WHAT IS A TIMING BELT, AND WHAT DOES IT DO?

Your timing belt or timing chain connects your crankshaft to your camshaft, or multiple camshafts, and conducts the intricate dance that plays out in your running engine, managing the input and output of air, fuel, and exhaust. A timing failure can catastrophically damage the engine, so read on to learn about how to maintain this important engine part.

WHAT IS THE PURPOSE OF A TIMING BELT?

Your timing belt coordinates the combustion cycle of the engine by connecting the crankshaft and the camshaft. The crankshaft rotates with the movement of the pistons and the camshaft controls the movement of the intake and exhaust valves.

Each cylinder has intake valves that open to allow air and fuel into the combustion chamber. Once the proper amount of air and fuel has entered the chamber, the camshaft closes the valves and the piston moves up in the cylinder, compressing the fuel/air mixture. The spark plug then ignites the mixture and it explodes, forcing the piston to move to back down the cylinder and rotating the crankshaft. At that point, the camshaft causes the exhaust valve to open, allowing the exhaust gases produced in the explosion to exit the cylinder, and the process starts over again.

All the valves and the piston need to move in a carefully coordinated dance for the process to work effectively, without blowing up the engine. The rotation of the crankshaft is transmitted through the timing belt to move the camshaft.

WHAT A TIMING BELT IS MADE OF

Modern timing belts are constructed of rubber, synthetic rubbers like neoprene, polyurethane, or highly saturated nitrile, with high-tensile strength reinforcing cords made of Kevlar, polyester, or fibreglass. The reinforcing cords will run the length of the belt, to reduce the tendency of the belt to stretch out over time. Timing belts have trapezoidal or curvilinear teeth cut into one of the sides and these teeth are specially shaped and sized to connect properly with the pulleys on the crankshaft and the camshaft.

Engines with timing chains will have oil flowing over the chain to lubricate and protect the parts. Oil can damage rubber, so engines with rubber timing belts will typically be constructed in a “dry” setup, where oil or coolant does not interact with the belt.

HOW LONG A TIMING BELT LASTS

Many experts will suggest that a timing belt should be replaced after 60,000 to 100,000 miles of driving, or seven to 10 years of service. The best bet for any vehicle owner, though, is to follow the recommendations of the manufacturer. Every vehicle manufacturer will lay out a service interval for the timing belt in the service manual of the vehicle, and it is essential to follow that interval to avoid a costly and inconvenient timing belt failure.