What is a timing chain or belt and where is it located?

The timing chain is the most important part of an automotive's engine timing system. Typically located on the front of the engine, the timing chain helps the crankshaft rotate in sync with the camshaft. While most older automobiles required one timing chain since they only had one camshaft inside the engine block, today’s more complex overhead cam motors can have as many as four cams and multiple chains.  

Much like the timing chain, timing belts connect the camshaft to the crankshaft. However, instead of being a metal link design, timing belts are made of reinforced rubber. In order to fit in tighter and more intricate engine designs, the timing belt system may incorporate the use of multiple hydraulic or mechanical timing belt tensioners, and belt tensioner or idler pulleys.

For an even more in-depth explanation of mechanical timing, belts, chains, how they each work, why they fail, maintenance and replacement tips and more, check out our timing belts Vs. timing chains guide.

How do I know the timing belt or chain needs to be replaced?

Since timing belts are rubber, they do require scheduled maintenance. The typical service life of an engine timing belt, at which point a replacement is required, is between 50,000 and 70,000 miles, but you should refer to manufacturer’s specifications for your specific application. A worn engine timing belt can break, causing a complete failure of the engine to operate. In vehicles equipped with Interference Engines, this could mean severe damage to the motor since the pistons and valves are only kept from colliding with each other by the timing belt’s movement. If the timing belt has been damaged prior to the recommended interval, a timing belt replacement must be obtained and installed immediately.

As for the timing chain, it's rare for them to break. They can often last as long as the engine itself, but this makes them prone to stretch out over time. To compensate, some automotives use timing chain tensioners to eliminate slack in the chain. But if the stretch is too far out of specification, or if the tensioner fails, the camshafts and crank will not be properly aligned with each other. As a result, the engine will lose power and typically trigger the “Check Engine” light on the dashboard. If there is something wrong with the timing chain and a replacement is required, this will need to be taken care of as soon as possible in order to get the car back on the road again.

Can I replace the timing belt or chain myself?

Timing belt and chain replacement can vary from vehicle to vehicle. It's important to seek out the proper information regarding your engine to see what tools you may need. These can range from a three-jaw gear puller to a harmonic balancer puller to a torque wrench. Some vehicles will require these types of tools in order to hold the camshafts and tensioner in place while the timing components are swapped out. We would recommend the advanced do-it-yourselfer who most likely has these tools readily available for this job, otherwise it's a good idea to leave it to the professionals to prevent any potential engine damage.

If you are tackling this job yourself, it's a good idea to have a service guide specific to your vehicle handy. The steps are not the same for every vehicle, but the process usually requires a disconnection of the negative battery cable, raising the vehicle on jack stands, draining the coolant, removing the air intake, disconnecting a few radiator and heater hoses, removing the radiator fan, loosening the serpentine belt, removing the water pump, removing the pulleys, removing the front timing cover, removing the harmonic balancer pulley, and, finally, pulling off the timing belt/chain. To prevent yourself from having to repeat much of the repair, we recommend replacing the water pump as well.