A vital part of any internal combustion engine, the timing belt is critical in ensuring that the various parts of the combustion system run "in sync" with one another. A worn or failing timing belt can result in serious (expensive) damage to your engine, so making sure it's replaced at the first sign of trouble is important. Here we take a look at the role the timing belt plays, as well as how to detect when it's beginning to give way. Finally, we consider the costs involved when a timing belt needs to be replaced.

What is a timing belt?

The timing belt is literally a band made of rubber, that connects the camshaft and the crankshaft. Also known as a cam belt, the timing belt ensures coordinates the action of the camshaft (the camshaft is responsible for opening and closing the valves of the engine at the right points during the combustion cycle) with the crankshaft (the crankshaft is responsible for converting the vertical action of the rods into a rotational movement, which then travels through a flywheel to the transmission). If the timing belt is stretched or worn, the camshaft and crankshaft cease to work together. This has a significant impact on performance. In addition, it also puts considerable stress on other parts of the engine, potentially leading to total engine failure if not dealt with promptly.

It's important to note that most modern cars are now fitted with a timing chain rather than a timing belt. The timing chain carries out the same function as the timing belt (connecting the camshaft to the crankshaft), but is made from metal links, rather than rubber. The result is a mechanism that lasts far longer than the rubber timing belt. In most cases, a timing chain will last the lifetime of the engine. The only downside of a timing chain in comparison with a timing belt is that it can be slightly noisier when the engine is in use. Your driver's manual will tell you if your vehicle has a chain or belt, if you're not sure.

Signs of a bad timing belt

Given the enormous damage that a timing belt that's not performing optimally can cause, it's important to know when to change timing belt parts. Luckily, there are several signs that a timing belt is causing problems before the situation becomes critical. Here are some of the key symptoms of a vehicle that has a worn or broken timing belt:

  • The engine sounds rocky. If it sounds as if the engine is working extremely hard when the driving conditions and speed would suggest otherwise, the timing belt could be the problem. You may also hear backfiring.
  • The smell of burned rubber. Obviously, if a timing belt has slipped a little, or has worn unevenly, it could likely heat to an abnormally high temperature, causing the unpleasant burned rubber odour.
  • Engine shakes and an uneven, strained turnover. A slipping timing belt will result in an engine that sounds choppy! If your engine really does sound as if it's on the way out, especially if the noise is accompanied by shaking or vibration, the timing belt is an obvious suspect!
  • A number of odd engine noises whilst the vehicle is being driven. Expect anything from squeaks to bangs, pops, rattles and more. All these noises are a sure sign that your engine isn't working correctly, which means it's time to get the timing belt checked as a matter of urgency.
  • The vehicle won't start. If the timing belt has snapped completely, or become so worn as to be inoperable, the engine will fail completely.

Remember that if left unchecked, a failing timing belt can cause an enormous amount of damage to your engine. If your engine is sounding rough, it really is important to get it checked out promptly with a view to checking the timing belt.

When should a timing belt be replaced?

Obviously, if you notice any signs that suggest the timing belt is slipping or has become worn, it's important these are checked out by a qualified mechanic to see if it is the timing belt that's at fault. If it is, it's definitely time to invest in a fresh timing belt. During the engine dismantling process, the mechanic may also check for other signs of wear, as the timing belt may not be the only issue. In addition, if the belt has been left running poorly for a while, other parts of the engine will have been damaged and need replacement.

If you don't notice any signs of timing belt failure, the belt should still be replaced after somewhere between 100,000 km and 160,000 km miles of driving. Your driver's manual should give you an approximate guide for the most appropriate replacement time, as there is considerable variation between vehicles.

Cost to replace a timing belt

Unfortunately, the cost of replacing a timing belt can be quite steep. The bulk of the cost is related to the amount of engine dismantling (engine stripping) that needs to occur before the belt can be reached. The timing belt is deep inside the engine, which makes reaching it a challenge. The actual timing belt price is fairly modest, but combined with labour, it's not unusual to pay as much as $1,000 or more.

The price varies depending on the make and model of vehicle, as well as the difficulty involved in stripping the engine. Detailed below are some average timing belt replacement costs for a selection of vehicles:

  • Holden Captiva - $400 - $1,200
  • Volkswagen Crafter - $900 - $1,100
  • Mitsubishi 380 - $800 - $1,500

If you want to save money on your timing belt replacement, it's obviously worth getting a quote from several different garages to find the cheapest. Check their reviews to ensure they're also likely to do a good job! You may also have a mobile mechanic in your area, who can often offer a more competitive price than what you'll obtain from a conventional garage.

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Jordan Ballard

Jordan Ballard

Automotive Content Editor

Jordan is a car finance and automotive industry specialist at Only Cars. With over 20 years of experience with frontline and management roles in sales, finance and other areas, Jordan has an incredible understanding of the automotive industry. As Automotive Content Editor, Jordan loves sharing his passion for cars with the Only Cars audience.