Timing Belt Replacement
The engine in every car or truck has either a timing belt or chain connecting the crankshaft to the camshaft. This ensures the inlet and exhaust valves open and close at precisely the right moment: without it the engine won't run at all.
Timing chains are largely maintenance-free and will generally last the life of the engine. Unfortunately the same is not true for timing belts. These are made from fiber-reinforced rubber with teeth molded into the inner surface. The teeth engage with matching notches on the crank and camshaft pulleys, synchronizing the rotation of the two shafts.
With time and use the rubber ages and becomes less flexible. When this happens some of the teeth may be stripped off the belt, which will affect the timing of the valves. More commonly though, the belt will fail completely. If this happens the camshaft will stop turning and the valves will neither open nor close. However, the pistons will continue moving up and down in their cylinders. In some engines this results in the pistons hitting the valves. When this happens the valves will bend and the pistons may crack. The result is that the engine has to be torn down and completely rebuilt.
This disaster can be avoided if the timing belt is replaced periodically. Intervals vary depending on the design of the engine and the precise construction of the belt used, but for most vehicles the recommendation is somewhere 60,000 and 90,000 miles. (Check the handbook or call the dealer to get the actual figure for your car or truck.)
If you purchased your car new you’ll know when to get the belt changed, but if you buy used its not so clear-cut. Replacing a timing belt is an expensive job so some owners decide to sell rather than have the work done. For this reason, when you go to buy a used vehicle always ask if the belt has been changed. If you’re told it has, ask to see the invoice for the work or the service history. If there’s no evidence of the work being done, and the vehicle has done over 60,000 miles, it’s prudent to book it into the dealer for a belt replacement. The bill for this job, typically around $500, might sting but it’s a fraction of the cost of a new engine, so think of it as insurance.
Given the consequences of belt failure, you may wonder why car manufacturers don’t just fit timing chains. The official reason is noise: chains will inevitably slap and rattle, especially when cold, and buyers expect engines to be silent. The other reason is of course cost. Chain systems are more complicated and need lubrication, which adds yet more cost. As new car buyers are generally rather price-sensitive, the manufacturers prefer to make belt replacement part of the cost of ownership.
