What Causes a Timing Belt to Fail?
There are many different types of failures that can and do occur. For the most part, timing belts fail when the owners fail to replace them according to the regular maintenance schedule. This may be at 75,000 miles or 100,000 miles. The timing belt change interval varies among manufacturers. If you have a larger engine such as a V6, it may not even have a timing belt but a timing chain that is designed to last as long as the engine. Nevertheless, considering the impact of synthetic lubricants reducing the internal wear of engines, the timing chain may fail before the engine is due for a rebuild.
The timing belt can be checked by removing the timing belt cover when you are having any type of service performed. If there are signs of fraying, dry-rot, or the teeth appear to be worn, you have to replace it immediately, no questions asked. Any type of abnormal wear is an emergency sign that your timing belt is about to fail. The belt can wear unevenly if the pulleys get bent. Other times, the belt will slip because the tensioner comes loose or the bearings of the tensioner begin to wear out. The tension of a timing belt is critical because the amount of play in it cannot be too tight or too lose.
How Complicated is a Timing Belt Replacement?
Replacing a timing belt is not something that should be performed by amateurs. If the timing is reset and it is even one tooth off, the entire engine can be destroyed instantly. Most vehicles require special tools to align the timing because it can be difficult to eye up markings. You should never take your vehicle to a shop that looks unprofessional and poorly organized when you need timing belt service.
Beyond the tricky alignments that are necessary to retime the basic timing of the pistons and valve train after belt removal, there is also the difficulty in removing it. Most vehicles require you to perform all of the following before you can take off the timing belt:
- Remove the starter
- Loosen engine mounts
- Remove the valve cover
- Remove the serpentine belt
- Remove the water pump pulley
- Remove the crankshaft pulley
- Remove the coolant expansion tank
- And much more …
Because many of the same parts have to be removed to replace the water pump, the water pump, thermostat, and gasket are usually replaced at the same time. A new timing belt kit may also include new rollers, a tensioner, and bolts to replace the original equipment.
Symptoms of a Failed Timing Belt
The only way that you will know that your timing belt has failed without a visual inspection is if you experience severe engine performance problems. If the belt has slipped even a half tooth, it will cause the vehicle to chug with no power even if you are pressing hard on the pedal. A compression test to see how well the engine pistons and valves are sealing is the only way to confirm that the basic timing is off. In most cases, however, the vehicle simply loses power all of a sudden and then won’t turn over to start if the timing belt does snap.
There are some vehicles that have what is called a non-interference engine. If you break a timing belt on one of these vehicles, you may have a second chance to install a belt and keep driving it as though no damage ever occurred. Yet, there have been reports of even so-called non-interference engines being damaged if the belt snaps at a high enough RPM speed. You may even be able to get away with minimal damage if the belt in an interference engine snaps at low speeds. However, the high speeds put the most stress on the belts, which makes it rare for a belt to snap at low RPMs.