How does a cambelt or timing belt work?
A cambelt, also known as a timing belt, is a crucial part of your car’s engine. Think of it as the maestro of an orchestra, making sure everything runs in perfect harmony. The cambelt synchronises the movement of the engine’s crankshaft and camshaft, ensuring that the engine’s valves open and close at the right times during each cylinder’s intake and exhaust strokes.
When the engine runs, the crankshaft turns, which in turn drives the cambelt. The belt then rotates the camshaft, which controls the opening and closing of the engine's valves. This precise timing ensures that the engine runs smoothly and efficiently, avoiding collisions between valves and pistons.
Over time, the cambelt can wear out due to the constant stress and heat it endures. If it breaks, the engine’s timing can go haywire, leading to severe damage. That’s why it’s essential to replace the cambelt at the intervals recommended by your car’s manufacturer to keep everything running smoothly.
In some modern cars, a timing chain is used instead of a belt. The chain serves the same purpose but is typically more durable, although it might still need replacement eventually.
What does a cambelt change or timing belt replacement involve?
A cambelt change job involves several key steps to ensure your car's engine runs smoothly and efficiently. Here’s a simplified overview of the process:
- First, the mechanic raises the car using a lift or jack to access the engine more easily.
- The mechanic then removes any necessary components blocking access to the cambelt, such as engine covers, drive belts, and in some cases, parts of the engine itself. The timing belt is hidden from view and protected by a cover in the vast majority of cases.
- Next, the old cambelt is carefully removed. The mechanic will take note of the timing marks on the engine to ensure the new belt is installed in the correct position.
- Before fitting the new cambelt, the mechanic inspects related components like the water pump, tensioner, and idler pulleys. If any of these parts show signs of wear or damage, they are typically replaced at the same time to avoid future issues.
- The new cambelt is then fitted, making sure it is aligned correctly with the engine's timing marks. This step is crucial as improper alignment can cause severe engine damage.
- The mechanic then adjusts the belt tension according to the manufacturer's specifications to ensure it operates correctly.
- Once the new belt and any other replaced components are installed, the mechanic reassembles any parts that were removed to access the cambelt.
- Finally, the mechanic runs the engine to check that the new cambelt is working properly and that the engine timing is correct. This ensures the engine runs smoothly and efficiently.
This job requires skill and precision, which is why it’s best done by a professional mechanic.
Under no circumstance should a timing belt be put back on once it has been removed, no matter how recently it was done. Any small nicks or damage to the belt during the process could be catastrophic - so no, for the cost of the belt itself its not a risk that any mechanic would take.
What happens when a timing belt breaks?
There is very little pre warning that a timing belt is about to break, it will simply snap. This can occur at any time, from initial startup to cruising on the motorway. Whatever the circumstances, the chances are that your engine's pistons will collide with valves that are operated by the camshaft. The result of this collision depends on a number of factors, but the valves, rocker arms, camshaft, pistons, even the cylinder head itself etc all could suffer damage.
The only way to fully understand what damage has been caused is to remove the cylinder head from the engine and physically see what the resultant collision has caused.
Therefore, if your timing belt has snapped, we cannot quote how much it will be to repair the damage, as we simply will not know at that stage. What we can quote for though, is the work required to strip off the cylinder head in order to provide a quote on the damage caused. If this is the case, you always contact our Mechanics in Residence team for a custom quote.
How do I know whether I need a cambelt repair or replacement?
In almost all cases, the cambelt will need to be replaced as it can’t really be “repaired”. Here are some things to look out for:
If you hear a ticking noise coming from the engine, it might be a sign that the cambelt is wearing out. This noise can indicate that the belt is not functioning properly and may need replacement soon.
If your engine misfires or runs roughly, it could be due to a failing cambelt. This happens because the timing of the engine's valves is off, which can be a direct result of a worn or damaged cambelt.
If you experience oil leaking from the front of the motor, it could mean that the cambelt cover is loose or damaged, which can cause the cambelt to wear out more quickly. This might need repair or replacement.
If the car won't start at all, and you’ve ruled out battery issues, a broken cambelt could be the cause. This is a serious issue and requires immediate attention, often leading to a full replacement.
If you notice the engine light on your dashboard comes on, it can be a sign of many issues, including problems with the cambelt. It’s important to get it checked by a professional to avoid severe engine damage.
Lastly, if your vehicle has hit the manufacturer’s recommended mileage for cambelt replacement, usually between 60,000 to 100,000 miles, it’s wise to get it inspected or replaced to prevent unexpected failure.
What does a cambelt change cover?
Unless otherwise stated, a ClickMechanic quote for your timing belt replacement will cover;
Timing Belt Only Engines
- The cost of the timing belt kit (Belt, Tensioner and Guide(s) where appropriate, usually INA, Dayco or Gates, depending on availability
- Coming to you
- Fitting of the parts
- Disposal of the old parts (unless you request to keep them)
- VAT (if applicable)
- 12 months parts and labour warranty
Timing Belt and Water Pump Engines
- The timing belt kit (Belt, Tensioner and Guide(s) where appropriate, usually INA, Dayco or Gates, depending on availability
- The water pump
- Engine coolant/antifreeze
- Coming to you
- Fitting of the parts
- Disposal of the old parts (unless you request to keep them)
- VAT (if applicable)
- 12 months parts and labour warranty
Should I book a water pump replacement and auxiliary belt replacement and cambelt change at the same time?
If the water pump is driven by the timing belt, then it is also an important bearing and cog on the circuit. Therefore it is considered as vital as the guide(s) and tensioner and must be replaced. Mechanics will not consider replacing a timing belt that has a water pump on it, without changing it.
The other reason is that should the water pump fail, then the whole timing belt job has to be done again with a new belt.
If the water pump is not on the timing belt, there is no need to do so, however, if you wish, we can of course do it, but there is little cost saving in doing so.
The auxiliary belt will need to be removed to carry out the work, so it is an ideal time to change it for just the cost of the belt as there is no additional labour. It isn’t imperative though, so you do not have to.
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Frequently asked questions about cambelt change, repair & replacements
Read our answers to questions about cambelt change costs, symptoms and more.
What does a timing belt (cambelt) do?
The timing belt (or cambelt) is a toothed, strengthened rubber belt used to rotate the camshafts at the correct time with the pistons, hence “timing belt”.
What does a timing belt (cambelt) replacement involve?
- Mechanic will remove or loosen the components required to gain access to the cover. This may also involve removing a wheel as well, so do not be alarmed!
- Mechanic will then lock the camshafts and crankshaft in place with timing pins, before removing the old belt and associated guides and tensioner.
- Mechanic will also drain the cooling system and remove the water pump if it is driven by the belt
- Once a cleanup has been done, the mechanic will renew the components and finally fit the new belt.
- Any components removed will be put back in place, the cooling system replenished and the engine started and tested.
- The cooling system will then be bled of air and the vehicle road tested.
Can I replace the cambelt myself?
Unless you are a qualified mechanic with the required skills, training and equipment to do the job, we strongly recommend a cambelt change is only carried out by a professional mechanic. ClickMechanic can help get you a vetted and local mechanic to carry out the work. Just enter your postcode and your car's registration number at the top of this page and select the work needed to get an instant fixed price up front.
What are the signs of a bad timing belt?
Sadly in 99% of cases you will only know if there is an issue with the cambelt when it breaks! This can occur at any time, at any speed and usually at the most inconvenient time and place. This is why manufacturers give recommended replacement intervals, both in terms of age and mileage. It is preventative maintenance that should never be overlooked.
How long will a cambelt replacement take?
On average, cambelt change times can range from 1.5 to over 5 hours with an average of 2.7 hours. The time that the job takes will depend on a number of factors, like your vehicle's make and model, year, as well as other factors. Select your car at the top of this page for information on job time and cost for your vehicle through ClickMechanic.
How often should a Cambelt be changed?
The lifespan of a cambelt is generally between 5 to 8 years, depending on the manufacturer. Every vehicle which has an engine that uses a timing belt, needs to have this done as part of the scheduled maintenance. Therefore always remember to replace the timing belt when stipulated in the car manufacturer's service schedule.
If your car is around the age of normally needing a scheduled cambelt change, and you have no record of the job ever having been done, it would be wise to get the belt replaced rather than chancing it.
When should you change your Cambelt?
Each manufacturer will give a recommended replacement interval for the timing belt on its vehicles. This information is usually available in the Owner Handbook, however if you do not have this in your possession, we are happy to advise accordingly.
If you have purchased a second hand vehicle and it has no timing belt change history, such as a garage invoice, then it is important to err on the side of caution and have it replaced as soon as possible,
Do I need to change the water pump when I change the timing belt?
On many engines, the water pump is driven by the belt as well. If this is the case, it is imperative to have it replaced at the same time. There are two reasons for this, firstly, the water pump is a pulley and bearing that forms part of the circuit the belt travels around and should it fail, then the belt will come off and that is the same as it breaking. Also, water pumps are prone to seizing, which again will break the belt.
The second reason is that should the water pump fail (and not damage the belt etc) and require replacing, then the timing belt would have to be renewed at the same time, so its best to have a new one fitted as a preventative course of maintenance.
Most mechanics will not carry out the work unless the pump is replaced in the situation as they know the consequences!
At what mileage should the Cambelt be changed?
If your car is fitted with a timing belt (and not a chain), then the replacement needs to be carried out at the time stipulated by the manufacturer. This could be between 5 - 7 years or 60,000 to 100,000 miles. So in reality, it is a very common jobs as all cars equipped as such need to have this done.
What happens if you don't change a Cambelt?
If the cambelt has not been replaced as per the maintenance schedule stipulated by the manufacturer the belt will be at risk of failure.
What happens if Cambelt breaks while driving?
If the cambelt should break, then the pistons will continue to rotate momentarily and collide with the valves in the cylinder head as they are no longer in the correct position as the camshaft will have stopped turning. The result of this collision can result in severe damage to the engine, from bent valves, to broken engine internals. It can even destroy an engine completely.
Unfortunately there are very few engines where you will get away with it breaking and just require a new belt although a few manufacturers have intentionally engineered weak points in the rocker arms to reduce the damage should it occur.
How do I know if my Cambelt is worn out?
You cannot generally check to see if a belt has been replaced recently or not as not only is access difficult, what you can see doesn’t give clear indication of its age.
Can I still drive with a worn cambelt?
Cambelts (also known as a timing belt) normally must be replaced according to manufacturer guidelines. Manufacturers give recommended replacement intervals, both in terms of age and mileage. It is preventative maintenance that should never be overlooked. If you suspect there is any issue with the cambelt or there are concerns about its age or condition, book a diagnostic inspection immediately and do not drive the vehicle. A snapped or broken timing belt can cause catastrophic damage to the engine.
If you have purchased a second hand vehicle and it has no timing belt change history, such as a garage invoice, then it is important to err on the side of caution and have it replaced as soon as possible.
How long does a Cambelt last?
How long a cambelt lasts will depend on a number of factors, generally this can range anywhere from 40,000 miles to 100,000 miles, or indeed a number of years. Manufacturers give recommended replacement intervals, both in terms of age and mileage. It is preventative maintenance that should never be overlooked. Intervals will depend on the vehicle's make and model.
Does changing the Cambelt improve performance?
A new timing belt won't improve engine performance, but can return engine to the correct state of operation and performance. As the belt loosens up and wears away over time, engine performance can reduce as the engine moves out of time to a small extent. Replacing the belt can help address that. Unfortunately in 99% of cases you will only know if there is an issue with the cambelt when it breaks.
Is a faulty cambelt an MOT failure?
No, a faulty cambelt should not lead to an MOT failure, the cambelt or timing belt is not checked as part of an MOT.
What can cause the timing belt or cambelt to break?
There are a few reasons why a timing belt or cambelt may break:
* Timing belt may be old and worn out.
* Timing belt may be damaged due to improper installation or tension.
* Water pump seizure can also cause the timing belt to break.
How much does it cost to replace the timing belt and the water pump together?
On average, the cost for a cambelt or timing belt replacement is £300. A water pump replacement generally costs between £115 and £375.
What does a bad or worn out timing belt sound like?
You may hear a clicking or ticking sound coming from the engine. You may also constantly hear knocking or slapping noises if the timing belt tensioner is unfastened and the timing belt is no longer tensioned correctly. In the worst case scenario you may find that you can't start your car at all if the cambelt has come off or has broken.
What is the difference between a timing belt and a timing chain?
A timing belt is made of rubber, whereas a timing belt is a metal chain. A timing belt is a toothed belt made of reinforced rubber that rides on sprocket wheels. As the belt turns, it spins the crank and cam shafts in sync so the valves open and close at the proper time. A timing chain is a metal chain that does the same thing as a timing belt.
The best thing to do is check your owner's manual as this will specify if your engine has a timing chain or belt.
Can low engine oil cause the cambelt to break?
In most cars, the tensioner is pressurised by the engine oil and in the absense of the oil pressure is lot leading to the belt getting loose or breaking completely. This can also occur when there is an engine oil leak.
Is the timing belt checked in the MOT test?
No, the timing belt is not checked during an MOT test which is why it's essential to get it replaced as per the manufacturer's recommendations. A worn out timing belt can snap and cause expensive damage to the engine.
How much does it cost to replace timing belt?
Cost for a cambelt or timing belt replacement is on average £300, with prices ranging from £200 to over £500. Ultimately, the cost of a timing belt replacement depends on your car and what parts your car's manufacturer recommends using for the replacement. Find out what you could save by having your timing belt replaced by ClickMechanic by selecting your car at the top of this page!
Check out the ClickMechanic price for a cambelt change. See the averages for different makes below. We consolidate industry standard data with millions of data points to give you the most accurate price.
| Name | Average Cost | |
|---|---|---|
| Audi | £554 | Get exact price |
| BMW | £1414 | Get exact price |
| Citroen | £447 | Get exact price |
| Ford | £472 | Get exact price |
| Land Rover | £502 | Get exact price |
| Mercedes-Benz | £639 | Get exact price |
| Nissan | £534 | Get exact price |
| Peugeot | £457 | Get exact price |
| Renault | £662 | Get exact price |
| Toyota | £616 | Get exact price |
| Vauxhall | £395 | Get exact price |
| Volkswagen | £467 | Get exact price |
Estimates on average repair costs, such as the above results for a cambelt change, are based on ClickMechanic's quote data which combines multiple third-party sources. Actual costs may vary. We provide estimates on average repair costs for information only and accept no liability for any inaccuracies or errors. If you think an estimate is incorrect, please contact us to let us know.
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Mechanics that undertake cambelt work
- Absolute Alloys, Edenbridge
- Aj Motors, Southampton
- Amdb Autotek Uk, Birmingham
- Breckland Mobile Mechanics, Thetford, Norfolk
- Bridgeway Garage Nottingham Limited, Nottingham
- Campbell's Mobile Mechanics, Rainham
- Chelmsford Prestige, Chelmsford
- Gp Mot & Service Centre Ltd, Westbury Wiltshire
- J.A.M Service, Spilsby