Basic Parts of a Car and Their Functions

Cars are intricate machines with various components working together to transport us from one place to another. Understanding the different parts of a car and their functions is essential for both car enthusiasts and everyday drivers. In this article, we’ll take you on a journey under the hood and beyond, exploring the vital components that make your vehicle run smoothly.

The Engine: Heart of the Vehicle

How to fix engine ticking

Cylinder Block and Pistons

The engine’s cylinder block houses precisely machined cylinders where controlled explosions occur. Pistons, tightly fitted within these cylinders using piston rings, move up and down in a rhythmic fashion, harnessing the energy generated by the combustion process. This mechanical energy is the driving force that sets the wheels in motion.

Crankshaft and Camshaft

The crankshaft, a rotating shaft connected to the pistons, converts the linear piston motion into rotational power, carrying it to the transmission where it can be controlled. 

Meanwhile, the camshaft controls the precise timing of the engine’s valves, orchestrating the inflow of air and fuel and the outflow of exhaust gases, ensuring optimal performance. It’s connected to the crankshaft via a timing belt or chain from its placement in the cylinder head, keeping the two synchronized for reliable performance. 

Cylinder Head and Valves

Sitting atop the cylinder block, the cylinder head houses intake and exhaust valves. These valves open and close at specific intervals to regulate the flow of air and fuel into the cylinders and the expulsion of exhaust gases, maintaining the delicate balance required for efficient combustion. 

Intake and Exhaust Manifolds

The intake manifold channels a precisely metered mixture of air and fuel into the cylinders, while the exhaust manifold ushers away spent exhaust gases. These components are vital to ensure the engine receives the right air-fuel mixture and can expel waste gases efficiently. The gases flow through carefully machined channels into and out of the engine block when the respective valves are open, then the valves seal closed to keep the combustion process contained in the cylinder.

Powertrain and Transmission

Transmission Types (Automatic, Manual, CVT)

For all internal combustion engine vehicles, one of three transmission types is installed, connected to the rear side of the crankshaft. No matter the type, this highly complex mechanical system’s purpose is to allow control over the vehicle’s direction and speed through gear changes.

  • An automatic transmission is the most common type. It’s comprised of a complex system of planetary gear sets, hydraulic torque converters, and a series of clutches and bands. These components work together to manage gear selection seamlessly, responding to factors like speed, load, and throttle input. The transmission’s intricate design optimizes power delivery and efficiency, ensuring a smooth and effortless driving experience.
  • A manual transmission, also known as a standard transmission, includes a set of gears, a clutch, and a gear lever. The driver manually selects and engages gears by using the clutch to disengage and re-engage the engine’s power, offering precise control over the vehicle’s speed and power output. This design promotes a more engaged driving experience for enthusiasts.
  • Instead of fixed gears, a Continuously Variable Transmission (CVT) employs a belt or chain system that smoothly and continuously adjusts the transmission ratio, allowing for infinite gear ratios. This design optimizes fuel efficiency and delivers seamless acceleration, resulting in a smooth and responsive driving experience.

Differential and Driveshaft

A differential is designed with a set of gears and pinions within a housing. It splits power from the engine to the wheels, permitting them to rotate at different speeds during turns. This design enables precise control, enhancing stability, traction, and preventing excessive wear on tires and drivetrain components.

The driveshaft transmits power from the transmission to the differential and, subsequently, to the wheels. At one or more points on the driveshaft are u-joints that allow two-axis movement while maintaining the rigidity of the shaft. On 4WD vehicles, there’s a driveshaft from the transfer case to the front differential and another to the rear differential.

Clutch and Torque Converter

In a manual transmission, the clutch serves as the crucial link between the engine and the transmission. It consists of a friction disc pressed against a flywheel using a pressure plate. When the driver depresses the clutch pedal, it disengages the engine from the transmission, allowing for smooth gear changes. This design allows for precise control over power transfer and gear selection.

A torque converter is a key component in an automatic transmission. Its design includes an impeller, a turbine, and a stator, all housed in a sealed unit filled with transmission fluid. As the engine’s crankshaft rotates, the torque converter transmits power to the transmission while allowing the engine to run at idle without stalling. This design ensures smooth and flexible power delivery, enhancing driving comfort.

Fuel and Ignition Systems

Person holding a damaged spark plug in front of an engine.

Fuel Injection System

Modern cars utilize a fuel injection system that delivers precise amounts of fuel directly to each cylinder. Each fuel injector has a nozzle that sprays pressurized fuel directly into the engine’s intake manifold or combustion chamber. This precise delivery ensures optimal air-fuel mixing for efficient combustion, enhancing power output, fuel efficiency, and reducing emissions.

A fuel pump delivers fuel from the tank to the engine’s fuel rail under pressure to feed the fuel injectors constantly. Any fuel that isn’t used is circulated back to the fuel tank via a return line.

Spark Plugs and Ignition Coils

Spark plugs serve as the ignition source, creating a high-voltage spark that ignites the air-fuel mixture within the cylinders. It features a cylindrical body with an electrode at one end. When voltage is applied, it generates an electrical spark across the gap between the electrode and the center conductor. This spark ignites the air-fuel mixture in the engine’s cylinders, initiating combustion.

An ignition coil consists of two coils of wire around an iron core. When the vehicle’s ignition system triggers it, it momentarily stores electrical energy and then rapidly releases it. This high-voltage surge creates a spark at the spark plug, igniting the air-fuel mixture in the engine cylinder, ensuring efficient combustion and engine operation.

Throttle Body and Air Intake System

The throttle body is a component in the air intake system of an engine. It features a butterfly valve that regulates the amount of air entering the engine. When the driver presses the accelerator pedal, the throttle body opens, allowing more air to mix with fuel for increased engine power and acceleration.

The air intake system is designed to provide the engine with a consistent and filtered flow of air. It typically includes an air filter, which removes contaminants, and air intake ducting that directs the clean air  through the intake manifold and into the engine’s combustion chamber. 

Cooling and Lubrication

Radiator and Cooling Fans

The radiator is a heat exchanger used to remove heat from the coolant in the cooling system to prevent your vehicle’s engine from overheating. Hot coolant is routed through the radiator, where the coolant can exchange heat with the passing air.

For general maintenance on your radiator, check your coolant levels twice a year. Replacing a radiator can take most of the day but is a doable DIY job. If you need to replace your radiator, use AutoZone’s how to guide to get the job done right. Additionally, you should reference your vehicle’s repair manual, as each vehicle is slightly different.

The cooling fans draw air through the radiator core and over the engine to whisk away as much heat as possible. The fans could be mechanical if it’s an older car, but most are electric fan motors now. The fan activates when the engine temperature reaches a set point, then it helps to maintain a healthy operating temperature.  

Oil Pump and Oil Filter

The engine oil pump is designed to circulate oil throughout the engine. Typically, it consists of gears or a rotor that draws oil from the oil pan and forces it through the engine’s lubrication system. This constant flow of oil reduces friction between moving parts, ensuring smooth engine operation and longevity.

An engine oil filter is a cylinder designed to trap contaminants from the engine oil as it circulates. Its design includes a porous media that allows oil to pass through while capturing particles like dirt and metal debris. This ensures clean and properly lubricated engine components, extending engine life and performance.

Water Pump and Hoses

A water pump is typically a belt-driven or electric device designed to circulate coolant throughout the engine to maintain optimal operating temperatures. It consists of an impeller that spins, creating a flow of coolant through the engine and radiator. 

Hoses, made of reinforced natural and synthetic rubber and other flexible materials, carry engine coolant between components under the hood such as the thermostat housing, the heater core, and the radiator.

Electrical System

Duralast Gold battery on a shop table in front of an open Nissan Altima.

Battery and Alternator

The battery stores energy in chemical form so it can be released as electricity to run your vehicle’s electrical components. Other terms you may run into when talking about a car battery are:

  • Battery Terminal: A means of connecting the battery to the vehicle’s electrical system. The three types of battery terminals are post or top, side, and L.
  • Battery Capacity: The energy output of a battery measured in amp/hours.
  • Cold Cranking Amps: Abbreviated CCA, this refers to the amount of current that the battery can supply to the vehicle.
  • Group Size: The group size is just what it sounds like, the size of the battery. Common group sizes are: 24, 24F, 25, 34, 35, 51, 51R, 52, 58, 58R, 59, 65
  • AGM: This stands for absorbent glass mat, a design in which sulfuric acid is absorbed by a fiberglass mat, making the battery spill-proof and better at holding a charge.

AutoZone wants to make sure you have the right battery for your vehicle, and you have all the trustworthy advice you need when it comes to batteries.

The alternator is an electricity-generating device that converts mechanical energy to electrical energy in the form of alternating current. It is used to supply power to your vehicle’s electrical system along with the battery. The alternator also recharges the battery using mechanical energy generated by the motion of the vehicle’s parts.

If you notice that your battery is not working and appears to be swollen, your alternator could have a faulty voltage and has overcharged the battery. Stop into your local AutoZone to help you get back on the road.

Starter Motor and Solenoid

An engine starter motor is a compact and powerful electrical motor designed to turn the engine’s crankshaft. When the ignition key is turned, it engages a small gear called a pinion with the engine’s flywheel. The starter motor then spins, cranking the engine to initiate the combustion process and start the vehicle.

The engine starter solenoid is an electro-mechanical switch positioned between the battery and the starter motor. When the ignition key is turned, it receives an electrical signal. The solenoid’s design includes a plunger that moves, connecting the battery to the starter motor, allowing a high current to flow and engage the motor, cranking the engine to start the vehicle.

Wiring Harness and Fuses

The wiring harnesses connect all electrical components, allowing them to communicate and function harmoniously. They’re made of different gauges of wire based on the current load and other factors. Fuses protect the electrical system by breaking the circuit in the event of electrical overloads.

Suspension and Steering

Person showing off a new Duralast loaded strut

Shock Absorbers and Struts

Shocks and struts are essential components of a vehicle’s suspension system, designed to manage ride comfort and stability. Shocks typically consist of a cylinder containing hydraulic fluid with a piston rod inside. Struts combine the shock absorber with a coil spring. 

When a vehicle encounters bumps or irregularities in the road, the shocks and struts dampen the resulting vertical motion by forcing the hydraulic fluid through small passages. This hydraulic resistance converts kinetic energy into heat, effectively reducing the impact felt by the vehicle and its occupants. Properly designed shocks and struts ensure a smoother, more controlled, and comfortable ride, enhancing overall vehicle handling and safety.

Control Arms and Bushings

Control arms, typically shaped like a wishbone, connect the wheel assembly to the vehicle’s chassis at two points for rigid positioning within the wheel well. A ball joint attaches the steering knuckle to the chassis, maintaining the wheel’s vertical position while going over bumps and dips.

Bushings, made of rubber or polyurethane, sit within control arm mounting points and isolate them from vibrations. They allow controlled movement while minimizing road-induced shocks, ensuring stability, precise steering, and ride comfort.

Power Steering Pump and Rack

A power steering pump is designed with a rotary vane or gear mechanism and is typically driven by the engine’s serpentine belt. When the driver turns the steering wheel, the pump pressurizes hydraulic fluid, creating force to assist in turning the wheels. This design enhances steering ease and responsiveness, especially at low speeds and during parking maneuvers.

A power steering gear, also known as a steering rack, contains a set of gears and a rack and pinion mechanism. When the driver turns the steering wheel, the gear converts this rotational motion into linear motion, transferring it to the wheels through tie rods. Hydraulic pressure from the power steering pump assists this process, making steering smoother and more manageable. This design enhances driver control and reduces steering effort, particularly in tight maneuvers.

Braking System

new disc brake parts laying on a table in the shop

Brake Pads and Rotors

When the driver applies the brakes, the brake pads, typically made of friction materials like ceramic or composite, clamp onto the brake rotors, which are metal discs connected to the wheel hub. The friction generated between the pads and rotors converts kinetic energy into heat, slowing the vehicle down. This design ensures effective and controlled braking, with regular maintenance required to ensure optimal performance and safety.

Brake Calipers and Master Cylinder

Brake calipers are essentially hydraulic clamps. When the driver activates the brakes, brake fluid pressure forces the caliper’s pistons to squeeze the brake pads against the rotor, creating friction and slowing down the vehicle. It creates precise and controlled braking, converting kinetic energy into heat and stopping the vehicle safely.

A master cylinder consists of a cylindrical chamber and piston assembly. When the driver applies the brake pedal, it displaces the piston, pressurizing brake fluid within the chamber. This hydraulic pressure is transmitted through brake lines to the calipers, initiating the braking process by forcing the brake pads against the rotors, slowing the vehicle down safely and effectively.

Brake Lines and ABS Module

Brake lines are typically made of steel or flexible rubber and are essential for transmitting brake fluid from the master cylinder to the brake calipers or wheel cylinders. When the driver applies the brakes, hydraulic pressure within the lines ensures that this force is evenly distributed to all four wheels, allowing for controlled and balanced braking, contributing to the vehicle’s safety and stability.

The Anti-Lock Braking System (ABS) module monitors the speed of each wheel. When wheel lockup is detected during hard braking or slippery surfaces, the module momentarily releases and reapplies brake pressure, preventing skidding. This design ensures stable, controlled stops on slippery surfaces, enhancing driver safety.

Exhaust System

Catalytic Converter

A catalytic converter is an emissions control device in a vehicle’s exhaust system. It contains a ceramic substrate coated with precious metals like platinum, palladium, and rhodium. As exhaust gases pass through, these metals facilitate chemical reactions that convert harmful pollutants such as carbon monoxide and nitrogen oxides into less harmful compounds like carbon dioxide and water. This significantly reduces tailpipe emissions, making vehicles more environmentally friendly.

Muffler and Resonator

A muffler, the cylindrical or oval part of the exhaust system you see under the rear of a car, features a series of chambers and baffles. As exhaust gases pass through, the design dissipates sound energy by reflecting and absorbing it. This process reduces noise levels, ensuring a quieter and more comfortable driving experience, while also directing exhaust gases safely out of the vehicle.

A resonator is typically a straight pipe or chamber designed to fine-tune sound frequencies generated by the engine. It works by reflecting sound waves back towards the exhaust gases, canceling out specific noise frequencies. This design helps to achieve a more refined and pleasant exhaust note while minimizing unwanted noise.

Oxygen Sensors

Oxygen sensors, mounted in the exhaust manifold, converter, or exhaust pipe, consist of a ceramic element coated with special materials. They detect the level of oxygen in exhaust gases, transmitting this data to the engine’s computer. By monitoring oxygen content, the engine can adjust the air-fuel mixture for optimal combustion, improving performance, fuel efficiency, and emissions control.

Wheels and Tires

removing tire

Tire Types and Tread Patterns

Passenger vehicles rely on various tire types and tread patterns to meet specific driving needs. 

  • Summer tires, with their smooth and shallow tread, offer excellent traction on dry roads but are less effective in wet or snowy conditions. 
  • All-season tires feature moderate tread depth, providing a balance of performance in diverse weather. 
  • Winter tires, designed with deep, aggressive tread patterns and a flexible rubber compound, excel in snow and ice. 
  • Performance tires prioritize grip and handling, while touring tires emphasize a smooth, comfortable ride. 
  • Off-road tires or truck tires have rugged, deep treads for adventures on rough terrain. 

The choice depends on driving conditions and personal preferences.

Wheel Construction and Alloy vs. Steel

Wheel construction significantly impacts a vehicle’s performance and aesthetics. Wheels can be constructed from steel or lightweight alloys, with designs ranging from simple to intricate. Alloy wheels are preferred for their reduced weight and enhanced appearance, while steel wheels are more durable and budget friendly. Wheel design plays a role in vehicle styling, and different wheel sizes can influence handling and ride quality.

Tire Pressure Monitoring System (TPMS)

TPMS keeps you informed about tire pressure, ensuring they remain properly inflated for safety and fuel efficiency, ultimately enhancing the longevity of your tires. Each tire has a sensor inside, commonly attached to the valve stem, that detects pressure and relays it to a module connected to the vehicle using a radio frequency identification, or RFID. When the pressure is outside of a predetermined threshold, it triggers a TPMS light on the dash. 

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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