A beginner’s guide to car maintenance jargon
Whether it's a warning light on your dashboard or a mechanic's technical talk that's leaving you scratching your head, we've put together this jargon buster to help you know exactly what all those car terms mean.
Having a basic understanding of vehicle safety and maintenance is never a bad thing - it can help keep you safe - and save you money.
Not knowing what common jargon means can leave you at a disadvantage when dealing with mechanics and car dealers when you’re shopping for a car, or simply taking your motor in for its service or MOT.
So, here's our glossary covering some of the most common motoring upkeep and performance terms.
We asked the experts at Kwik Fit to assess how serious, or not, replacing some of the parts listed below might be.
However, it's notoriously difficult to estimate the average cost of garage work because factors like the make and model of your car, your location and the price of labour per hour have to be considered, but we've had a go in a few instances.
A filter that catches dirt, dust and debris which could damage your engine or reduce performance. Air filters should be replaced in line with the service schedule recommended by the manufacturer. A new air filter can cost as little as £10.
ABS (anti-lock braking system)
This is designed to help the driver maintain control of the vehicle under heavy braking by stopping the wheels from locking or sliding, which can retain steering control in an emergency. An ABS system rapidly applies, releases and re-applies the brakes to slow you down without locking the wheels.
Autonomous Emergency Braking is a safety system which scans the road ahead and can apply the brakes automatically to avoid a collision at low speeds, or reduce an impact at higher speeds.
AWD (all-wheel drive)
This means the engine is powering all four wheels, and is otherwise known as ‘4x4’. These cars tend to provide better grip, which is why many off-roaders and performance-orientated cars have this.
This converts mechanical energy from the engine into an alternating electrical current, which is stored in the battery and powers the vehicle’s electrical systems. It’s the alternator’s job to keep your battery topped up, so if it’s working correctly you should never have a flat battery - unless you leave the lights on all night. (If you have a hybrid or electric vehicle you probably won’t have an alternator)
Typical cost (replacing an alternator): £295
Job difficulty: 6/10
Kwik Fit comment: "Modern alternators provide significant power from the rotation of the engine, via the drive belt. Some systems feature smart control systems or clutch pullies which are designed to improve the fuel efficiency of the vehicle by only generating power when the engine load is reduced."
Automatic transmission fluid
If you drive an automatic car, make sure the transmission fluid level is always topped up. This fluid cools the transmission system and lubricates moving parts.
This is phrase used to describe when a large bearing in the engine has worn out and failed. You'll know if this is the case because there's likely to be a loud knocking noise from under the bonnet, especially when you accelerate. It’s serious, but might not be ‘game over’ for your car because it may be possible to fit a replacement engine. Either way, it’s going to be expensive.
A metal disc coupled to the wheel which is clamped between two brake pads in a braking system. As the brake disc slows down due to friction, so does the car’s wheel.
Typical cost (replacing brake discs on both front wheels): £145
Job difficulty: 5/10
Kwik Fit comment: "Brake discs are replaced in pairs to ensure vehicle stability is maintained under braking. Brake pads should be replaced at the same time to ensure that any contaminates or uneven wear on the old pads aren’t transferred to the new discs."
A steel plate with a pad of hard-wearing friction material bonded to one side. When the brakes are applied the hydraulic pistons in the brake calliper push the brake pads against the brake disc.
Typical cost (replacing brake pads on both front wheels): £90
Job difficulty: 4/10
Kwik Fit comment: "Brake pads generally require replacement when the friction material wears down to a pre-set level, although they can be affected by external contamination from leaking brake fluid or oil."
These are small 'cushions' made of rubber which are attached to suspension parts. They work like knees or elbows in the human body, absorbing bumps in the road and prevent metal-to-metal contact. Because they are rubber, they can perish and wear out, so do need to be replaced now and again. They are not expensive, though replacement time will depend on the make and model of car you drive.
This rubber belt drives key moving parts of your engine, including the camshafts, ensuring everything is running at the right speed. For this reason, it’s sometimes known as the cam belt. An old or well-worn timing belt can snap and instantly cause massive amounts of damage to your engine, so it’s important that it’s changed in line with the manufacturer’s recommendations. Some cars have a chain instead of a belt, and they're designed to last the car's lifetime so generally won’t need replacing unless there's a serious problem.
Typical cost (replacing a timing belt): £240
Job difficulty: 9/10
Kwik Fit comment: "The timing belt is a critical piece of the engine which normally requires significant dismantling and special tools to replace. When the timing belt is replaced it often makes sense to replace ancillary items like a water pump at the same time as labour costs will be reduced.”
These are fitted to petrol cars and convert poisonous exhaust emissions into carbon dioxide, oxygen, nitrogen and water. They should last the lifetime of the car, but can fail in some circumstances, usually because of a fault somewhere else on the car causing a domino effect of failures. They are expensive items and there have also been instances of catalytic converter theft.
Typical cost (replacing a catalytic converter): £325
Job difficulty: 7/10
Kwik Fit comment: “It is important to resolve the cause of the failure before replacing the catalytic converter. Sensors that monitor the catalyst should also be replaced to ensure proper operation of the new catalyst."
The clutch connects your engine to your gearbox. In a manual car, when you press the clutch pedal, the clutch disconnects the engine from the gearbox temporarily so you can change from one gear to another. The clutch will eventually wear out with use, so will need replacing.
Typical cost (replacing a clutch): £340
Job difficulty: 9/10
Kwik Fit comment: "Replacement of the clutch requires removal of the gearbox so it can be a labour-intensive job. Modern clutch systems can require specialist tools to properly align and set up."
Also known as antifreeze or anti-freeze, this fluid helps to keeps the engine operating at the right temperature, so it's essential to keep the reservoir topped up. It also prevents scale building up and protects against corrosion in the cooling system. Like engine oil there are many varieties, and it is important to use the correct one for the vehicle to prevent engine damage.
This fan pulls air into the vehicle’s radiator, helping to cool the coolant, or antifreeze fluid, inside the cooling system and maintain the engine at the correct operating temperature.
Carbon dioxide is the gas emitted from the exhaust of a car as a result of an engine burning fuel. It's measured in g/km. Known as a greenhouse gas, carbon dioxide emissions are the primary driver of global climate change.
Dubbed the backbone of the internal combustion engine, the crankshaft is responsible for the proper operation of the engine and converting the up-and-down motion of the pistons and connecting rods into rotary motion.
Another vital part of an engine, a cylinder is a tube or chamber where fuel is combusted and power is generated. Inside the cylinder there is a piston which is forced down during combustion, generating power to move your vehicle.
A component that sits on top of the cylinder block, closing it to create the combustion chambers. It is important that there is good sealing between it and the block. The cylinder head contains the valves that let air, fuel and exhaust flow in and out of the cylinder.
A continuously variable transmission (CVT) is a type of automatic gearbox, often used in hybrid cars.
Also known as shock absorbers, dampers are a mechanical or hydraulic device designed to absorb bumps, or 'shocks', in the road. Dampers help to deliver a smoother and more comfortable ride.
Diesel particulate filter (DPF)
A device that removes small particles from the exhaust emissions of diesel engines. Cars fitted with one are designed to burn this soot and turn it to ash by running at high speeds for an extended period: above 40mph for 10 minutes or more. If you only make short journeys in stop/start traffic, and never make the longer, high-speed journeys the car needs, the filter can become blocked and fail.
Performed by a vehicle technician or mechanic, this is to check for vehicle sensor faults. A specialised code reader is plugged into the car’s Electronic Control Units (ECU) to detect problems with your vehicle which may be difficult to spot manually.
A mechanical device that allows the driven wheels of a car to turn at different speeds, splitting engine power between the wheels so that the outside wheel in a corner can rotate faster than the inside wheel.
Drive (or Auxiliary) belt
Historically referred to as a fan belt, this strong rubber belt drives multiple mechanical parts at once which can include power steering pumps, alternator, water pumps and air conditioning.
A vital form of lubricating oil that reduces wear and tear on moving parts of your engine. There are different oils for different engines, so make sure you use the right one.
Most modern vehicles have at least one on-board computer known as an Electronic Control Unit - a device which controls all the electronic features in a car. If a warning light appears or another fault develops on your car, a vehicle technician can plug in to the ECU to access any fault codes that may have been generated.
Electronic stability control is a safety feature which uses a collection of sensors to help detect and counter any loss of grip or traction which could cause the vehicle to over or under steer.
A car's exhaust system controls noise, directs fumes away from the driver and passengers, reduce the air pollution your car produces and improves the performance of the engine. There are several parts to the exhaust system, including the manifold, catalytic converter, sensors, silencer and exhaust pipe and every part must be function properly for it work perfectly.
A replaceable metal or plastic filter which prevents particles and contaminants in the fuel tank from reaching the fuel pumps or injectors and blocking them. It is critical that these are replaced at the correct intervals to avoid costly damage to the fuel system.
A small pump which sends the fuel from the tank to the engine. Vehicles with direct injection fuel systems can have multiple pumps to generate the very high pressures used in those systems.
FWD (front-wheel drive)
This means the engine is powering the front wheels, essentially dragging the car along the road. Most cars are front-wheel driven, although some sports and performance cars use the rear wheels because FWD cars have less front-end grip during high-speed cornering. In everyday driving, you won’t notice a difference.
This electrical heating device helps diesel engines start from cold. They help achieve the correct temperature by warming the air in the combustion chamber. Each cylinder usually has its own glow plug. On modern diesels they are also used to maintain emission standards.
A leak-proof seal between an engine’s cylinder block and cylinder head. It keeps the various fluids and gases in the correct chambers of the engine.
Horsepower refers to the power an engine produces. HP is similar to BHP, PS and kW.
Partially electrified vehicles. In other words, they combine a battery with an internal combustion engine. They are a compromise between 100% electric cars with limited range and traditional petrol and diesel-powered vehicles. Broadly speaking, there are three types of hybrid: mild hybrids, self-charging (or full) hybrids and plug-in hybrids.
A hydrogen fuel cell electric vehicle (FCEV) is much like an electric car except that it derives energy from a fuel cell which converts compressed hydrogen into electricity. Many hydrogen cars also feature lithium-ion batteries, which store the electricity that has been produced.
An electrical component used to transform the battery's voltage to the thousands of volts needed to create an electric spark in the spark plugs to ignite the air/fuel mixture in internal combustion engines.
A car immobiliser is an electronic security device that stops your car from being started or taken without its key - so it makes life pretty difficult for would-be thieves. You can check your car's handbook to see if it has a factory-fitted immobiliser as standard.
Also known as a V5C document, it indicates that a person is the registered keeper of a vehicle — not the owner. The car could be owned by a third party such as a finance company or fleet operator. The person named on the V5C is legally responsible for the vehicle. As such they’ll have to deal with things like parking tickets, speeding and contact with the police if a motoring law is broken. When you buy or sell a car, there are parts of the V5C for both the vendor and buyer to complete. If you’re buying a car from someone and they can’t show you the logbook, walk away. The car may not legally be theirs to sell.
A cylinder containing a piston and hydraulic fluid, directly linked to a foot pedal and used to generate the pressure to operate the brake or clutch.
A test which, by law, must be carried out each year on all road vehicles in the UK that are more than three years old. It is a test of vehicle safety, roadworthiness and exhaust emissions. Kwik-Fit offers a free reminder service to make sure you don’t forget when your MOT is due.
OEM (Original Equipment Manufacturer)
A term used to categorise parts assembled and installed during the construction of a vehicle.
A small filter fitted to an engine’s lubricating system, used to remove dirt and particles from the engine oil.
A pump used to circulate engine oil under pressure to the engine, lubricating moving parts.
Oversteer (also see Understeer)
Sometimes occurring on real-wheel drive cars, it's when a driver applies more power than the tyres can deal with. This makes the tyres slip as they try to push in the opposite direction to the turn, kicking the back end of the car out. Needless to say, 'losing the back end' of a car like this is dangerous, so drivers of RWD cars should be especially cautious in slippery conditions.
PHEV (plug-in hybrid electric vehicle)
A type of hybrid car which can be plugged in (usually overnight) to charge up the on-board battery which generally delivers up to 30 miles of pure electric motoring.
Steering that is aided by electric or hydraulic motors, reducing the effort required by the driver to steer the car, particularly at low speed. Drive a classic car without power steering and you realise it's a more physical experience.
The radiator prevents your car from overheating. It’s full of fluid - normally antifreeze - which runs through the engine, absorbing the heat the engine produces. It then comes back to the radiator, at the front of the car, and is cooled by the air rushing over it, and a fan.
A term used by electric vehicle drivers when they fear they will not have enough charge to reach their destination.
In hybrid and electric cars, this system adds charge to the battery by harvesting energy otherwise wasted during braking and coasting. This in turn reduces wear on the friction brakes.
RWD (rear-wheel drive)
This means the engine is powering the rear wheels, pushing the car along the road and leaving the front wheels to steer. Rear-wheel drive cars are often more enjoyable to drive at high speeds, but have less grip in slippery or snowy conditions.
Also known as dampers, a shock absorber is a mechanical or hydraulic device designed to absorb bumps, or 'shocks', in the road. Shock absorbers help to deliver a smoother and more comfortable ride.
Typical cost (replacing a pair of front shock absorbers): £220
Job difficulty: 6/10
Kwik Fit comment: "Damper units play an important part in vehicle stability, dampers in poor condition don’t remove spring movement effectively and can cause bounce. Damper replacement should be considered at higher mileages and when broken springs are replaced."
These create the spark that ignites the mixture of fuel and air in your engine. If the spark plugs aren’t working, the car won’t start when you turn the ignition.
As its name suggests, this small electrical motor is used to start the engine. It uses power from the battery to turn the crankshaft via the flywheel to start the engine.
Connecting the two front wheels, the system moves left and right to turn the wheels.
Torque is a measure of the amount of pulling power an engine generates and is usually expressed in (lb ft) newton metres (Nm). Electric vehicles (EVs) have instant torque and can accelerate from standstill as fast as supercars back in the day.
A system which monitors and regulates the speed at which the wheels are spinning, helping to keep all four wheels of the car gripped firmly to the road.
Also known as front wheel alignment, tracking generally refers to the toe angle of the front wheels and is one of several geometry angles checked during full wheel alignment.
Another name for a car’s gearbox, this component turns the engine’s power into a way of propelling a car's wheels. Cars either have a manual or automatic gearbox.
A performance device that uses a turbine driven by the engine exhaust gases to drive a compressor which forces air into the engine. This increases the air/fuel mixture flow into the engine and increases the engine’s power.
Understeer (also see Oversteer)
This is when the car’s front wheels lose grip through a corner due to excessive speed, causing the front end to push towards the outside of the corner. Instead of turning, the car is likely to plough straight on. It generally happens when you're going too fast, braking very hard or in slippery conditions.
This is used to circulate coolant, or antifreeze, through the cooling system. It's connected to the radiator and the engine by a series of hoses.
Also known as tracking, wheel alignment is the process of adjusting components to a specified camber, toe, caster and ride height to balance the suspension and improve tyre wear. Misaligned wheel alignment can cause uneven and rapid tyre wear, worn suspension units and poor fuel economy. Front wheel alignment costs from around £59. Incorrect wheel alignment can also affect the operation of vehicle Advanced Driver Assistance Systems (ADAS).
Correctly balanced wheels provide a smooth ride. Wheel balancing, which should be carried out when you are having a new tyre fitted or the tyre is removed for a puncture repair, involves adding weights to the wheel rims to ensure the weight is distributed evenly across the wheels and they spin smoothly without vibrations. The cost of wheel balancing is generally included when you have a new tyre fitted.