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.
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.
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.
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.
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.
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.
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.
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.
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.
All metal engine components suffer from wear and tear over time and will slowly degrade. As the timing chain wears, small shavings come loose and will collect in the engine oil. The best way to determine the presence of these shavings (or finings) is to check during an oil change.
In some cases, holding a magnet in the stream of old oil or on a probe into the oil pan will collect visible metal shavings. This should be considered a warning sign that your timing chain is seriously worn and needs to be replaced.
If the timing chain snaps, your engine will not start. However, there are dozens of other potential reasons for an engine not to crank, ranging from a dead battery or failed alternator to damaged electronic components.
If the timing chain breaks while the engine is running, the engine will stop immediately and will likely bend valves and damage the pistons. The timing chain can also flail around inside engines and the loose ends may cause additional damage. It is not uncommon for this to damage the engine beyond repair.
While every timing chain will eventually need to be replaced if you drive the vehicle enough, there are certain situations and conditions that will accelerate the wear and tear your chain experiences. In this section, we’ll break those down for you to help ensure that you’re able to maximize chain life and delay any potential damage.
Engine oil is responsible for lubricating the moving parts of your engine. That includes the timing chain and the gears/sprockets that it attaches to. If you don’t change your oil on time, this can cause wear and tear and shorten the lifespan of your timing chain.
The problem is that as oil ages, it is exposed to high heat and naturally-occurring detergents from gasoline. These reduce oil’s ability to lubricate (called viscosity). Your engine oil will also become thicker over time and will coat less and less. Eventually, the timing chain may be left unprotected from metal-on-metal wear. When this occurs, you can expect wear and tear to accelerate dramatically.
Another problem is using the wrong engine oil in your car. While all engine oil types perform the same function, they are not the same. You should use the oil weight recommended by the automaker for your specific model. This information should be available in the owner’s manual or on the oil filler cap under the hood.
Engine oil is rated by weight, which can be misleading for some. It’s a measure of thickness/viscosity. For instance, 0W20 flows like 0-weight oil (very thin) during the summer and like 20-weight oil in the winter (thicker). In comparison, 5W20 flows like 5-weight oil in the summer and 20-weight oil in the winter. Using oil that does not have the right flow characteristics for your engine can mean starving the timing chain of oil or coating it in oil that’s too thick and reducing its performance.
Always use the automaker’s recommended oil for your vehicle. If you’re unsure what it is, ask the mechanic at your next oil change.
The more work the engine must do, the more wear and tear moving parts like the timing chain will incur. This is especially true when it comes to towing or hauling heavy loads. The more weight the engine must move, the harder it must work. This adds stress and load to the engine and the timing chain. In some cases, you may even hear the chain rattling when the engine is under a heavy load, particularly if the chain is nearing the end of its life.
However, don’t assume that if you don’t hear a rattle your chain is fine. Always follow the automaker’s recommended schedule of services, particularly when it comes to replacing your timing chain.
Like the engine’s serpentine belt, the timing chain also has a tensioner. Its purpose is self-explanatory – it provides tension to keep the chain taut and prevent it from jumping. There are two types of tensioner used today: hydraulic and spring-loaded.
If the tensioner fails, it will no longer hold tension on the timing chain. Depending on the situation, this can lead to a rattling sound, but it could also allow the chain to jump and cause the engine to shift out of time. In that case, you may experience backfires and the check engine light will usually come on.
Depending on the situation, this may also cause your engine to idle rough, or put your car into “limp home” mode. This is a security feature that reduces the load on the engine by cutting off nonessential systems, like air conditioning, as well as limiting the speed of the vehicle.
The simplest way to determine if the timing chain needs to be replaced is to take your car to a trusted mechanic. They can use a stethoscope to listen to the rattle, check tappet operation, and verify that the problem is indeed the timing chain.
It’s also important to ensure that you always follow the manufacturer’s specified service schedule, particularly higher-mileage services like the timing belt/water pump service. This schedule of services should be available in your owner’s manual, but you can also ask a trusted mechanic.
Your vehicle’s timing chain is a critical component. Without it, the engine will not run. Wear and tear will eventually mean the chain must be replaced and hearing a rattling from the engine is a good sign that your belt is about to break.
If you suspect that your timing chain needs to be replaced, visit a trusted mechanic as soon as possible.
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