Your engine's timing belt is the most important maintenance item in your car.
What Is A Timing Belt?
A timing belt is the ribbed belt that is placed in a specific configuration along one side of your engine to keep the crank and camshafts timed properly. Essentially, it keeps the top half of the engine (cylinder head, valves) in sync with the bottom half (crankcase, pistons).
Does My Car Have A Timing Belt?
If you have an older car from the 90s and below, odds are you have a timing belt. Some new car manufacturers, such as Audi, still use timing belts in their engine designs, but for longevity, many manufacturers have switched to metal timing chains that in theory last for the life of the engine. My advice would be to refer to your owner's manual and look up the maintenance schedule. If you don't have one, Google it. If you don't see a timing belt service listed, you have a timing chain.
You can also check here to see if your car is on the list of cars with timing belts.
When Should I Change My Timing Belt?
Manufacturers employ various schedules and measures for timing belt replacement, but the rule of thumb is 60,000 miles, or 5 years, whichever comes first.
Is My Engine Safe If My Timing Belt Snaps?
Well, that depends. There are two types of engine timing configurations: interference, and non-interference.
Here's What Happens When Your Timing Belt Snaps And How To Fix It
An interference type engine means that the valve's stroke and piston's stroke take up the same space in the cylinder, so the timing belt essentially keeps them from smashing into each other, since they do it at different times. If the timing belt snaps, they run into each other, causing bent valves (most common), cylinder head or camshaft damage, and possibly piston and cylinder wall damage. While it is possible that no damage could occur from a snapped belt on an interference engine, such a case is unlikely.
In a non-interference engine, the pistons and valves don't occupy the same space, so if the timing belt snaps, no valve or cylinder damage occurs. You just pop a new belt on, and the engine should theoretically drive normally.
You can find out if your engine is a non-interference or interference by referring to this list. If your engine isn't listed, Google it, as these lists aren't exhaustive.