Advancements in rubber chemistry and improved engineering have resulted in a timing belt that is better and may last longer than a timing chain. That is, if the belt is installed and tensioned correctly. Timing belts are better. They are lighter, quieter and you don’t have to lube them. They can simplify many otherwise complex engine designs and they can drive multiple components. A regular inspection and scheduled replacement of the timing belt is a necessary maintenance procedure. The recommended replacement intervals may range from 36,000 – 100,000 miles, and they are documented in the owner’s manual and service manuals.
Some engines are classified as constant clearance or free-wheeling engines. Should a belt break or slip on the sprockets of one of these engines, no serious engine damage will result. Instead, just the inconvenience of a tow would be encountered. However, some engines are classified as interference engines and serious engine damage will occur with timing belt failure. When the belt breaks, the camshaft stops and the crankshaft doesn’t. This results in valves hitting pistons,bent metal and broken parts. Cylinder walls can be scored beyond repair and pistons can get holes punched through them. This can be prevented through regular inspections and replacement of the timing belt at the vehicle manufacturer’s recommended interval.
Proper belt tension is imperative for long belt life. Following a timing belt installation, some technicians set belt tension as if it were a V belt. The timing belt does not rely on friction to turn the sprockets; instead, the belt teeth carry the load. Belt tensioning procedures vary by engine design. Timing belts don’t stretch; instead, they wear and loosen from overtightening. Failure to follow the recommended installation and tensioning procedures can result in belt ratchet or slippage on the sprockets, thus costly engine damage.
The condition may occur immediately or in a few thousand miles. It may require a shock load to the belt such as an engine stall or an attempted push start (with manual transmission) to slip the belt on the sprockets. It gets difficult to explain why your belt failed in 10,000 miles and the original lasted 80,000 miles.