 
TOOTH FACE WEAR  
 
FEATURES:    
Teeth FRONT FACES are worn with fibrous appearance. Teeth BACK FACES are maiden.
CAUSES:     
Extreme low tension.
GENERAL:  
Drive side of belt teeth are worn/undercut with fibrous white appearance. Back (non-drive) side of teeth are literally as new with no wear. Again a common failure due to extreme low tension. Belt rides out of pulley teeth and thus total belt load is concentrated on this reduced tooth contact. Compounded by the teeth outward movement wear is very visual and obvious.
ACTION:  
Tension as per OEM specification on a cold engine and repeat procedure during belt "settle-in" period.
   

 
LAND WEAR  
 
FEATURES:    
Polished or fibrous tooth roots/lands.
CAUSES:     
High tension.
GENERAL:  
Over-tensioning causes pulley teeth to bottom out and over-contact the tooth roots. Initially load polishing occurs which then develops to the elastic nylon fabric becoming frayed and fibrous in appearance. Belt will fail with possible other over-tension symptoms.
ACTION:  
Ensure tension is as per OEM specification on a cold engine and repeat procedure during belt "settle-in" period.