The timing belt or chain is one of the most important maintenance items on an automotive engine, yet it is frequently the most neglected. Failure to follow the required maintenance schedule for the timing belt or chain can lead to very expensive repairs to other engine components.
One reason so many drivers neglect timing belts is the long service intervals. Unlike oil changes that typically occur several times per year, timing belts typically last at least 50,000 to 60,000 miles, and timing chains can go 100,000 miles or more before needing replacement.
Why is the timing belt or chain so important? Like a runner, an engine needs to breathe in order to produce power. Athletes alternately inhale air and exhale carbon dioxide. Engines also draw in air and then exhale exhaust gases. Every cylinder in an engine has from two to four valves, half of which allow air and fuel in and the other half providing a path to let exhaust out.
Each valve has a spring attached to it, keeping it tightly closed. The valves are opened by a rotating camshaft with lobes that push down on the top of each of the valve stems in turn. As the lobe passes, the spring pushes the valve back up.
For an engine to work, the opening of these valves must be carefully synchronized with the rise and fall of the pistons. If the valves open too early or too late, the engine can run poorly or not at all. Worst of all, because the valves must open as the piston falls, if the valve timing is too far off, the pistons and valves can collide, causing severe damage inside the engine.
In order to keep everything in sync, the camshafts are driven by the crankshaft.
With just a few notable exceptions, the camshafts on virtually all modern engines are mounted on top of the cylinder heads at the opposite end from the crankshaft, an arrangement referred to as “overhead cam.” The result is a fairly long drive mechanism that is typically either a toothed belt or a chain drive.
Chains have a durability advantage over belt drives, but they are noisier than belt drives. A toothed rubber belt can stretch as it ages; this can leave the camshaft out of sync with the crankshaft. Chains can also stretch or break, but they generally last about twice as long as belts.
Whether an engine has a belt or chain drive, the service interval will be listed in the owner’s manual and manufacturers strongly advise that drivers follow the recommendations. Unlike changing oil or an air filter, replacing a timing belt or chain is generally not the type of service most people can handle at home. It typically requires removing most of the parts at the front end of the engine such as the alternator, power steering pump and air conditioning compressor. In a front-wheel drive vehicle with the engine mounted left to right, this area can be very tight and difficult to work in.
When the time comes to replace the timing belt or chain, it’s best to bring the car to a qualified service facility such as the dealer that sold the car. The technicians there will have special training on how to do this operation and all of the specialized tools that may be needed. They will also know how to make sure that the crankshaft and camshafts are all correctly aligned so the engine runs properly.
Modern engines can run for many miles and years with the original timing belt or chain. When it is time to replace it, however, it’s best to get the job done promptly and properly by a professional who offers a warranty on the work. Whatever option you choose, delay can be costly.
Contact us today and we’ll help steer you in the right direction.