How Does the Timing Belt Work?by Derek Odom
The timing belt is located at the front of most engines, which may not necessarily mean the front of the vehicle. On older, rear-wheel-drive vehicles and newer trucks and luxury cars, the timing belt can usually be found just behind the radiator fan that is toward the front of the vehicle. However, on newer, front-wheel-drive models, the engine sits sideways in the engine compartment, so the timing belt will be located on the side. On older vehicles and newer V8 models, the timing belt is actually a chain, and on smaller vehicles it is a rubber belt, much like the V-belts that you find on alternators or power steering components.
The purpose of the timing belt is to keep the engine's crank and camshaft turning at the same rate. In this manner, the exhaust and intake valves will open and close at the proper times, keeping the internal combustion part of the engine operating smoothly. On older vehicles, this process can be fine-tuned by twisting the distributor slightly to the left or right, which will provide maximum precision of the process. Newer models are mostly computer controlled, and adjusting the timing is an automatic process that takes place depending on what the computer reads about the engine processes happening. Older vehicles have a vacuum line going to the distributor, which will slightly advance or retard the timing as necessary, such as for fast takeoffs or passing, reducing the risk of pre-detonation, which means the explosion of fuel happens when the piston is not at the top of its stroke. This causes major heat and a noticeable loss of power.
Although the replacement of broken timing belts or chains is best left to a mechanic, those who are so inclined can change them without employing a shop, but it is an extensive process. The crank and cam pulleys must be removed, as well as the timing cover. Usually, the radiator fan (if present) and the radiator is best removed as well. There are dots painted on both the cam and crankshaft gears, which should be aligned before placing the new belt or chain on the vehicle. This gives a good base point for the timing, and fine-tuning adjustments can be done with the motor running. Inspect both the gears to make sure nothing broke when the timing belt let loose, as well. An engine with no timing belt will not run, so it is necessary to replace a broken one before driving the vehicle.