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Timing Belt vs Timing Chain

A bit of timing belt history

Toothed belts were first developed for textile mills in the early 1940s. Naturally as vehicles developed with “newer technologies” so did the application of existing technologies. Timing belts were used for automotive application until 1954 when they entered the racing scene. From then on, the timing belt became a common design among all the vehicle manufacturers. Continue reading to learn about timing belts, timing chains and the pros and cons of each of them.

What is a timing belt?

A timing belt is a ribbed belt on an internal combustion engine that is made from rubber. It connects the camshafts with the crankshaft, and often the water pump. It is used to keep the camshafts and crankshaft synchronized with specific reference points or timing marks, also referred to as “in time”. Timing marks are extremely important as they ensure an engine is properly synchronized to run.

Why is it called a “timing belt”

A timing belt naturally got its name from its purpose. It’s simply a belt that keeps the engine “in time”, therefore it is referred to as the “Timing Belt”. A timing belt can also be referred to as a “drive belt”.

Where is a timing belt on an engine?

Most engine designs include a single or multiple camshafts on the top of the engine and a crankshaft on the bottom. The Timing belt is usually located at the FRONT of the engine under a plastic cover that is relatively easy to access. It is important to not though that the timing belt is not lubricated in any way. It sits on the outside of the engine away from all the oil and other engine fluids.

Because timing belt cover is usually easy to access, a trained automotive technician can quickly determine if it is worn. The timing belt cover is often removed to check the timing of the engine.

What does the timing belt do?

The timing belt is usually connected to the following components:

  • Ribbed camshaft sprocket
  • Ribbed water pump sprocket
  • Ribbed crankshaft sprocket
  • Smooth idler pulley
  • Smooth timing belt tensioner

In many cases there are multiple camshafts which mean there are multiple camshaft sprockets, but usually the timing belt will only be wrapped around the above 5 components.

Ensuring the engine timing is correct is vital to the engine running. A timing belt is what keeps the engine components synced properly. The crankshaft spins and everything that the timing belt is wrapped around spins as well at the same time.

You can see this in action with the visual below:

Does a timing belt wear out?

Yes. Timing belts do wear out. Manufacturers do thorough testing with their products, and it is best to follow the factory recommendations regarding timing belt change intervals.

I have seen personally where a vehicle reaches its recommended service interval. The recommendations were ignored and a few thousand miles down the road, the timing belt broke, and it caused catastrophic damage in the engine. I have personally seen this many times. There are reasons the vehicle manufacturers put those specific date intervals on service recommendations. It is best to follow those or even do preventative maintenance.

Signs of wear on a timing belt

Timing belts do show signs of wear both visually when looking at them and when reading the vehicle data using a professional scan tool. When a timing belt is starting to wear out, you’ll often see little hairline cracks on the smooth part of the belt.

If you can remove the belt and bend it around a little bit, chances are you’ll see cracks on the belt teeth themselves. Vehicle mileage, age, scan tool data and the visual wear on the belt, give a good indication of whether you should change it or not. In most cases, preventative maintenance is the best answer.

How long does a timing belt last?

Timing belt quality has been improving over the years and every manufacturer is going to have a different recommended service interval. BUT, if I had to pick safe change interval number, I would say you should replace your timing belt every 100,000 Miles or 160,000 Kilometers.

What does it cost to replace a timing belt?

The cost of replacing a timing belt will vary from vehicle to vehicle. Some area very easy to access and don’t need special tools, others are very difficult to access, and you need professional tools that can be very expensive.

I have consistently seen timing belt changes anywhere from $1000 – $3000. A timing belt replacement is often combined with the tensioner, pulley and water pump because of the work involved to access the belt. Those other components are wearable items, and you have everything open at the same time. It just makes sense to replace it all together.

Can I replace my timing belt myself?

Of course, you are able to, but would you want to? Timing belt replacements often require special tools to make sure the timing marks are all lined up, you have to torque all the bolts and nuts to specific specifications and the process isn’t always clear on how to actually do the job. This is often one of those times where it is best to let someone handle it who has done many of these before, has the proper equipment and also has the liability covered in case something goes wrong.

Timing belt pros and cons

All in all a timing belt is a great option for use on an internal combustion engine. There are benefits to cost of manufacturing and serviceability of timing belts. They are easier to service and are often more accessible in the vehicle. As vehicles have developed though we have put a lot more demand on the engines and as demand changes, so do the components and requirements of those components. Timing belts are great for simple engine setups but when more and more rotating components are getting added to the engine for operation, it makes more sense to move to something like a timing chain. Keep reading to learn about timing chains and how they differ from a timing belt.

What is a timing chain

A timing chain is exactly what it sounds like. It is like a timing belt in its function. It connects the camshaft sprockets to the crankshaft sprockets, it has a chain tensioner, and it is used to keep the camshafts and crankshaft synchronized as they rotate around and around. The biggest and most obvious difference is it is a metal chain instead of a rubber toothed belt.

Think of it like a bicycle. The sprockets have teeth on them as opposed to ribs. On a bicycle, the chain goes around sprockets that have pointy teeth that keep the chain in place. This is the same with a vehicle timing chain.

Why is it called a timing chain?

Naturally as the development of the “Timing Belt” evolved, the requirements for the “drive belt” changed and new materials were tested. In this case it was a chain. The chain served the same purpose as the timing belt and was therefore name the timing chain.

Where is the timing chain on a vehicle?

A timing chain is often located on the front of a vehicle’s engine, but it is contained inside the engine block. The timing chains are not easily accessible by removing a simple cover because the engine is sealed to keep the engine oil in. In some cases the timing chain is on the back of the engine. This isn’t a good or bad thing, it is just different but still serves the same purposes.

What does the timing chain do?

The timing chain connects the toothed camshaft sprockets (usually multiples) to the toothed crankshaft sprocket to keep the camshafts synchronized with each other and also the crankshaft. Often when a vehicle engine uses a timing chain, the engine is considered an “interference engine”. This means the camshafts or crankshaft components cannot be rotated without the correct timing because it will cause significant damage to the engine.

Does a timing chain wear out?

Yes. Eventually timing chains can wear out. The wear on a timing chain is often due to poor vehicle maintenance though, or manufacturer defects in a part. There are other components that will likely wear out sooner such as the timing chain guides and the timing chain tensioner, if any of those start to wear, they should all get replaced together along with the timing chain.

Signs of wear on a timing chain

Timing chains are more difficult to see wear on, and in theory they shouldn’t wear at all. Timing chains, because they are located inside the engine, are exposed to the engine oil. This is really important because the engine oil acts as a lubricant for the timing chains. In theory the oil creates a barrier between the metals preventing wear and allowing for heat dissipation. Unfortunately due to lack of proper maintenance, when engine oil gets dirty or starts to break down, it can allow that wear to happen on the timing chain.

How long does a timing chain last?

In theory a timing chain should last as long as the vehicle. If the oil is changed regularly according to the manufacturers specifications, you shouldn’t have issues with the timing chain.

Cost to replace a timing chain

The cost associated with replacing a timing chain is often very expensive. There are other components that need to be changed along with it and I have seen timing chain replacement costs anywhere from $2000 to $8000 depending on the vehicle.

Can I change the timing chain myself?

Timing chains always require special tooling. You usually have multiple spring-loaded camshafts, and it is impossible to replace them properly and accurately without the proper tooling. In many cases you have to remove the vehicle’s engine to replace the timing chain. While you can get the parts yourself and if you have the tools and know-how, of course you can replace the timing chains yourself. Most people don’t have an engine hoist and specialized equipment though, so when it comes to replacing your vehicles timing chains, it is best to let a trained professional handle it.

Pros and cons of timing chains

Timing chains came on the seen in the early 1990s and have been a great evolution in terms of managing vehicle timing. Chains are generally strong, so you can have more components and accessories being run by timing chains. The fact that they are being lubricated by the engine oil means that they generally last a lot longer than a standard timing belt. With that said, they are harder to service and are more costly when service is needed.

Summarize the differences between a timing belt and a timing chain

  • Timing belts sit outside the engine and are covered by a plastic cover. Timing belts are usually easier to service and don’t always require special tools to set the timing properly.
  • Timing chains live inside the engine and are bathed in oil. Timing chains are not easily serviced and require special tools to like up the camshafts.
  • Timing chains typically last longer than timing belts and can handle running more rotating components on the engine.
  • Timing belts are typically quieter and more affordable for manufacturing.

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