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Find out what a cam belt is and when to replace it
The cam belt, or timing belt, is an essential component of your car’s engine. But what does it do, when does it need replacing and what happens if it breaks?
What is a cam belt?
A cam belt is made of rubber and is an important part of an internal combustion engine in a vehicle – it works to synchronise the rotation of the crankshaft and camshaft and makes sure that the engine’s valves open and close at the right time during each cylinder’s intake and exhaust strokes.
Cam belts have teeth on the inside that match up with the corresponding teeth on the crankshaft and camshaft gears. Cam belts need to be replaced at certain intervals to prevent them from breaking and causing serious damage to the engine.
What is a timing belt?
A timing belt is just another name for a cam belt, both refer to the same thing – a toothed belt that is part of the internal combustion engine in a vehicle.
What does a cam belt do?
The main role of a cam belt or timing belt is to control the timing of your vehicle’s internal combustion engines. It controls the timing and sequence of when the valves to the cylinders open and close. To do that, it makes sure that the crankshaft and the camshaft rotate in sync.
- The engine’s camshaft controls the valves, letting a mixture of fuel and air in and exhaust gases out
- The crankshaft moves the pistons up and down at the same time
- These two actions must be synchronised
- If the timing's off, the valves, pistons or other engine parts could get damaged
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When to replace your cam belt
There’s no set rule for when to replace your cam belt. It depends on the make and model of your car, as well as how much you drive the car. It’ll usually need to be replaced more than once over the course of a vehicle’s lifetime.
Manufacturers will usually recommend replacing your timing belt after a set number of years or miles. This could be anywhere from 40,000 to 100,000 miles or 4+ years.
Check your vehicle handbook to see what your manufacturer recommends.
How do I know if my cambelt needs changing?
Your cam belt might need replacing sooner than your vehicle manufacturer’s schedule recommends. There are a few tell-tale symptoms to look out for and things that can go wrong:
Noises from the engine
You should check out any unusual noises from the engine straight away. Cam belts don’t usually give much notice before they fail, but a rubbing sound from the belt cover area is a sign it’s about to fail. If you hear it, switch the engine off and call a mechanic to check it.
Engine misfires
If your cam belt sustains damage, it can result in poor engine performance or misfires – caused by incorrect timing of the engine’s valves.
Visible damage
If you’re able to remove your engine cover, then you’ll be able to visually inspect your cam belt for any damage. You’ll want to look out for any fraying, cracks or missing ridges (or ‘teeth’).
Car won’t start
If yourcar won’t start, it could mean there’s a problem with the cam belt. If the cam belt is broken, then the cam shaft won’t rotate when the crankshaft turns, so the car may not start at all.
If you can’t start your car,call us out to help with your breakdown.
How much is a cam belt change?
The price of a new cam belt or timing belt plus labour varies depending on the make and model of your vehicle. Prices for parts and labour can start from around £250 and go up to over £500, or even over £1,000 for some luxury vehicles.
When you get a quote, make sure it includes the price of the belt, tensioners and labour. In some cars, you must take the timing belt off to get to the water pump. So, if you need to change the cam belt, some people choose to have the water pump changed at the same time as the cam belt will already be off.
Can I replace a timing belt myself?
We don’t recommend that you try to replace a cam belt (timing belt) if you have little experience. Even if you consider yourself a DIY mechanic, a cam belt replacement is a complex job that requires several hours of work and specialist tools.
A replacement involves removing engine parts like the cam belt cover, water pump, and tensioner, and getting the engine’s valves to be perfectly synchronised requires precision timing. If you need a replacement, make sure to take your car to a professional mechanic.
How can I tell if a car has had its cam belt changed?
If you’ve acquired a new car and you’re wondering if the cam belt was recently replaced, you can always check the maintenance records (if these have been provided with the car). The maintenance records should also indicate the date of the replacement and how many miles the car has done since it’s been fitted.
You can also ask the former owner or the dealership where you bought the car, and check for stickers or markers on the engine or maintenance records for evidence of recent work.
How long do cam belts really last?
This depends on the make and model of the vehicle – so make sure to check your vehicle handbook for the recommended intervals for changing a cam belt. Generally, it’s recommended to get your cam belt checked every 40,000-100,000 miles or 4 years, whichever comes first.
What are the consequences of a cam belt not being changed at the recommended time?
If you don’t get your cam belt changed at the correct time, you run the risk of damaging your vehicle in or losing money in the following ways:
- Engine damage – if the cam belt is damaged, the pistons in your engine can collide with the valves, and break or bend them
- Poor engine performance – you’ll likely notice reduced power or acceleration due to the cam belt being worn or stretched. These symptoms are likely a precursor to the cam belt breaking or your engine sustaining major damage, so make sure to get it checked by a mechanic as soon as possible
- Bad fuel economy – if your cam belt is causing your engine to have reduced performance, then it’s very likely that your fuel won’t last as long, and you’ll have higher emissions
- Expensive repairs – worn or broken cam belts can cause extensive engine damage, sometimes to the point where the better option is to replace the entire engine, which could set you back quite significantly
Is it safe to go a little bit over the cam belt interval?
No. The cam belt is a vital part of your vehicle’s engine, and failing to keep up with the proper checks and replacements for it could result in major damage to your vehicle. If you’re getting near to your next recommended cam belt replacement date, make sure to take your vehicle to a professional mechanic – they’ll be able to advise on when you should get it changed.
Reasons for cam belt failure
One of the main reasons for cam belt failure is the auxiliary belt. If the aux belt deteriorates and shreds, the fibres get trapped under the cam belt as they both run off the crank shaft pulley. This usually causes the belt to jump or come off altogether.
On many cars, the cam belt also drives the water pump, so any issues with that can cause a failure too.
What happens if the cam belt breaks?
It’s always better to get your cam belt checked with regularcar servicingor to take it to a garage as soon as you notice a problem. If you leave it and the cam belt snaps completely, it’ll cause a much bigger problem.
- If the cam belt snaps while you’re driving, it could be very dangerous – the engine could seize up, causing steering and brakes to fail
- The pistons can hit the valves in the cylinders, damaging the engine
- A non-interference or free-wheeling engine won’t suffer as much damage, but still might sustain some
It’ll be much more expensive to fix if the timing belt snaps and causes other engine damage.So if you notice any unusual noises or a drop in engine performance when you’re driving,pull over in a safe place and tell us.
Engine problems? Get peace of mind if you break down.
Cam belts vs cam chains
The main difference between a cam or timing belt and a timing chain is the material. Unlike cam belts, timing chains are made of metal.
Timing chains are housed inside the engine and are lubricated by theengine oil, while cam belts are usually located outside the engine. But some manufacturers are now using “wet belts”, which like cam chains, run internally in the engine oil.
Cam chains tend to last longer as they’re made of a stronger material. Unless they’re “wet belts”, cam belts can dry out and crack over time if they’re not replaced.
If your vehicle does have a wet belt, it’s important to top up with the correct grade of oil. The wrong type of oil can degrade the wet belt prematurely, causing it to fail.
Does your car have a cam belt or a chain?
Whether your car has a timing belt or a timing chain depends on the make and model. For example, most BMW and Mercedes cars use cam chain engines.
Check your vehicle handbook to find out whether your car has a belt or a chain.
Cam belt wear and tear
The cam belt can wear out over the course of a car’s lifetime. On many cars, it can be tricky to get to the cam belt, so we always recommend taking your car to a mechanic if you’re not sure. Stick to your manufacturer’s servicing schedule for the best chance of spotting any problems.
Last updated:18 July 2024 | Author: The AA
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