SKF Timing Belt Kits - SKF.com

Troubleshooting and failure analysis
86
For all other components
Symptom/Appearance Probable cause Corrective action
The plastic idler pulley appears • Extreme environmental wear Replace
to be worn on belt tracking area (i.e., heat, water, stones)
On plastic idlers, pulley has a chip in it • Stone damage Replace
• Faulty installation practices
Tensioner bearing has been • Stone damage Replace
marred in belt tracking area • Faulty installation practices
Tensioner bearing shows signs • Coating on pulley has worn off Replace
of corrosion Note: it is normal for coating
to wear off belt tracking area
Bearing has excessive wobble (free rock) • Bearing failure Replace
• Excessive load on pulley
• Belt is not tracking properly over pulley
Bearing Appearance Probable cause Corrective action
Grease appears to be • Seal degradation. Replace
leaking out of the bearing • Excessive radial internal clearance in brg.
Bearing seal is missing or damaged • Worn pulley Replace
• Environmental damage
(i.e., heat, water, stones)
Bearing seal looks damaged. • Faulty installation practices Replace
• Environmental damage
(i.e., heat, water, stones)
Loose, sticking or seized pulley Probable cause Corrective action
Tensioner bearing is seized and will not • Bearing is damaged Replace
rotate freely
Tensioner bearing does not rotate smoothly • Radial internal clearance in brg. is too low Replace
or has a sticky feel to it when spun • Bearing fit in pulley is tight
Pulley and bearing have relative motion • This signifies the bearing is Replace
not being constrained
Noise Probable cause Corrective action
Bearing makes a high pitched whine or • Worn bearing Replace
hooting noise after the engine is started • Bearing fit is incorrect
Noise lasts up to three minutes
Bearing makes a high pitched whine • Bearing is not functioning properly Replace (During normal operation,
in operation bearing is very quiet)
Bearing assembly rattles when shaken • Bearing cage is broken Replace
• Balls in bearing are loose
• Bearing is void of lubricant
Tracking Probable cause Corrective action
Belt does not track properly • Bearing is not fixed to the correct Replace
on idler belt tracking surface depth in pulley
• Belt tracking surface is not square
to bearing mounting surface
• Pulley tracking surface is tapered
(Crowning or bowing of belt tracking
surface is sometimes intentional)