What is a timing chain, and is it the same thing as a timing belt? The simple answer is that one is a chain and one is a belt. It’s important to first understand the basics of mechanical engine timing to know why exactly your Chevrolet Cobalt needs a chain or a belt. Most cars have four-stroke gas engines since the combustion process has an exhaust stroke, a power stroke, a compression stroke and an intake stroke. Throughout the process, the camshaft rotates one time, and the crankshaft rotates two times. This relationship between the spinning of the crankshaft and camshaft is known as “mechanical timing.” In other words, this is what controls the movement of the valves and pistons inside your engine’s cylinders. The valves must open at a specific time that coincides with the pistons. If they don’t, the engine won’t work right, if it works at all.
Timing Chain vs. Timing BeltThe first American-built car equipped with a rubber timing belt emerged in the mid-1960s. Before that, every four-stroke engine was equipped with a timing chain. Compared to a chain, a timing belt is very quiet. Although belts are strong, they are prone to wear-and-tear. Most manufacturers recommend that you replace your timing belt every 60,000 to 100,000 miles. The timing belt runs through pulleys equipped with belt tensioners. As the name implies, the belt tensioner ensures that the belt has proper tension at all times. Typically, belt tensioners wear out around the same time as the belt, and most people replace the two together. Timing chains act in the same way, but they tend to last longer. Although some car manufacturers suggest replacing the timing chain at specific intervals, other car makers suggest that a single timing chain will last throughout the life of the car. Timing chains resemble bicycle chains, and they’re noisier than belts. Also, if a timing chain breaks, it’ll usually cause more damage than a broken belt and may result in the need for a complete engine transplant. A timing chain also features belt tensioners to keep it in place, but unlike those on a belt, the tensioners on a timing chain are controlled by the engine’s oil pressure. So, if your oil pressure drops for whatever reason, the tensioners won’t work properly, the timing will offset and the chain will ultimately fail.
How Long Does a Timing Chain Last?As we discussed above, the timing chain is a metal chain located inside the engine. It must be lubricated by the oil in the engine so that all of the components can work properly. Although some manufacturers suggest that a timing chain is built for the life of the car, most drivers can expect to replace the timing chain between 40,000 and 100,000 miles unless there’s another underlying problem. Timing chain issues are fairly common in high-mileage cars, so if you’re driving an older Chevrolet Cobalt or one with high miles, it’s important to understand the symptoms of a timing chain that is failing or going bad.
Signs Your Timing Chain Needs ReplacingOver time, the timing chain will wear out. If it fails completely, your Cobalt won’t run at all. For this reason, it’s important to be able to recognize signs that your timing belt needs to be replaced before it fails altogether. Several of these signs include:
1. The engine rattles while idling.Hearing strange sounds is a good indicator that there’s a problem in your motor. In normal conditions, your engine should have a smooth, consistent sound that lets you know everything is working as it should. However, if the timing chain becomes loose, it might cause a vibration in the motor, and you’ll hear a rattling noise. If this happens, it’s important to fix it as soon as possible before it completely breaks and causes more damage.
2. You find metal shavings in the oil.You probably already know that you should change your Cobalt’s oil and oil filter every 3,000 to 5,000 miles. Over time, oil separates as it is heated and exposed to the gasoline’s natural solvents. If your timing chain is failing, small metal pieces may fall off of the chain and end up in the oil pan. When you change your oil and see metal inside or you notice pieces of metal trapped in the filter, it’s a pretty good indicator that the timing chain is going bad.
3. The engine misfires.Over time, the timing chain might stretch, and it may skip gears, on the crankshaft or camshaft. This can cause the engine’s timing to fall out of calibration, and you’ll notice the engine misfiring. If this happens, it’s important to replace the damaged chain, because if it breaks, the loose metal can roll around inside the motor and result in costly and severe engine damage.
4. The car doesn’t start.If the timing chain is so loose that it’s no longer sitting properly on the gears, it won’t turn when the crankshaft is engaged. In other words, your engine simply won’t turn on. When this happens, it’s important to replace the timing chain before you attempt to start the car again. If you try to turn it on and the timing chain is broken or severely worn, you risk causing irreparable, costly damage to your engine.