How to Know If a Timing Belt Is Bad

Many automobiles are equipped with timing belts that control the opening and closing of engine valves. Like most mechanical parts, timing belts will wear out over time and break, with costly consequences. Timing belts may fail without warning, but there are often signs beforehand.

Things You'll Need

• Owner's manual for your vehicle

Instructions

1. Be aware of changes in the performance of your vehicle's engine. An engine that frequently stalls or backfires, runs roughly with excessive vibration or produces noticeably less power may have a failing timing belt.

2. Note any squealing sounds or signs of smoke. These symptoms are telltale indications of a bad belt.

3. Have a mechanic visually inspect your vehicle's timing belt. Since timing belts are typically inaccessible and hard to see, this is a job for a professional. The belt should be replaced if there are cracks, fraying or other signs of damage.

4. Turn the key. If the engine cranks over unusually fast without starting, the timing belt is likely broken.

5. Remove the engine's distributor cap and see whether the rotor moves when the crankshaft is hand-turned. A lack of movement will confirm that the timing belt is bad.

Tips & Warnings

• Most automakers recommend changing timing belts every 60,000 to 105,000 miles. Check the owner's manual for your vehicle to find out when its timing belt should be replaced.

• A broken timing belt can cause major mechanical damage in vehicles with interference engines, making it key not to exceed the manufacturer's mileage limits for timing belts.

Resources

• Info on timing belts