GM Service Manual Online
For 1990-2009 cars only

Condition

Cause

Notice: Failure to follow the described timing belt inspection and maintenance may result in a broken timing belt and cause severe engine damage.

DEFINITION: The following describes conditions of the timing belt you may encounter during inspection and the possible causes.

Tooth is broken and/or tooth root is cracked

    • Camshaft jamming
    • Damaged camshaft/crankshaft oil seal and/or coolant leak
    • Old age
    • Tensioner not functioning properly

Back surface of the belt is cracked/worn/scratched/scored

    • Excessive cold starts
    • Tensioner jamming
    • Overheated engine
    • Interference with the belt cover

Side of belt surface is worn

    • Improper installation of the belt
    • Overload or misalignment of the cam drive components
    • Tensioner jamming
    • Heavy thrust loading against the idler guide flanges
    • Damaged idler guide

Teeth are worn

    • Poor belt cover sealing
    • Excessive belt tension
    • Tensioner jamming
    • Rough and/or scored cam sprockets

Clean break across fibers

    • Kinked belt before and/or during assembly
    • Foreign material under the belt

Oil/Coolant impregnated and/or swollen belt

    • Poor oil sealing
    • Coolant leak at pump
    • Poor belt cover seal