• Your cambelt needs changing

  The cambelt (or timing belt) – essentially a large, strong rubber-toothed belt that connects major moving parts of your engine – needs replacing. Cam belts need replacing over time. If you don’t replace your cam belt at the recommended intervals, it can cause significant damage to your engine.
  What should you be aware of?
  All manufacturers recommend that you change the cambelt after either a certain number of miles or a certain number of years. Check your owner’s manual to see when yours is due. This is an essential job that must be done. If you’re advised that the belt needs changing before this time, ask the technician to explain why.

• Your big end has gone

  A large bearing (semi-circular sleeve of metal inside the engine) has worn out and failed. This usually results in further damage to other parts of the engine. If the big end is worn it can make a loud knocking noise, especially when you accelerate.
  What should you be aware of?
  Big ends are tough and rarely wear out. Because of this, any problem that has led to this diagnosis could actually be caused by a simpler problem. Ask the garage to explain their diagnosis as this problem is very rare in modern cars.

• Your little end has gone

  A small bearing that fits in the connecting rod attached to the piston has worn out. You will hear a light knocking noise from the engine.
  What should you be aware of?
  Like the big end, the little end is rarely the cause of any problems, so ask your garage to explain their diagnosis.

• The clutch is slipping

  Part of the clutch mechanism which allows you to change gear smoothly is so worn it is not working properly. When you select a gear, your car will still feel like it’s in neutral or, when you accelerate, the engine revs but the car doesn’t go any faster.
  What should you be aware of?
  Clutches are rarely repaired so you’ll probably need a new one. Some technicians may suggest the gearbox also needs to be repaired or replaced at the same time. This is unlikely so always question this suggestion rather than letting the technician do it as a matter of course. If the clutch has been slipping for some time, the flywheel (a mechanical device that helps drive the engine) may also need to be replaced or skimmed (similar to the way a carpenter planes wood to produce a smooth surface). Remember, if in doubt, ask for an explanation.

• Your sump is dripping

  The sump is the oil pan that sits at the bottom of the engine, nearest the ground. Sometimes the seal on the plug that allows oil changes to be done can fail, causing a leak.
  What should you be aware of?
  Leaking oil is hardly ever a major problem – usually a small part called the drain plug washer simply needs replacing. In some cases the sump gasket (the seal between the sump and the engine) may also have failed so have the causes investigated, but never ignore an oil leak as an engine with too little oil can quickly become damaged.

• Your engine is misfiring

  Your engine isn’t running as it should be. It may jerk when accelerating and can often cut out when pulling away.
  What should you be aware of?
  Engines can misfire for a number of reasons so the garage will need to investigate the causes. It could be something as simple as worn spark plugs, or faulty sensors – devices that measure your engine – may be to blame.

• Your fan belt is screaming

  Either the belt that drives the alternator (see electronic systems below) or the fan which cools the radiator is slipping, causing friction and making a high-pitched noise when you press the accelerator or when weather conditions are damp.
  What should you be aware of?
  Most of the time it’s best to simply fit a new fan belt. However, sometimes they may simply need adjusting, so it’s worth asking as it could save you money.

• Your head gasket’s gone

  The seal between the main engine casing (known as the cylinder block) and the cylinder head (a cast iron or aluminium cover at the top of an engine) has cracked as a result of wear and tear, leading to internal engine leaks.
  What should you be aware of?
  If your car is modern, the cause of the problem is unlikely to be with the head gasket. Ask your technician if he or she is sure there isn’t anything else that may be responsible for the problem.

• We need to do a pressure test

  Pressurised liquid needs to be pumped through the cylinder head to check for cracks or leaks. This is because small cracks caused by overheating are not always easy to see.
  What should you be aware of?
  This method is often used to identify any problems before refitting the cylinder head. It’s a specialist job, often contracted to a specialist engineering organisation to do.

• Your cylinder head needs skimming

  The cylinder head (see above under ?Your head gasket’s gone) has overheated and may be distorted and is no longer sealing correctly. It is sometimes possible to grind the surface down by machine so that it fits into place correctly.
  What should you be aware of?
  This can be a cheaper alternative to replacing the cylinder head. Again, this is a specialist job and is often contracted to a specialist engineering organisation.

• You have ‘mayonnaise’ (or ‘sludge’) under your oil filter cap

  There’s a thick, white substance under the oil filler cap that may indicate a problem with the head gasket. The sludge is caused by water or condensation mixing with engine oil.
  What should you be aware of?
  It’s likely your head gasket will need replacing; ask your technician if he or she is sure that there isn’t anything else that may be responsible for the problem.

Steering, suspension and brakes

• Your brake pads are worn

  Brake pads are small metal-backed plates with a friction material on the surface. They push against a metal brake disc when you press the brake pedal (see below) to slow or stop the vehicle. With use they begin to wear out.
  What should you be aware of?
  Worn brake pads will need to be replaced or the brakes will not work effectively. It can also mean that other parts (like the discs) may become damaged. Their life span depends on a number of factors including your driving style (if you brake a lot or brake heavily) and weather conditions. Always replace the pads with those recommended by your manufacturer.

• Your brake discs need replacing

  The brake discs are metal discs the brake pads push against when you press the brake pedal.
  What should you be aware of?
  While braking systems are designed so that the pads wear first, the discs can also wear down and need replacing from time to time. Discs can be damaged if pads are allowed to completely wear out, so it’s a false economy to skimp on replacing them when they are worn.

• Your ABS isn’t working

  There’s an issue with your anti-lock braking system. This is the safety system that helps to prevent the wheels from locking up when you are braking.
  What should you be aware of?
  Modern antilock brakes are far more reliable and less likely to need repairing than the older systems. Problems are often caused by dirt or rust getting into the sensors, which activates the ABS light and shuts down the system. This means that repairs can be simple if the garage investigates the problem correctly.

• Your dampers are worn

  One or more of the dampers – more commonly known as shock absorbers – need replacing.
  What should you be aware of?
  Dampers are a part of your car which suffer a tremendous amount of wear and tear. Because of this they can need replacing from time to time. Worn dampers can be dangerous – they prevent your tyres from connecting with the road surface properly. This increases your stopping distances and significantly affects your car’s ability to hold the road (in other words you are more likely to skid). Not replacing them can be a false economy. If your dampers are very worn, they can cause complicated parts of the suspension and steering to become damaged.

• Your wheel cylinder is leaking

  The wheel cylinder – a part of the braking system that puts force on the brake drum to slow and stop the vehicle – is leaking hydraulic fluid.
  What should you be aware of?
  Leaking cylinders will affect the performance of the brakes and should be investigated as soon as possible.

• You have a hydraulic leak

  Your vehicle is losing hydraulic fluid, normally from the power steering system, which could be extremely dangerous. If the system drains of fluid completely, it will stop working and the steering will become stiff.
  What should you be aware of?
  Like the human body, most car problems have physical symptoms. Ask the technician to show you the problem on the vehicle so you are comfortable in knowing what work is needed.

• Your brakes are ‘spongy’

  Your brakes aren’t operating properly. It doesn’t feel like there is much resistance when you press the brake pedal – usually because of a loss of brake fluid.
  What should you be aware of?
  The leak must be identified, fixed and the faulty part replaced. The brake fluid may need changing. Many manufacturers recommend replacing the fluid every two years. Check your owner’s manual for specific recommendations.

• The bushes on the wishbone are going

  The bushes (rubber parts) on the wishbone (part of the suspension system) have either worn out or are wearing out.
  What should you be aware of?
  As they are rubber, bushes can crack and perish and need replacing. Worn bushes can lead to a lot of noise from the suspension and steering as well as affect how the suspension and steering work.

• Your wheels need balancing

  The car’s wheels are unbalanced. This can cause the steering wheel to vibrate when you are driving at speed.
  What should you be aware of?
  Most wheels and tyres have slight imperfections, which cause a vibration at certain speeds. These imperfections are countered by using small lead weights fixed to the wheels – a simple and quick task for a competent technician with the right equipment.

• Your tracking is out

  Tracking refers to the front wheels being in line, as shown in the manufacturer’s specifications.
  What should you be aware of?
  Damaged or incorrectly adjusted tracking can affect how your car handles. This can cause it to pull to one side. It can also lead to your tyres wearing out before they should or unevenly. Your tracking can easily be affected by hitting kerbs or potholes. It is always a good idea to have your tracking checked when you have a service or when replacing the front tyres.

• Your tyres are illegal

  One or more of your tyres doesn’t have enough tread – the ridges in the tyre’s surface that allow it to grip the road – or are damaged.
  What should you be aware of?
  You should replace the tyres if they become damaged or when the tread reduces to 3 millimetres. By law they must be replaced when the tread reduces to 1.6mm. If in doubt, ask your garage to check their condition.

• We need to run a diagnostics check

  The garage needs to connect your car’s engine management system to a computer which can read the information, so they can identify the source of any problems.
  What should you be aware of?
  Modern cars have incredibly complicated electronics systems that manage a variety of different aspects of the car’s performance and function. Not all garages have the equipment – known as ?diagnostics’ – needed to read the information on the engine management system. This is because it is very expensive equipment for a garage to buy and maintain. Always check they have the kit needed for your particular make and model of car.

• We need to access the ‘CAN-bus’

  This is jargon for the electronic system that allows the vehicle’s engine management computer to ?talk’ to different parts of the car.
  What should you be aware of?
  If a technician is using diagnostics software, they can have access to the ?CAN-bus’ so they can identify and fix specific problems. If a technician hasn’t got the right equipment or is dishonest, they will not use this information and simply change parts until the problem is fixed – an expensive process for you!

• The EML is on

  ‘EML’ is jargon for engine management light, otherwise known as ‘MIL’. This is a warning light that appears on the dashboard to let you know about a major problem with the engine or systems.
  What should you be aware of?
  The engine management light can come on for a number of reasons so you need to take your car to a garage with the diagnostics equipment which can connect to the engine management system. Only a garage with these tools can diagnose the problem and reset the light.

• Your alternator needs replacing

  The part that constantly recharges the battery while you are driving is faulty, meaning the electrics on the car have stopped working, or will soon do so.
  What should you be aware of?
  Alternators can be placed under stress by an old or partially charged battery, and failure is a common fault in cold weather. You should always ask the technician to check the battery is healthy as this could be the cause of any problems rather than the alternator itself.

• Your service light is on

  Many modern cars tell you when a service is due by lighting up a warning light on the dashboard.
  What should you be aware of?
  Never ignore this light! Regular servicing increases the efficiency of your car and means it will last longer. Keeping to a servicing schedule is usually a condition of any warranty.

Exhaust system

• The catalytic converter is clogged or worn out

  The device used to reduce the harmful nature of engine emissions in the exhaust system is not working correctly.
  What should you be aware of?
  Also known as the ‘cat’, the catalytic converter can become worn or blocked over time. A problem here can also show that there is a fault elsewhere in the engine so you should not ignore it. Catalytic converters may seem expensive but they are essential to your car running efficiently and reducing the amount of fuel you use.

• The exhaust is blowing

  There is either a hole or crack in your exhaust system, preventing it from working properly and leading to it making a louder noise than normal.
  What should you be aware of?
  Over a period of time the exhaust system will need to be replaced. However, sometimes it may just be a part that needs replacing. Always ask to see the hole or crack and for an honest opinion on the best action to take.

• Your car failed its emissions test

  The emissions test is part of the MOT test. A failure means that your car is releasing too many pollutants.
  What should you be aware of?
  The emissions test is a good indicator of other problems within the engine and exhaust system. Poor emissions are a sign that the engine is not running efficiently and is burning more fuel than it needs to. Normally a service will identify any issues which may need attention.

Air Conditioning

• You have a clogged pollen filter

  The air-conditioning filter needs replacing as it is either full of bits (often dust and leaves), or just simply blocked.
  What should you be aware of?
  A clogged filter will not only prevent clean, cold air reaching the inside of the car, but can actually stop the air-conditioning system from working altogether. If you suffer from hay fever or allergies, you should pay particular attention to your air-conditioning filters as a clean filter will dramatically reduce the amount of pollen which gets into the car.

• You need a re-gas

  Air-conditioning systems contain a pressurised refrigerant gas that cools the air as it enters the cabin. The system naturally loses pressure over time, or can spring a leak.
  What should you be aware of?
  Low pressure in the air-conditioning system means it won’t be working efficiently. Re-gassing is a simple and low-cost procedure that should be done every year or two as part of an air-conditioning service. Get the technician to also check that the seals are in good condition. They can do this by using a dye in the system to check for leaks.

• Your air con needs cleaning

  Bacteria can build up within an air-conditioning system, leading to an unpleasant smell.
  What should you be aware of?
  A good-air conditioning service will include a process that removes extra moisture from the parts and gets rid of any bacteria.

Other general terms

• Your car passed its MOT, but here’s the advisory sheet

  If your car passes its MOT, the garage may give you an advisory, or ?amber’, sheet. This will point out items that may be worn and will need attention in the near future to prevent bigger problems or, perhaps, your car failing its MOT in the future.
  What should you be aware of?
  You should keep an eye on any issues identified in an advisory or amber sheet and ask for them to be included in any service schedule. If your car is not due for a service, ask the technician when the items should be checked again. Do not leave them until the next MOT.

• You need a service

  Your car is due, or is overdue, a minor or major service. You need both services at different stages of a car’s life. See your owner’s manual for details of what’s right for your car.

  A minor service generally refers to oil and filter change and a visual check of the major parts. A full or a major service includes a much more thorough check of the car. Parts which wear out with use are replaced during this service.
  What should you be aware of?
  A regularly serviced car will be more efficient, less prone to breakdowns and will last longer. Servicing within certain mileages or years is also a typical condition of a warranty.