Timing belts are one of the most crucial parts of your vehicle's overall maintenance regimen. The timing belt transfers energy from the central camshaft to the upper cams. This transfer facilitates the timing between when the combustion chambers in the engine block and the fuel and air injection in the upper block (heads) happens.
In addition, most timing belts also operate the water pump to move coolant around the engine and often the oil pump which moves oil (lubricant) around the engine.
Timing belt failure always means the engine stops running. It can sometimes mean serious engine damage as well. So paying attention to the timing belt replacement intervals given by the engine's manufacturer are important.
In most vehicles, the timing belt replacement interval is between 50,000 and 70,000 miles with some going as long as 100,000 miles between changes. So this critical piece of your vehicle's infrastructure is not something that requires replacement often.
A qualified mechanic will usually charge between $300 and $800 for a timing belt change, depending on the make and model of the vehicle. Some cars will have a higher cost due to the difficulty of getting to all of the components that require removal in order to get to the timing belt itself. This is especially true of front wheel drive compact cars.
If you aren't sure of the interval for your timing belt replacement, count on it being around 60,000 miles.
Belts vs. Chains
Many vehicles, especially those made before the 1990s, have chains rather than belts. The good news for those vehicles is that those chains rarely need replacing. The bad news is that when they do, it's often the death knell for the engine behind the chain because the timing has likely been off for some time and has lead to other serious engine troubles.
Chains were replaced by belts because belts are simpler, cheaper, lighter weight, and often provide better performance value for smaller engines. The bad news is that they require regular replacement - and that is a costly procedure.
Interference vs. Non-interference
Two types of engines mean two types of timing belt options. Most people know that if the timing belt goes, their engine stops working. In interference engines, however, if the timing is off, the valves and pistons can collide, causing catastrophic failure and ending in the engine being scrapped or requiring a full overhaul.