When to Replace a Timing Belt
When to Replace your Timing Belt
What is a timing belt? Is it a belt with a timer that goes off reminding you its time to put on your pants? Thankfully, no. It is a toothed belt made of rubber and fiber used in some engines to match the timing of the valves to the motion of the pistons. Let's explain further.
A typical engine has one crankshaft. This shaft is connected to the pistons and converts their reciprocating motion into rotational force and transmits that force to whatever device the engine is powering.
Most automotive engines also contain at least one camshaft. Some have up to four. The camshaft rotates at exactly one-half the speed of the crankshaft and is responsible for opening and closing the intake and exhaust valves at the proper time to allow the fuel/air mixture and exhaust gases to pass through the engine.
Because these shafts must be precisely rotated in relation to each other, they are connected together by a timing chain or timing belt. You can determine which one your engine contains by consulting a mechanic, the dealership, or your owners manual. If your engine has a timing chain, it typically will not need changing unless you are completing a major overhaul. If, however, your engine has a timing belt, it must be replaced at certain intervals.
The safest way to determine when to change your timing belt is by consulting the maintenance schedule published by the car's manufacturer. This is typically anywhere between thirty thousand to one hundred thousand miles. (Example: You bought a new car and the car maker recommends sixty thousand mile intervals. You should change the timing belt when the odometer reads sixty thousand, again when it reaches one hundred twenty thousand, and so on for the life of the car.)
How important is changing the timing belt? As with any automotive belt, we all know they do not last forever. A timing belt will fail one of two ways. The teeth will wear to the point where they strip off the belt and can no longer keep the shafts timed. Or, the belt will simply become weak enough to break. Either way, your car just turned from a means of transportation into a multi-ton paper weight. You will not be able to drive any further. It will have to be towed somewhere to be repaired.
Things may get worse. There are two types of engines. Non-interference and interference. (Again, you can determine which one you have by consulting a mechanic or the dealership.) In a non-interference engine, the valves and the pistons never occupy the same space. In an interference engine, the valves and pistons do occupy the same space, but at different times. If your engine is non-interference, you can have the timing belt replaced and be back on the road.
If, however, your engine is interference, you will have much bigger problems when the timing belt fails. Because the valves occupy the same space as the pistons and there is no longer a timing belt to make sure this occurs at different times, the pistons and valves will attempt to occupy the same space at the same time. If this sounds bad to you, you are correct. Valves will bend, pistons may break, the engine will have to be torn down, inspected, and rebuilt as necessary (read this as, "Your wallet will become much thinner."). Why do they make interference engines? It allows for higher compression ratios and farther opening valves. This makes the engine more powerful and efficient for its size.
To sum up, change your timing belt at the intervals suggested by your car's manufacturer. Change it immediately if it gets contaminated with chemicals such as coolant or oil. Change it immediately if you are doing other maintenance and notice it is damaged. And unless it has just been replaced, change it if you must remove it to complete other maintenance.
Follow these guidelines and you should save yourself an unexpected roadside breakdown and towing fee, not to mention an expensive repair bill.
