For 1990-2009 cars

Condition | Cause
--- | ---
DEFINITION: The following describes conditions of the timing belt you may encounter during inspection and the possible causes. Notice: Failure to follow the described timing belt inspection and maintenance may result in a broken timing belt and cause severe engine damage.
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