Instructions for changing a timing belt vary from vehicle to vehicle. Depending on the way your car's engine is set up, you may want to leave this tricky bit of maintenance to the pros.
Vehicle engines come in different sizes. The most common sizes are four cylinders, six cylinders and eight cylinders. Each engine also has a size in litres or cubic inches. Common 4-cylinder sizes are 2.2 litres, 2.3 litres and 2.4 litre. Some smaller engines are 1.6 litres and 1.8 litres. Common 6-cylinder engines are 3.0 litres and 3.8 litres. Engines with 8 cylinders commonly come in 4.8 litres, 5.2 litres and 5.7 litres.
Additionally, many of these engines have two or four cams. Even four-cylinder engines can have two cams. The vehicle sticker will generally tell you if the vehicle has a double-overhead cam or a single-overhead cam. If a vehicle has a double-overhead cam, it has two cams for each bank of cylinders.
An experienced mechanic should change the timing belt, as most vehicles have interference engines. This means that if the timing belt is not replaced correctly and the valves do not open at the right time and hit the pistons, your engine will suffer internal damage, which can cause thousands of dollars to repair.
Replacing the Timing Belt
The timing belt is located inside the timing belt cover on the front of the engine. Remove any accessories that prevent you from removing the timing belt. Remove the timing belt cover; if there is an upper and lower cover, remove both. Loosen the tensioner to remove the existing timing belt. There are different types of tensioners, and the timing-belt manual for your vehicle will explain how to work the type of tensioner in your vehicle.
Line the timing marks up on the cams and the crankshaft. Refer to a timing-belt manual to find the correct marks for your vehicle. Make sure the timing marks are still lined up. Starting at the crankshaft, wrap the new timing belt around the pulleys. Depending on the vehicle, you must leave slack on one side, usually the side away from the tensioner. Turn the engine over by hand. To do this, use a large ratchet to turn the crankshaft, turning the engine over two complete turns. The timing marks will line up again. If they do not, you must remove the timing belt and line up the timing marks before attempting to proceed.
Always turn the engine over by hand to make sure the timing marks are lined up. If you start the engine and the timing belt is not on in the proper position, you may bend a valve or put a hole in a piston. Once the marks line up properly, you can adjust the tensioner to the proper tension. Replace the timing belt cover, and the job is complete.