Auto Repair Glossary

Braking & Safety

ABS (Anti-lock Braking System)

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Location: Sensors at each wheel, connected to a control module under the hood.

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ABS keeps your wheels from locking up during hard braking. When you slam on the brakes, it quickly pulses brake pressure so your tires keep gripping the road. That helps you steer while stopping, especially on wet or icy roads. If an ABS warning light comes on, the system may need diagnosis.

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Brake Pads

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Location: Inside the brake caliper, pressed against the brake rotors at each wheel.

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Brake pads create the friction that slows your car down. When you press the brake pedal, the pads squeeze against the spinning rotor to stop the wheel. They wear down over time and need replacing regularly to keep stopping power strong and safe. Squeaking, grinding, or longer stopping distances are common signs that your brake pads are due for service.

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Brake Rotors

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Location: Mounted directly behind each wheel, attached to the wheel hub.

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Brake rotors are smooth metal discs that spin with your wheels. When you press the brake pedal, the pads clamp onto the rotors to stop the vehicle. Warped or worn rotors can cause vibration, pulsing in the pedal, or reduced braking performance.

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Caliper

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Location: Bolted over the brake rotor at each wheel.

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The brake caliper houses the brake pads and squeezes them against the rotor when you press the pedal. It uses hydraulic pressure from the brake fluid to create stopping force. A sticking or leaking caliper can cause braking to feel uneven or weak, leading to pulling, uneven tire wear, or reduced stopping power.

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Master Cylinder

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Location: Under the hood, mounted near the firewall in front of the driver’s seat.

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The master cylinder converts the force from your brake pedal into hydraulic pressure, sending brake fluid through the brake lines to activate the calipers at each wheel. If it fails, you may notice a soft or sinking pedal, fluid leaks, or reduced stopping power.

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Brake Lines

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Location: Runs along the frame of the vehicle, from the master cylinder to each wheel.

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Brake lines are metal tubes and flexible hoses that carry brake fluid throughout the braking system. When you press the brake pedal, hydraulic pressure moves fluid through these lines to activate the calipers at each wheel. Leaks or corrosion in the lines can reduce stopping power. Rust, cracks, or damage can lead to a spongy brake pedal or even sudden loss of braking performance and should be repaired immediately.

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Brake Fluid

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Location: Stored in a reservoir on top of the master cylinder under the hood.

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Brake fluid is a hydraulic fluid that transfers force from the brake pedal to the brakes at each wheel. It operates under high pressure and high temperatures. Over time, brake fluid absorbs moisture, which can reduce performance and contribute to corrosion inside the system. Replacing it at recommended intervals helps maintain consistent stopping power and protects internal components.

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Parking Brake

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Location: Activated by a hand lever, foot pedal, or electronic switch, and connected to the rear brakes.

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The parking brake prevents your vehicle from rolling when parked. It operates through a cable or electronic system that is separate from the primary hydraulic braking system. It is especially important when parking on hills and can serve as an emergency backup in certain situations. If it does not hold the vehicle in place or fails to fully release, it should be inspected to avoid potential rear brake damage.

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Engine & Performance

Alternator

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Location: Under the hood, usually mounted to the front of the engine and driven by the serpentine belt.

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The alternator generates electricity while your engine runs. It powers your vehicle’s electrical systems and keeps the battery charged. If it fails, your car can stall or refuse to start. Signs of trouble include dim lights, battery warning lights, or a dead battery.

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Catalytic Converter

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Location: Part of the exhaust system, underneath the vehicle between the engine and muffler.

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The catalytic converter reduces harmful emissions by converting exhaust gases into less harmful pollutants. It’s essential for passing emissions tests. A failing converter can cause sluggish acceleration, rattling noises, or a check engine light.

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Head Gasket

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Location: Sandwiched between the engine block and cylinder head.

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The head gasket seals the engine’s combustion chambers and keeps oil and coolant from mixing. It also helps maintain proper engine pressure. Signs of failure include overheating, white exhaust smoke, milky oil, or coolant loss with no visible leak.

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Oxygen (O2) Sensor

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Location: Threaded into the exhaust system, before and sometimes after the catalytic converter.

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The O2 sensor measures oxygen levels in the exhaust to help the engine adjust fuel mixture for efficiency and emissions. It plays a big role in fuel economy. A bad sensor can cause poor gas mileage, rough running, or trigger the check engine light.

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Timing Belt / Chain

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Location: Inside the front of the engine, covered by a protective timing cover.

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The timing belt or chain keeps the crankshaft and camshaft synchronized so the engine’s valves open and close at the correct moments. Proper timing is essential for smooth operation and performance. Timing belts typically require replacement between 60,000 and 100,000 miles, depending on the manufacturer. If a timing belt fails, it can result in severe engine damage, especially in interference engines.

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Ignition Coil

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Location: Mounted on or near the engine, often directly on top of each spark plug.

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The ignition coil transforms battery voltage into the high voltage needed to fire the spark plugs. It’s key to starting and running smoothly. A failing coil can cause misfires, rough idling, poor acceleration, or a flashing check engine light.

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Fuel Injector

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Location: Mounted on the engine, connected to the fuel rail, and spraying into each cylinder.

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Fuel injectors spray a fine mist of fuel into the engine for combustion. They help balance power and fuel efficiency. Clogged or failing injectors can cause rough idling, hesitation, poor fuel economy, or hard starting.

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Spark Plugs

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Location: Threaded into the engine’s cylinder head, one per cylinder.

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Spark plugs ignite the air-fuel mixture inside the engine to create power. They’re small but critical to performance. Most spark plugs need replacement between 30,000 and 100,000 miles, and worn plugs can cause misfires, poor mileage, or slow starts.

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Air Filter

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Location: Inside a plastic housing under the hood, connected to the engine’s air intake system.

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The air filter keeps dirt and debris from entering your engine. Clean air helps your engine run efficiently and last longer. It’s typically replaced every 15,000 to 30,000 miles, or sooner if dirty, and a clogged filter can reduce performance.

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Serpentine Belt

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Location: Wrapped around multiple pulleys at the front of the engine.

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The serpentine belt powers important components like the alternator, power steering pump, and air conditioning compressor. It keeps several systems running at once. Cracks, squealing noises, or visible wear mean it’s time for inspection or replacement.

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Crankshaft

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Location: Inside the lower part of the engine block.

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The crankshaft converts the up-and-down motion of the pistons into rotational motion that turns your wheels. It’s a core engine component. Problems are rare but serious—knocking noises, low oil pressure, or engine vibration need immediate attention.

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Camshaft

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Location: Inside the engine cylinder head, above the valves.

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The camshaft controls when the engine’s intake and exhaust valves open and close. It works closely with the timing belt or chain. Symptoms of camshaft issues include rough idling, poor performance, backfiring, or a persistent check engine light.

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Steering & Suspension

Ball Joints

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Location: Connecting the control arms to the steering knuckles at each front wheel.

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Ball joints act like pivot points between your wheels and suspension. They allow the wheels to move up and down while also turning left and right. They carry a lot of weight and movement. Clunking noises, uneven tire wear, or loose steering can signal worn ball joints.

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Shock Absorbers

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Location: Mounted behind each wheel, connected between the suspension and vehicle frame.

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Shock absorbers control the up-and-down movement of your vehicle’s springs. They keep your ride smooth and your tires planted on the road. Without good shocks, your vehicle can bounce excessively. Leaking fluid, nose-diving when braking, or excessive bouncing are signs they’re worn out.

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Struts

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Location: Integrated into the suspension assembly at each wheel, usually in the front and sometimes rear.

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Struts combine a shock absorber and structural support in one unit. They help maintain ride height, stability, and handling. Because they’re load-bearing, they’re critical to alignment. Clunking noises, uneven tire wear, or a rough ride often mean struts are due for replacement.

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Tie Rods

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Location: Connected between the steering rack and the steering knuckle at each front wheel.

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Tie rods link your steering system to your wheels. When you turn the steering wheel, tie rods push or pull the wheels to change direction. They’re essential for precise steering control. Loose steering, uneven tire wear, or knocking sounds when turning can point to worn tie rods.

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Control Arm

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Location: Attached between the vehicle frame and the steering knuckle at each front wheel.

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Control arms connect the suspension to the frame and allow controlled wheel movement. They help keep your tires properly positioned during driving. Clunking over bumps, pulling to one side, or uneven tire wear can signal a worn control arm or bushings.

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Sway Bar Links

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Location: Connecting the sway bar to the suspension near each wheel.

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Sway bar links connect the sway bar to your suspension and help reduce body roll when turning. They keep your vehicle feeling stable around corners. Rattling noises over bumps or excessive leaning in turns are common signs of worn sway bar links.

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Power Steering Pump

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Location: Mounted on the engine and driven by the serpentine belt.

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The power steering pump creates hydraulic pressure to make steering easier. Without it, turning the wheel would take much more effort. Whining noises, stiff steering, or fluid leaks near the pump can mean it’s failing.

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Power Steering Fluid

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Location: Stored in a reservoir under the hood, connected to the power steering system.

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Power steering fluid transfers hydraulic pressure that helps you turn the wheel smoothly. It also lubricates system components. Low fluid levels, dark or dirty fluid, whining noises, or stiff steering mean it’s time for inspection or service.

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Wheel Alignment

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Location: Refers to the angles of the wheels and suspension system.

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Wheel alignment adjusts the angles of your tires so they meet the road correctly. Proper alignment improves handling, tire life, and fuel efficiency. If your vehicle pulls to one side or your steering wheel sits crooked, it’s time for an alignment check.

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Bushings

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Location: Found throughout the suspension system between metal components.

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Bushings are rubber or polyurethane cushions that reduce friction and absorb vibration between suspension parts. They help keep your ride quiet and controlled. Cracking noises, excess vibration, or loose-feeling handling often point to worn suspension bushings.

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Drivetrain & Transmission

CV Joint / Axle

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Location: Connecting the transmission to each drive wheel, typically in front-wheel and all-wheel drive vehicles.

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CV (constant velocity) joints allow the axle to transfer power to the wheels while flexing with suspension movement and turns. They keep power flowing smoothly. Clicking when turning, grease around the tire, or vibration during acceleration can mean a worn CV joint.

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Differential

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Location: Between the drive wheels, found in the front, rear, or both, depending on the vehicle.

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The differential allows your drive wheels to spin at different speeds when turning. Without it, corners would feel jerky and hard on your tires. It also transfers power from the driveshaft to the wheels. Whining noises, fluid leaks, or vibration can signal differential trouble.

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Transmission Fluid

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Location: Inside the transmission, with a dipstick or fill port under the hood or beneath the vehicle.

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Transmission fluid lubricates, cools, and helps transfer power inside the transmission. In automatic vehicles, it also acts as a hydraulic fluid. Burning smells, slipping gears, delayed shifting, or dark fluid mean it’s time for service. Regular changes help extend transmission life.

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Transfer Case

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Location: Attached to the transmission in four-wheel drive (4WD) or all-wheel drive (AWD) vehicles.

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The transfer case splits power between the front and rear axles in 4WD and AWD vehicles. It helps improve traction in slippery conditions. Grinding noises, difficulty shifting into 4WD, or fluid leaks are signs that it needs attention and regular fluid service.

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Transmission Filter

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Location: Inside the transmission, typically accessible by removing the transmission pan.

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The transmission filter traps dirt and debris from the transmission fluid. Keeping the fluid clean helps protect internal components. If clogged, you may notice slipping gears or delayed shifting. It’s commonly replaced during a transmission fluid service.

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Universal Joint (U-Joint)

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Location: Along the driveshaft, connecting it to the transmission and differential.

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U-joints allow the driveshaft to flex while transferring power from the transmission to the differential. They handle constant movement and torque. Clunking when shifting, vibration at highway speeds, or squeaking noises can point to a worn U-joint.

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Clutch

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Location: Between the engine and transmission in manual transmission vehicles.

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The clutch connects and disconnects engine power to the transmission when you press the clutch pedal. It allows you to change gears smoothly. Slipping, difficulty shifting, or a burning smell during driving are common signs that the clutch is wearing out.

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Flywheel

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Location: Bolted to the back of the engine, between the engine and transmission.

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The flywheel is a heavy metal disc that helps smooth engine rotation and provides a surface for the clutch to grip. It keeps power delivery steady. Vibration, clutch chatter, or grinding noises during shifting can signal flywheel wear or damage.

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Cooling & Climate

AC Compressor

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Location: Mounted to the front of the engine and driven by the serpentine belt.

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The AC compressor pressurizes and circulates refrigerant through your air conditioning system. It’s what makes cold air possible on a hot day. Without it, your AC won’t cool. Warm air from the vents, loud squealing, or the AC not turning on can signal compressor trouble.

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Radiator

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Location: At the front of the vehicle, behind the grille.

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The radiator removes heat from the engine by circulating coolant through thin metal fins that release heat into the air. It keeps your engine from overheating. Coolant leaks, overheating, or visible corrosion can mean the radiator needs repair or replacement.

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Thermostat

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Location: Between the engine and radiator, inside the cooling system housing.

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The thermostat controls coolant flow based on engine temperature. It stays closed while the engine warms up, then opens to allow coolant to circulate. If stuck, your engine may overheat or run too cool, often triggering a check engine light.

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Water Pump

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Location: Bolted to the front of the engine, usually driven by the timing belt or serpentine belt.

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The water pump circulates coolant throughout the engine and radiator. It keeps coolant moving so heat can be carried away. Coolant leaks near the front of the engine, overheating, or whining noises can signal a failing water pump.

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Heater Core

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Location: Inside the dashboard, behind the glove box area.

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The heater core uses hot engine coolant to create warm air for your cabin heat. It works like a small radiator inside your dash. Foggy windows, a sweet smell inside the cabin, or damp passenger floorboards can point to a leaking heater core.

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Condenser

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Location: Mounted in front of the radiator, behind the grille.

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The condenser releases heat from the refrigerant after it leaves the AC compressor. It helps turn hot gas into cooled liquid, so your system can produce cold air. Weak cooling, refrigerant leaks, or damage from road debris can cause condenser problems.

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Antifreeze / Coolant

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Location: Stored in the radiator and coolant reservoir under the hood.

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Coolant is a temperature-regulating fluid that prevents overheating in summer and freezing in winter. It also protects against corrosion inside the engine. Low levels, discoloration, or overheating mean it’s time for inspection. Most vehicles need coolant service every 2–5 years.

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General Maintenance & Tech

Cabin Air Filter

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Location: Behind the glove box or under the dashboard, inside the HVAC system.

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The cabin air filter cleans the air coming into your vehicle’s interior through the heating and air conditioning system. It traps dust, pollen, and debris before you breathe it in. Weak airflow or musty smells usually mean it’s time to replace it, typically every 15,000 to 30,000 miles.

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Diagnostic Trouble Code (DTC)

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Location: Stored in the vehicle’s onboard computer system.

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A Diagnostic Trouble Code is a code your vehicle generates when it detects a problem. These codes trigger the check engine light and help technicians pinpoint issues quickly. If your check engine light comes on, scanning for DTCs is the first step toward finding the cause.

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TPMS (Tire Pressure Monitoring System)

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Location: Sensors mounted inside each wheel, connected to the vehicle’s computer.

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TPMS monitors the air pressure in your tires and alerts you if one gets too low. Proper tire pressure improves safety, fuel economy, and tire life. A dashboard warning light usually means a tire is low, a sensor battery is failing, or a sensor needs service.

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VIN (Vehicle Identification Number)

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Location: Visible on the dashboard near the windshield and inside the driver’s door jamb.

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The VIN is your vehicle’s unique 17-character identification number. It tells the story of where the vehicle was built, its engine type, and specific features. You’ll need the VIN for registration, recalls, insurance, and ordering the correct replacement parts.

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Oil Viscosity

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Location: Refers to the engine oil inside your engine.

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Oil viscosity describes how thick or thin motor oil is at certain temperatures, shown as numbers like 5W-30. The right viscosity protects engine parts and keeps oil flowing properly. Using the wrong oil can affect performance and wear, so always follow the manufacturer’s recommended grade.

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Chassis

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Location: The vehicle’s main frame underneath the body.

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The chassis is the structural foundation of your vehicle. It supports the engine, suspension, steering, and body. Think of it as the skeleton everything else attaches to. Rust, structural damage, or excessive corrosion underneath the vehicle should be inspected to maintain safety and stability.