How to check and change your cambelt

Whatever model of car you have, it will have a cambelt (also called a timing belt), but you may not know what this car part does. Here, we'll take you through what a cambelt is, when you need to replace it, and how you can do it yourself. It's vital to be able to check, maintain and replace this essential part of your car engine, and this guide will give you all the information you need to make sure it's functioning correctly.

In this guide, we'll start with some basic understanding of a cambelt, before outlining how you can replace your cambelt yourself, and how to check your timing belt to see whether your vehicle needs a new one.

In this guide we'll be covering:

• What is a cambelt and what does it do?
• What is the difference between a cambelt and a cam chain?
• Why does the cambelt need replacing?
• When does a cambelt need replacing?
• How to tell if your cambelt needs changing
  • Your car won't start
  • The engine is making noises
  • The cambelt looks worn
• What happens if the cambelt breaks?
• How much does a cambelt change cost?
• How do you replace a cambelt?
  • Find the right timing belt for your car model
  • Replace your gaskets and adhesive
  • Disconnect the battery
  • Take out the alternator belt
  • Remove anything else in front of the timing belt
  • Check the alignment of the cambelt
  • Remove the cambelt itself
  • Position the new cambelt
  • Put the engine back together
  • Test drive your car

What is a cambelt and what does it do?

The cambelt, also called a timing belt, is a belt made out of sturdy materials like Kevlar and polyurethane. It can be confusing to understand exactly what a cambelt does, but essentially, it regulates the way your engine works.

It controls the opening and closing of the valves to the cylinders of your engine. This ensures that your engine's combustion happens correctly. While the cambelt is controlling the valves opening, the crankshaft simultaneously moves the pistons up and down. It's important that your cambelt is working correctly, and the crankshaft is working in sync with it, as it regulates your car's combustion to keep it running smoothly.

What is the difference between a cambelt and a cam chain?

You might have heard of both a cambelt and a cam chain, but these two parts perform different functions and it's useful to understand what they both do. The most obvious difference is that a cam chain is made out of metal, which is a contrast to the plastic or synthetic cambelt. The cam chain in your vehicle is located inside the actual engine, and therefore is lubricated by the engine oil. In contrast, cambelts are located outside the engine.

However, some manufacturers have begun using new parts called 'wet belts', and these are like cam chains, and run inside the engine. Cam chains often don't need to be replaced as often as cambelts, because the metal they are made of is stronger than the materials used to construct cambelts. This is also because they are lubricated by engine oil, whereas cambelts can get dry and crack over time.

Why does a timing belt need to be replaced?

Like a lot of parts in your car, the cambelt will eventually wear out. The reason it's particularly important is that it can obstruct the combustion in your engine if you don't keep it maintained and replaced regularly. If the cambelt snaps or tears, then it can cause a lot of damage to your engine.

Here’s what can happen if your cambelt snaps:

• If it breaks while you are driving, it's possible for the engine to seize up, and this can cause the steering and the breaks of the vehicle to cease working.
• The pistons can hit the valves in the engine's cylinders, which can damage them.
• A non-interference engine will usually suffer less damage, but there will still be some.

When to change a timing belt

Cambelts need to be replaced, as they wear out over time. But there's no exact length of time to wait before you replace one. Different models of car will need their cambelt replacing more frequently, while others will have them last for longer. It also depends on how much you drive your car.

Commonly, your vehicle's manufacturer will recommend changing the cambelt after either a certain number of years, or a certain number of miles driven. This might be in the range of 40,000 – 100,000 miles driven, or four years. Ask either your manufacturer or the dealer where you bought the car, and see if they have specific advice on the model that you drive.

How to check if your timing belt needs replacing

It's extremely useful being able to spot the signs in your cambelt that show you it needs replacing. Make it a habit to check these things regularly, so that you can be assured that it is working. It also means that you will be able to replace it quicker, prior to it causing any damage to your engine by breaking.

Your car won't start

If your car fails to start unexpectedly, then it might be due to an issue with the cambelt. This is because if the cambelt breaks, it means that the cam shaft won't be rotating when the crankshaft turns, leading to the car not being able to start. It's best if you keep up with regular checks on your vehicle to make sure that this doesn't happen and disrupt your commute, holiday, or shopping trip.

The engine is making a rattling noise

The other key sign to look out for is whether there are any strange noises emitting from your engine. If your cambelt is about to fail, you might be able to hear a friction sound coming from your engine. You should call a mechanic if you hear this coming from your car, as it's likely that the cambelt needs replacing and might be about to snap.

The cambelt looks worn

Perhaps the easiest way to check if the timing belt needs replacing, is to take a close look at it. A clear sign that the belt is becoming worn is that it has become glossy and smooth on the underside — it shows that the rubber of the cambelt is getting worn, and so it won't be as flexible as it needs to be.

If the belt is cracked or torn, then it needs to be replaced straight away. You can also do a pressure test — try pressing a screwdriver or your fingernail into the rubber of the cambelt, and if it doesn't leave an indentation then the belt has become too hard and needs replacing.

What happens if the cambelt breaks?

If you're unlucky enough to have your cambelt break completely, the type of engine you have will determine how much damage occurs. Engines are split into interference engines and non-interference ones. An interference engine is a kind of 4-stroke internal piston engine where one or more valves in the fully open position extends into an area where the piston might travel. But in a non-interference engine, the piston doesn't travel into any part where the valves open.

Interference engines use the timing gears, belts, or chains to stop the piston from striking the valves — it does this by ensuring that the valves are closed when the piston is close to the top centre area. So, in an interference engine, a cambelt breaking can cause a lot of damage to the valves and other engine parts. A non-interference engine typically doesn't get as damaged.

How much does a cambelt change cost?

The cost of having a mechanic change your cambelt will vary depending on the model of your car, but it can range from £200 up to £1,000 for certain replacements. However, more typically, cambelt changes cost around £300-£400. This is because changing the cambelt involves taking apart pieces of the engine and putting it all back together again.

This can take a few hours, which means that you need to pay for the labour costs of the change. Many people choose to do a cambelt replacement themselves, because it's possible to find the cambelt itself for around £100, which is much more cost effective than paying for a garage to do the change.

How to replace a timing belt

So, if you've decided to take the plunge and change your cambelt yourself, what can you expect? It can feel a bit overwhelming at first to contemplate taking your engine block apart, but once you've done it once, you'll be able to save yourself some cash whenever your timing belt needs changing.

Here, we'll take you through how to change your cambelt, complete with a video that you can watch while you read through our instructions, so you can be sure you know how to make a start.

1. Find the right timing belt for your car model

Before you get to taking apart the engine, you'll need to acquire the right timing belt for your vehicle. The owner's manual of your car will show you which type of cambelt you need, and then you can look at car part suppliers for one that matches.

If you don't have the manual, or it doesn't give you this information, take your car to your nearest car parts dealer, and tell them the make and model of the vehicle. From this, they should be able to find the right car part. You can also use the GSF search tool, where you can type in your car's registration number or mode, and find the perfect timing belt to fit the vehicle.

2. Replace your gaskets and adhesive

Since there has been some decay or damage to your timing belt, it's wise to also replace your gaskets and gasket adhesive. The car parts supplier that you get your new cambelt from should know what kind of gaskets you need too, and then you'll be ready to get started.

3. Disconnect the battery

The first thing to do when you begin the process of replacing the cambelt is to disconnect the car's battery. This is very important, as not disconnecting it will result in electric shocks as you take apart the engine.

To do this, disconnect the negative battery cable from its terminal — you don't, however, need to take the battery out entirely as breaking the continuous circuit is enough to make sure you won't get a shock. If you think there might also be a problem with your battery, you can check out our guide to choosing, charging and changing car batteries.

Remember that you might need to enter a code to regain access to your electrical devices such as radios, Sat-Navs, and anything else that you've set up to run off your car's electricity. This is because those devices will reboot and need logging into again. Write down any codes you'll need prior to disconnecting the battery if you're liable to forget them.

4. Take out the alternator belt

The alternator belt is a belt that's smaller than the timing belt and located on top or in front of the timing belt. Loosen the nuts to create some slack in the belt, and then remove it. In some models of car, you will also have to take out the serpentine belt. If it's not in the way, it can be left in, but if it's obscuring you getting into the engine, remove it.

Be careful not to remove any pressurised fittings, as this will cause other problems within the engine. For more details on what an alternator is, and what it does within your car, read our guide on alternators.

5. Remove anything else in front of the timing belt

It will be easier to remove your cambelt if you first take out anything that is in the way. Things like the power steering pump, and the air conditioning compressor will often be obstructing you being able to reach the cambelt, so these can be taken out. If your vehicle has a distributor cap, this will also need to be taken out, which will require removing both screws and clips.

However, you might not need to do this, as many modern cars have electric ignitions, and therefore aren't built with distributors. If you are confused about how to find the distributor, or whether your vehicle has one, check your owner's manual, which should contain these details.

6. Check the alignment of the cambelt

Look at the timing marks and rotate the crankshaft so that the marks align with the 0 that you can see on the timing scale. This should be done with a spanner. You'll need to remove all the screws and bolts that keep the cover of the cambelt in position. Then, remove the cover. Check that the crankshaft and the camshaft marks are aligned with each other. There will be dots and lines on both of the shaft heads that need to be lined up.

7. Remove the cambelt itself

Now you can start removing the timing belt. Before you do, it might be helpful to take a picture of it in your car, so you can be sure to get the new one in the right position. Then, make sure that there are no leaks (either oil or water) around where you're working, and loosen the bolts which keep the belt tensioner in place. This will create slack and allow you to slide the timing belt off and remove it.

8. Position the new cambelt

Place the new cambelt where you'll need it to be and make sure it's positioned exactly the right way before you move forward any further. Use the photo you took or look at your model's owner manual to make sure that you have positioned the cambelt correctly.

9. Put the engine back together

Now that you have positioned the new cambelt, you can put the rest of the engine back together. Take all the parts that you have taken out, and add them back into the engine, replacing them so that they are all positioned in the same way that they were prior to you taking them out. You should replace the parts in reverse order to the way you took them out.

10. Test drive your car

Now that you've put the engine back together, it's time to check that you've done everything correctly, and that the new cambelt works. The best way to do this is to give your vehicle a little test drive. Take the car onto some quiet roads and test whether it drives smoothly. If this goes well, then you can rest assured you have changed the cambelt successfully!

By following these steps, you should be able to change your cambelt and save yourself some money on car maintenance. To find the right cambelt for your car, try out our search tool that allows you to find the right car parts for your vehicle.

If this is the first time that you have changed a cambelt, it's a good idea to use one of our timing belt service kits, which contain all the things you'll need to make this sometimes daunting job a bit easier. It comes with a new timing belt, tension pulleys, and an idler, so it can really cut down on the time that the job takes. Here at GSF, we also offer the full range of timing belt parts to allow you to carry out repairs to your vehicle.

Just type the registration of your car into our website, and we'll put together a kit of all the right parts, to get you on the way to a new cambelt. By using our tips and following these key steps, you'll be able to maintain, check, and replace your timing belt, preventing damage to your vehicle and keeping it running smoothly.