Engine timing is one of the most critical yet poorly understood elements of maintaining a vehicle. Chances are good you know that your engine oil, transmission fluid, and even brake fluid need to be changed periodically. 

However, did you know that your timing chain will also need to be replaced and if it fails before you do, it could seriously damage the engine? In this guide, we’ll take a closer look at timing chains, the wear and tear they undergo, and how to prevent them from failing.

What Is a Timing Chain?

To operate and provide motive power to the transmission and then the wheels, your car’s engine must combust fuel and air. Doing so requires a complex dance of valves and cylinders. The timing chain (or timing belt on some smaller engines) coordinates this dance to ensure that valves open and close at the right time. 

The timing chain is affixed to the front of the engine in most cases (the right side in front-wheel drive vehicles), although this can vary. It is protected by a plastic cover that must be removed to access the chain. In many cases, the water pump is also located under the timing chain cover and, for that reason, water pump replacement is often part of OEM scheduled timing chain services).

The timing chain is located at the end of the camshaft. As the camshaft spins, its lobes open and close the cylinder valves that allow fuel and air to mix for combustion.

What Happens If My Timing Chain Fails?

If your timing chain breaks while the engine is running, it will immediately grind to a halt. It’s also likely that some valves will be bent as they contact the pistons (the timing chain prevents this from happening by keeping everything moving in time). Significant valve/piston damage will require costly repairs. 

If the chain breaks as the engine is turning off, damage is less likely, but you will not be able to crank the engine again until the timing chain is replaced. Without a functional timing chain, there is not enough compression for the engine to operate. 

How Often Should Timing Chains Be Changed?

Timing chains will last for a very long time. In most instances, they are not designed to be replaced until your vehicle reaches 100,000 or 120,000 miles, although this varies dramatically from manufacturer to manufacturer and vehicle type to vehicle type. High-performance engines put greater stress on their timing chains than lower-performance engines and will need more frequent replacements. Always refer to your owner’s manual or a trusted mechanic to ensure that you change the belt on time.

Signs and Symptoms of a Worn-Out Timing Chain

Timing chains are made of metal, but over time and through exposure to high heat and physical stress, they can suffer from wear and tear. Eventually, they will break. These chains look very similar to bicycle chains and are made with similar links. 

All it takes is for a single link to break and the timing chain is useless. In addition, chains can stretch over time and this can lead to them jumping teeth on the gears, which alters the timing of the engine and leads to a wide range of problems. 

Understanding the signs and symptoms that might indicate your timing chain is ready to be changed is the key to preventing outright failure. Below, we’ll explore some of the most common signs of a worn-out timing chain.

Rattling Noise

The most infamous sign that your timing chain is about to fail is a rattling sound coming from the engine. This is more prominent in certain types of engines, and in the early stages, it is almost undetectable from inside the cabin – you’re unlikely to hear it unless you’re outside the car, preferably with the hood open. Even then, the rattle in early-stage timing chain wear can be difficult to hear over the sound of other engine components. 

Check Engine Light

If your engine jumps time, the check engine light (MIL) will turn on. A mechanic will be able to pull the code and determine the cause. Often, this diagnosis is the first step in replacing the timing chain outside of regularly scheduled maintenance. For many people, the check engine light is the only warning sign that there is something wrong before the chain snaps. 

The challenge is that many problems can cause the check engine light to turn on, ranging from a loose gas cap to poor airflow into the engine. Some drivers assume that if they don’t notice the vehicle driving any differently, they do not need to worry about the check engine light. The problem with that way of thinking is that when new error codes are thrown, there is no way to tell because the light has stayed on. 

If your check engine light is on, have it checked. Most auto parts stores today can check generic codes, although you’ll still have to go to a dealership to diagnose proprietary codes. Many shops no longer charge to check the code, either particularly if you have the required repairs done at that shop.

Engine Misfires

As the timing chain wears, the metal can stretch. This may allow the chain to skip or jump to a different sprocket on the gear. When this happens, the engine will no longer be in time and you may experience a misfire. 

Misfires can sound like fireworks or gunshots, and they are very damaging to your engine. They are detonations – explosions – that the engine is not designed to handle. Prolonged misfiring can cause scarring and even lead to engine failure. 

Of course, timing chain problems are not the only causes of misfires. If you are experiencing misfires, it’s important to have the problem diagnosed and professionally repaired.

Lack of Acceleration/Performance

If you press the gas pedal and the vehicle responds sluggishly and does not accelerate as usual, it may be a sign that your engine timing is off due to belt wear. Again, other problems can also cause poor performance and a lack of acceleration, ranging from failed oxygen sensors to blocked air filters, so it’s important to have the issue professionally diagnosed.