Mechanics' terminology: Carbuyer's jargon buster

It's something many of us are familiar with; your car is in the garage for whatever reason – be it a barely audible noise coming from somewhere or because it’s expired in a cloud of smoke and steam at the side of the road – and the technician takes it away to have a look.

They come back, or call you up, and start to explain what’s gone wrong, what can be done to fix it and how much it’ll cost.

It’s at this point that you may start to get a little lost – but don’t forget that most mechanics are highly-trained individuals, not stereotypical ‘grease monkeys’ and have to deal with very complex mechanical, electrical and plumbing issues every day, so they’re used to talking in a certain way.

Here, we’ll try to demystify some of the most common terms you. But if you think we’ve missed anything out, do get in touch in the comments below.

“You need new pads and discs”

This refers to your car’s brake pads and brake discs – two of the main parts of the braking system. Because they’re almost constantly in use, they wear out after a certain period of time. Getting them fixed and/or replaced is part and parcel of car ownership.

There are a couple of particularly common brake issues and mechanics often suggest changing pads and discs at service time. Essentially, the disc is the part of the braking system that spins with the wheel, while the pads grip that disc to slow the car down when you press the brake pedal. Due to friction between the two, they both eventually wear down.

But how do you know whether you really need new ones or if your mechanic is just being overly cautious? Well, if your pads or discs are getting worn, then you’ll notice a reduction in stopping ability. And if one side has worn more than the other, your car might pull to one side when you hit the brakes.

Depending on the car (and whether all four discs and pads need changing, or just the fronts or rears), this can cost anything between £100 and £1,500. Heavier cars wear their brakes out faster than lighter cars (and have bigger and more expensive brakes in the first place) so they’ll need to have them changed more frequently.

“Your brake discs are warped”

This is another reference to the brakes – specifically, the discs. Their surface should be flat, so if they’ve become warped, they’ll need replacing. A warped disc presents less surface area for the pad to grip and thus reduces braking performance. You’ll also experience an unpleasant juddering sensation when you apply the brakes and the car may also pull to one side.

A warped disc can’t be repaired – you’ll need to get a new one (and a corresponding set of pads). Some work may need to be done on the suspension to make sure the hub (the part that both the brake disc and wheel are attached to) is correctly fitted. New brakes should always be fitted in pairs, to ensure equal braking performance on both sides of the car.

MoT “advisory notices”

When you take your car in for an MoT test, there can be several outcomes. Firstly, your car could pass, meaning no more action is required on your part. Secondly, it could pass, but with some advisory notices. Finally, it could fail (and probably have some advisories, too).

But what is an advisory notice? Essentially, it’s an issue that doesn’t violate the UK’s minimum safety and roadworthiness standards, but one your tester feels is worth attending to, as it could get worse and lead to the car failing its next MoT test.

The most common components to be flagged up in this way are ‘wear-and-tear’ items like brakes and tyres. Bear in mind that passing the MoT test doesn’t necessarily mean your car has a completely clean bill of health, just that its various components meet the minimum required standard. With this in mind, we’d recommend getting any advisories fixed at the earliest opportunity.

Also, bear in mind that MoT testing is pretty well regulated by the DVSA (the Driver and Vehicle Standards Agency), so garages are unlikely to give you unnecessary advisories merely to drum up extra business.

“You’ve got a blown head gasket”

This is a fairly common problem with older cars and can lead to other serious issues. You may be able to have a bash at diagnosing it yourself: if your car is overheating and losing power, and there’s white ‘gunk’ (sometimes called ‘mayonnaise’) under the oil cap, chances are you have a blown head gasket.

But what does this actually mean? All parts of an engine that are joined to one another have a gasket. This is essentially a seal (not unlike the rubber one under the lid of a Tupperware container) that makes sure everything stays airtight and that no fluids mix that shouldn’t (such as oil and water, which results in the ‘mayonnaise’ mentioned above). Depending on the car and the size of the engine, fixing this can either be a fairly simple job, costing maybe £200 (if no further damage has been done) or an expensive one – particularly if you have a bigger engine and further damage has been done as a result of the gasket failing.

“You’ve got a blowing exhaust”

This means there’s a hole somewhere along the exhaust pipe. This could be in the gasket (see above) where the exhaust meets the engine, all the way down to the silencer at the very end of the pipe at the back of the car.

Depending on the size of the hole and where it is, you may notice a reduction in power, but you’re certain to notice more noise, while it may also ‘pop’ more as you slow down.

This isn’t a major problem; depending on where and how big the hole is, you may need a new section of exhaust pipe, or you could just get the hole welded up – as long as it’s small enough. If the exhaust manifold gasket has been holed, then you’ll need a new one of those.

“Your fan belt is slipping”

This means exactly what it says on the tin – a belt under the bonnet is slipping on its pulleys. Confusingly, however, this doesn’t actually have anything to do with the fan. Instead, it’s the belt used to drive the alternator – essentially your car’s electricity generator – that’s not tight enough. This can be for a number of reasons: the belt itself may have worn out and become stretched, or may not have been adjusted correctly.

Again, this is a pretty simple thing to diagnose yourself. At low speeds, or when you’ve just started the engine, you’ll notice a very high-pitched squeaking sound. You may also notice that the lights get dimmer when this happens – because the supply of electricity from the alternator to the battery gets interrupted.

This isn’t catastrophic and shouldn’t be expensive to fix. The part itself is very cheap, so the majority of what you’ll pay will be labour costs – hopefully no more than £100 or so.

“There’s excessive play there”

This phrase is most commonly associated with suspension and steering parts. Essentially, it means something is moving more than it should be (or moving at all when it should be stock still). This is usually a sign of worn suspension or steering components.

This one is a bit trickier to confirm yourself, as the word “excessive” is quite subjective. However, you should be able to detect any suspension or steering problems. You may notice strange noises (often a knocking” or clunking sound) from the wheels. These will be especially noticeable when you’re going around corners or negotiating potholes and speed bumps.

You may also notice the car handling erratically. This could mean it pulls to one side – especially under acceleration – or that the steering no longer feels as direct or accurate as it once did.

How much this will cost to fix is tricky to determine, as it depends on what’s gone wrong. A loose wheel hub is fairly simple (and therefore cheap) to fix, while replacing the whole suspension setup is time-consuming and expensive – it could cost thousands.

“It’s pulling to the left (or right)”

This is a pretty simple one. Essentially, it means that the car veers off to one side without being steered that way. This usually happens either under acceleration or braking – when stronger forces are being put through the wheels and suspension.

Now, like ‘excessive play’ (above) this could indicate a number of issues, specifically to do with the suspension and brakes. These range from the simple and reasonably inexpensive to the complicated and pricey.

“Your timing belt needs replacing”

If your mechanic advises this, then do it – as leaving it could result in either an exceptionally large repair bill or a trip to the scrapyard!

The timing belt links the engine shaft that drives the wheels (the crankshaft) to the shaft that controls the inlet and exhaust vales (the camshaft). Normally, these parts move in a carefully timed sequence (hence ‘timing’) to power the car.

All timing belts have a recommended ‘service life’ (which will be listed in your car’s handbook) and should be changed before they hit their mileage limit. Otherwise, you risk the belt wearing out and snapping. This disrupts the engine’s timing, which can cause extensive damage to important parts inside, such as pistons and valves.

If this happens, you’ll be left at the side of the road waiting for the AA or RAC to rescue you. Depending on the extent of the damage, your engine will either cost a huge amount of money to fix or need to replaced altogether. This means having the timing belt changed is by far and away the cheaper option.

Some modern engines have a timing chain (made of metal and lubricated by the engine’s oil) rather than a timing belt (made of rubber). These don’t need to be replaced at a regular interval and should last the life of the car.

“Your wheels need balancing”

No wheel, no matter how carefully it’s made, is ever perfectly circular – especially when it has a flexible rubber tyre wrapped around it. So in order to make wheels rotate as close to perfectly as possible, small weights occasionally need to be attached to their rim.

If your wheel(s) are out of balance, then you’ll notice vibrations and some rather strange handling, the severity of which increases the more out of balance your wheels are. Fixing this is fairly simple – the wheel and tyre is attached to a machine that spins it and works out how much weight needs to be added. This won’t cost much to do – a maximum of £20.

“Your air-con needs a re-gas”

This means that your air-conditioning system needs a re-fill of refrigerant. This is what evaporates and condenses to draw warmth out of the air that passes though the system, thus cooling it.

Knowing whether or not this needs doing is pretty simple. If you notice your car is losing power and won’t cool air effectively any more, then a re-gas is the most likely solution. Again, this isn’t particularly expensive, starting at around £40 to £50 depending on whether you get it done at an independent garage or a main dealer.

“You’ve got a misfire”

This refers to the combustion process (where fuel is ignited by a spark to drive the engine). It means that one (or more) of your engine’s cylinders is either not firing at all, not firing properly, or firing at the wrong time.

This can be for a couple of reasons: electricity not being sent to the spark plug at the right time, not being sent at all or not enough electricity being sent. The spark plug itself could also be faulty, or the mixture of air and fuel might not be getting into the cylinder at the right time.

A misfire is pretty simple to diagnose: you’ll notice a reduction in power and the engine will sound ominously rough and vibrate far more than usual. A new set of spark plugs won’t cost much, but a problem with the fuel system could be expensive to put right.