Main Car Parts Inside the Bonnet Explained
In today's post, we’ll take a detailed look at a car engine and understand the main components and their functions. Whether you're a car owner or a driver, having basic knowledge about your vehicle's engine is essential. This helps you avoid being misled during repairs and gives you confidence in handling minor issues on your own.
Let’s go step-by-step and understand the key engine components with simple explanations:
Why It's Important to Know Your Car's Engine Parts
1. Battery – Power Source of the Car
The battery is the powerhouse that allows your vehicle to start. It supplies electric current to all electrical components through wiring. You'll see two terminals: one is positive (usually marked red) and the other is negative. Always connect the positive cable to the positive terminal and negative to the negative one to avoid damage.
2. Brake Fluid Reservoir – For Smooth Braking
This small container holds brake fluid, which travels through pipes to apply pressure and engage the brake system. Just below it is the master cylinder, and behind that is the brake booster, which helps reduce the force needed to press the brake pedal.
3. Headlight Relay
This relay ensures proper functioning of the headlights by regulating the electric supply, making sure they shine brightly and consistently.
4. Clutch Cable – Controls Gear Engagement
This cable is connected from the clutch pedal to the gearbox. Pressing the clutch pedal moves this cable, allowing smooth gear changes.
5. Air Filter Box – Purifies Incoming Air
The air filter box houses the air filter, which purifies the air before it enters the engine. Clean air is essential for efficient combustion. The filter traps dust and dirt, preventing it from entering the combustion chamber.
6. Throttle Body – Manages Airflow
This component controls the amount of air entering the engine. When you press the accelerator pedal, the throttle valve opens, allowing more air in, which increases the engine’s speed. It contains a butterfly valve that moves based on pedal input.
7. Thermostat Housing – Maintains Optimal Engine Heat
Inside this housing sits the thermostat valve, which regulates engine temperature. It opens and closes to control coolant flow based on engine heat levels.
8. Alternator – Charges the Battery While Engine Runs
The alternator is responsible for charging the battery while the engine is running. It converts mechanical energy into electrical energy and ensures your battery doesn’t drain.
9. Fan Belt – Drives Key Components
This belt drives several components, including the alternator and radiator fan. The fan helps cool the engine coolant, maintaining optimal temperature.
10. Timing Belt and Gears – Coordinate Camshaft and Crankshaft Rotation
Inside the timing cover lies the timing belt, which synchronizes the rotation of the camshaft and crankshaft. It also drives the water pump, oil pump, and other essential components.
11. Engine Oil Filler Cap- For Oil Refill
This cap is where engine oil is poured in. Proper oil levels are critical for engine lubrication and cooling.
12. Ignition Coil and Spark Plugs – Ignite the Air-Fuel Mixture for Combustion
Ignition coils convert battery voltage into high voltage required to create a spark in the spark plugs, which ignite the fuel-air mixture. Each cylinder has its dedicated spark plug and coil.
13. Exhaust Manifold – Sends burnt gases out of the engine
After combustion, burnt gases exit through the exhaust manifold and flow into the exhaust system, eventually passing through the silencer.
14. Oil Filter – Keeps engine oil clean from dust and metal
The oil filter removes dirt and metal particles from the engine oil, keeping it clean and extending engine life.
15.AC Compressor and Belt – Runs the car AC by moving gas
In some vehicles with AC modifications, like a Gypsy, an AC compressor is driven by a separate belt connected to the crankshaft. It compresses refrigerant and circulates it through the air conditioning system.
16. Charcoal Canister – Catches fuel vapors and reuses them
This component captures fuel vapors and sends them back into the engine when needed, improving mileage and reducing emissions.
17. Car Jack and Handle – Lifts the car for changing tires
The jack is used to lift the vehicle when changing a tire. It’s usually stored under the driver’s seat along with its handle.
18. Windscreen Washer Tank – Stores water to clean the windshield
This container holds water for cleaning the front windshield. When activated, it sprays water to help remove dirt and improve visibility.
19. Coolant Overflow Tank – Holds extra coolant when engine heats up
This tank stores excess coolant. When the engine gets hot, coolant expands and overflows into this container, then returns to the radiator once the engine cools down.
20. Engine Mountings – Hold the engine and reduce vibrations
These metal brackets support the engine and absorb vibrations. There are typically two main mountings: one on the left and one on the right.
21. Oil Pressure Sensor – Warns if oil pressure is too low
This sensor monitors oil pressure and sends signals to your dashboard if levels drop too low—an important warning to prevent engine damage.
22. Dipstick – Lets you check the engine oil level by hand
Used to check engine oil level manually. It’s important to check the oil regularly and refill if it drops below the minimum mark.
23. TPS Sensor – Tells the system how much you press the accelerator
Attached to the throttle body, this sensor monitors throttle valve position and sends data to the ECU to adjust fuel delivery and engine performance.
24. IAC Valve – Controls the engine speed when car is not moving
Regulates the engine’s idle speed by controlling air supply when the throttle is closed (e.g., at startup or during idling).
25. MAP Sensor – Helps balance air and fuel by checking air pressure
This sensor measured air pressure inside the intake manifold and helps optimize air-fuel mixture for combustion.
26. ECT Sensor – Checks coolant temperature to avoid overheating
Monitors coolant temperature and helps the ECU adjust fuel injection and ignition timing.
27. O2 Sensor – Measures oxygen in exhaust for better fuel use
Located in the exhaust manifold, this sensor checks the amount of oxygen in the exhaust gases to ensure optimal fuel mixture and reduce emissions.
28. Engine Number & Gearbox – Shows engine ID and where power transfers
Behind the engine, you'll find the engine number and the start of the gearbox. It includes the flywheel, clutch plate, and pressure plate—critical for transferring engine power to the transmission.
29. Suction Pipe – Pulls clean air into the engine
This pipe draws filtered air into the throttle body. Proper suction ensures optimal engine breathing and power delivery.
30. Fuel Rail and Injectors – Spray fuel into the engine for power
The fuel rail supplies pressurized fuel to the injectors, which then spray it into the combustion chamber. This process is key to generating power.
31. Engine Hoist Points – Spots where the engine is lifted for repairs
These metal hooks or loops are used to lift the engine during maintenance or replacement.
Final Tips for Car Owners
Don’t wait for a breakdown to learn about your car — start with the basics.
Regularly check your engine oil, coolant, and battery terminals.
If you see warning lights on the dashboard, don’t ignore them — they’re there for a reason.
Keep your car manual handy. It’s more useful than you think!
Get your car serviced on time to keep everything running smoothly.
Learn to identify the main engine parts so you can talk confidently with your mechanic.