Car dictionary: automotive terms


Do you want to know what your mechanic or a service adviser is talking about? Here we list some car-related terms with illustrations and explanations. If you cannot find what you are looking for or want to know about something else, let us know. We will add more information.

• Air Flow sensor
• Anti-lock Braking System (ABS)
• Alternator
• Ball joint
• What is Bank 1 or Bank 2?
• Battery
• Charcoal canister
• Check Engine light
• Clutch
• Control arm
• CV joint
• DOHC engine
• Drive belt
• EGR System
• Ground connection
• Head Gasket
• Idle Air Control (IAC) valve
• Mass Air Flow sensor (MAF)
• Misfiring
• OHC engine
• OHV engine
• Overdrive
• Oxygen sensor
• Push rod engine
• Serpentine belt
• Stabilizer bar bushings
• Stabilizer bar link
• Starter
• Starting system
• Thermostat
• Throttle body
• Timing belt
• Timing chain
• Traction Control
• Twin Cam
• Water pump
• Wheel alignment
• Wheel bearing


Anti-lock Braking System (ABS) helps the driver maintain steering control during hard braking, especially in slippery conditions. See this video:



Volkswagen 2.0 TSI engine Alternator
Volkswagen 2.0 TSI engine alternator

An alternator supplies an electric power for the vehicle's electric systems and charges the battery when the engine is running. An alternator is rotated by a drive belt connected to the engine crankshaft.
If the alternator fails, the warning light battery symbol or "CHARGE" icon comes on in the instrument panel.
Alternator problems are common. If the alternator fails it needs to be rebuilt or replaced.

Ball Joint

Ball Joint
Ball joint

A ball joint is a part of a vehicle front suspension. Most cars have one or two ball joints at each front wheel. A ball joint is lubricated inside and sealed with a rubber boot. When a ball joint becomes bad, a vehicle could be unsafe to drive; a ball joint, when badly worn, can separate causing the vehicle to lose control unexpectedly.
One of the possible indication of a bad ball joint could be a knocking noise coming from the front end, particularly while driving over bumps or making sharp turns. If you suspect your vehicle has a bad ball joint or any other suspension component, have your car inspected as soon as you can, it can be unsafe to drive. It's recommended to check the vehicle's chassis in a garage on a lift at least once a year to discover potential problems with suspension, brakes and other components.

Bank 1 or Bank 2

Cylinder banks
Typically, the engine bank that
contains cylinder 1 is called Bank 1

The engine Bank is the group of cylinders aligned together. The term Bank 1 usually refers to the bank of the engine that contains the cylinder number 1.
In an in-line 4-cylinder engine all 4 cylinders are grouped together, so there is only one bank (Bank 1).
A V6 or V8 engine has two banks (see the diagram), each with three or four cylinders respectively. Usually, in a V6 or V8 engine, the bank that contains the cylinder 1 is called Bank 1 and the opposite bank is called Bank 2.


The battery provides electric power to start the car. I get many questions like "My car doesn't start, it only makes a click-click noise when I'm trying to start it" - this is most likely the result of the battery having decided to quit. Unfortunately, usually it happens unexpectedly - the battery just stops working one day. If your vehicle doesn't start and you suspect the battery, there is a simple way to check it. Try switching the wipers on - if they move very slowly, a lot slower than usual (too low voltage) the battery is probably discharged or dead.

Charcoal canister

Charcoal Canister
Charcoal canister

A charcoal canister is a part of the vehicle's Evaporative System. The Evaporative System (EVAP) prevents the fuel vapors from the fuel tank from escaping into the atmosphere. The EVAP system draws the fuel vapors from the fuel tank and temporarily stores them in the charcoal canister. A charcoal canister is filled with charcoal pellets that can absorb fuel vapors. When the engine is running and other conditions allow, the fuel vapors are purged from the charcoal canister into the engine air intake to be burned. The EVAP system is controlled by the engine computer and if there is a problem with the charcoal canister, the Check Engine light will illuminate on the dash.

Control arm

Control arm
Control arm
Lower control arm
Lower control arm. Ford F150

A control arm is a part of the front suspension. Some cars have one control control arm on each side; other vehicles, including many trucks have two (upper and lower) control arms on each side of the front suspension. The internal side of the control arm is connected to a vehicle's body or a frame through the rubber bushings (control arm bushings). An outer end of the control arm holds a ball joint. A ball joint could be bolted to or pressed into the control arm. Sometimes, a ball joint is an integral part of the control arm and if it goes bad the whole control arm must be replaced.
One of the common problems with control arms is when the control arm bushings wear out. Sometimes the bushing can be replaced separately. Typically they have to be pressed into the control arm.
In some cars if the control arm bushings go bad, the whole control arm has to be replaced as it comes as an assembly.
After the control arm bushings or the whole control arm is replaced, the wheel alignment must be performed on most cars.

CV joint

CV Joint boot looks OK
CV joint.

All front-wheel drive cars as well as some four-wheel drive vehicles have Constant Velocity joints or CV joints on both ends of the front drive shafts; the inner CV joints connect the drive shafts to the transmission and the outer CV joints connect the drive wheels to the drive shafts. The CV joints are needed to transfer the torque at a constant speed to the steered wheels as well as to accommodate up and down motion of the suspension. A CV joint is packed with a grease and sealed tight by a rubber or plastic boot. A CV joint doesn't need any maintenance and can last very long, as long as the protective CV joint boot is not damaged. Read full article: CV joint

EGR system

Ford EGR Valve
Ford EGR vacuum-operated valve

The EGR system (Exhaust Gas Recirculation system) is designed to reduce emissions. To be precise, it lowers the amount of nitrogen oxides (NOx) in the exhaust gases.
Nitrogen oxides are formed at very high combustion temperatures. The EGR system re-routes a part of the exhaust gases back into the intake manifold, diluting the air/fuel mixture. As the exhaust gases are not combustible, mixing them with the air/fuel charge helps reduce the combustion temperature.

Ground connection

Ground connection
Ground connection

Whenever a car has some electrical problems, you often hear about a ground connection or 'ground'. Modern cars have a 12-volt electrical system where the positive battery terminal (+12V or 'power') is distributed through wiring and fuses, while the battery negative "-" terminal is connected to the car's body ('ground'); thus a car body acts as a conductor. Most of the electrical consumers in a car receive their positive voltage (+12V) through the fuses and wiring, while the negative side is usually connected to a car body, like the ground terminals in the photo. A bad connection at one of the ground terminals can cause various weird or hard to trace electrical problems. For that reason, with any electrical issues, 'power' (+12V) and 'ground' are usually checked first. Sometimes a ground terminal can get loose or corroded causing poor connection.

Head gasket

Cylinder head V8 engine block Cylinder head Machined surface of the cylinder head Engine coolant mixed with oil

A head gasket is installed between the cylinder head and the engine block. It's not a very expensive part, but it has a very important function: it seals the combustion chambers as well as the oil and coolant passages that run between the engine block and cylinder head.

What causes a blown head gasket? Head gasket failures are often caused by overheating, for example, when the engine is low on coolant (antifreeze) or when the radiator fans don't work. Other reasons include: a detonation (pinging, spark knock), lean air-fuel mixture, design flaws, etc.

Symptoms of a blown head gasket:

Coolant is present in engine oil (engine oil has a "coffee with milk" color ) see the photo.
Engine oil is mixed with coolant (coolant looks dark and dirty with some oil in it).
White steam (smoke) with a strong smell of coolant from the exhaust.
Bubbling in the cooling system.
Coolant boiling over in the overflow tank.
Loss of coolant with no visible leaks.
No start no crank condition due to a hydraulic lock: the starter clicks, but the engine won't turn over because of a hydraulic lock caused by coolant that filled one of the cylinders.

Not all of these symptoms could be present and some of these symptoms could be caused by other problems such as a crack in the cylinder head, leaking intake gasket, etc.

Can a car be driven with a blown head gasket? The short answer is No, because driving with a blown head gasket will cause more damage to the engine. At some point the engine will die and won't start.

Head gasket repair cost: The head gasket repair is quite expensive because of the amount of labor involved. If the engine hasn't been overheated and there is no other damage, the repair could cost $150-$300 for parts, another $150-$300 to have the cylinder head checked and resurfaced, plus $400-$700 for labor.
A new head gasket itself is not very expensive, however many other parts like cam seals, valve cover gasket, intake gaskets often need to be replaced too. If the engine was severely overheated, it might be cheaper to replace the whole engine with a used or rebuilt unit.

What to do if a car has a blown head gasket? Basically, you have three options:
1. To have the engine repaired.
2. To have a used or a rebuilt engine installed.
3. Get rid of the car and buy another one.
You may want to start by getting a few estimates for a head gasket repair from different shops. Inquire about the price for engine replacement too. You also might want to consider how much your car is currently worth, because if it's not much, it may not make financial sense to spend too much money on repairs. If it's an old clunker, a new head gasket won't make it into a new car. You don't want to spend hundreds and hundreds on one repair only to find out that in a few months it will need new brakes, tires and transmission. This actually happens quite often.

How is a blown head gasket diagnosed? Usually a diagnostic involves performing a cooling system pressure test or checking for exhaust gases in the cooling system with a gas analyzer. The compression and cylinder leak-down tests can also tell a lot.

Is it hard to replace a blown head gasket? Replacing a head gasket is a big job, as the cylinder head with manifolds has to come off. Once removed, the cylinder head needs to be tested in a machine shop and re-surfaced if needed. The cylinder block mating surface needs to be checked and cleaned. When a rebuilt cylinder head is installed, the timing may need to be re-set and valves re-adjusted. Check this article for a quick overview of the head gasket replacement steps.

How to prevent head gasket problems: Don't let the engine run low on coolant. Regularly check the coolant level and have it topped up as needed. If you notice a coolant leak or if the engine temperature rises more than normal, have your cooling system checked out in a repair shop.


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