Poor alignment, improper tension, and worn sprockets will all result in increased timing belt fabric wear. After the fabric begins to wear, cracks will start to appear at the base of the teeth on the belt. Next, the tooth will separate from the belt. This is the most common type of belt failure.
The teeth have come off of this belt. Courtesy of Federal-Mogul Corporation.
To inspect the condition of a timing belt, twist it gently.
- Look for fraying, cracks at the base of the tooth, or loose fibers.
- Rotate the engine slowly by hand while checking it.
- Do not turn it more than 90°. The tensile cords in timing belts can be damaged.
- Wear on one side of a tooth indicates a misalignment problem.
- Check for oil leaks, which could damage the belt.
- Be sure that all of the small rubber gaskets that separate the parts of a multiple piece timing cover are reinstalled properly.