Cars: How They Work and How to Fix Them

What this course is

Written for teens and adults with no car experience. It picks up where the car guides in Being an Adult 101 leave off. Each lesson explains the “why” as well as the “what”: the physics of a hydraulic brake, the chemistry of a catalytic converter, the math of gears. Facts and numbers come from U.S. government agencies, university automotive and engineering programs, OpenStax textbooks and ASE, and every lesson lists its sources.

How to use it

1. Start with Lesson 1 for the big picture, then go in order or jump to the system you’re curious about.
2. Each lesson has diagrams, a “parts and what they do” table, a short quiz and links to go deeper. Badges show the level.
3. Play with the interactive pieces: the running engine, the brake hydraulics, the differential, the cooling system and more.
4. Use the troubleshooting finder when something seems wrong, and climb the skill ladder one rung at a time.

Map of the car

Every system, drawn inside one car. Point at a system or its name to see what it does; click to open its lesson.

The lessons

1. 1 🗺️ The Big PictureHow a car turns fuel or electricity into motion, and a map of every system. Beginner7 min✓ Done
2. 2 ⚙️ The EngineThe four-stroke cycle and every main part, plus displacement, compression, horsepower and torque. Beginner10 min✓ Done
3. 3 🔥 Air, Fuel and SparkIntake, sensors, fuel delivery, ignition and the engine computer’s closed loop; how diesels differ. Advanced6 min✓ Done
4. 4 🌡️ Cooling and LubricationRadiator, water pump, thermostat, coolant and heater core; oil pump, filter, passages and pressure. Beginner9 min✓ Done
5. 5 💨 Exhaust and EmissionsManifold, catalytic converter, oxygen sensors, muffler, EGR, EVAP, OBD-II and reading codes. Intermediate8 min✓ Done
6. 6 🔋 The Electrical SystemBattery, alternator, starter, fuses and relays, grounds, reading simple wiring, safe multimeter checks. Intermediate7 min✓ Done
7. 7 ⚙ Transmission and DrivetrainGears and torque, clutch and manual gearbox, automatics, CVTs, driveshafts, differentials and drive layouts. Advanced9 min✓ Done
8. 8 🛑 BrakesHydraulics and Pascal’s principle, master cylinder, lines, calipers, pads, rotors, drums, fluid, ABS and regenerative braking. Intermediate9 min✓ Done
9. 9 🛞 Steering, Suspension and AlignmentRack and pinion, power steering, springs, shocks and struts, control arms, ball joints, tie rods, sway bars, camber, caster and toe. Intermediate5 min✓ Done
10. 10 ⭕ Wheels and Tires in DepthThe sidewall code, load index and speed rating, TPMS, wear patterns and what they mean, rotation and balancing. Beginner8 min✓ Done
11. 11 ⚡ Hybrids and Electric CarsBattery pack, inverter, motor, regenerative braking, charging levels, and why high voltage is for trained technicians. Intermediate5 min✓ Done
12. 12 🚀 Thrusters and Fans on the 2026 RoadsterTesla’s 2026 Roadster: cold-gas thrusters and suction fans, from Newton’s third law to choked flow and downforce, with two simulators. Advanced15 min✓ Done
13. 13 🔎 Troubleshooting by SymptomAn interactive finder: pick a symptom, answer a question or two, and get likely causes, safe checks and when to stop. Beginner5 min✓ Done
14. 14 🧰 Doing Your Own WorkA basic tool kit, garage safety, and a skill ladder from first jobs to the jobs to leave to professionals. Beginner5 min✓ Done
15. 15 🧑‍🔧 Careers in Auto RepairWhat automotive service technicians do, how they train, what they earn, the job outlook, and ASE certification. Beginner4 min✓ Done

Troubleshooting finder

Something seems wrong? Pick a symptom, answer a question, and see the likely causes, what you can safely check, and when to stop driving. Lesson 13 explains how to think it through.

The skill ladder

Build skill one rung at a time, with an experienced helper and the service information the first time you do anything new. Lesson 14 covers tools and garage safety.

1. 1

   First jobs

   Checks and simple swaps. No lifting the car, few tools.

   • Check your engine oil
   • Check tire pressure and tread
   • Check coolant, brake fluid and washer fluid
   • Replace wiper blades
   • Read dashboard warning lights
   • Jump-start a car
   • Change a flat tire
   • Check battery voltage with a multimeter
   • Read trouble codes with a scan tool
2. 2

   Next steps

   Basic tools, the owner’s manual, and an experienced helper the first time.

   • Change your own oil and filter
   • Replace the engine air filter
   • Replace the cabin air filter
   • Replace a headlight, taillight or turn-signal bulb
   • Clean battery terminals; replace a 12-volt battery
   • Replace a blown fuse with the same rating
   • Rotate the tires (if your manufacturer recommends it)
3. 3

   Intermediate jobs

   Service information, torque specs, jack stands, and a mentor. Mistakes here can be costly or unsafe.

   • Brake pads and rotors
   • Spark plugs and ignition coils
   • Drive belts
   • Coolant drain and refill
   • Shock absorbers (not struts with springs under load)
   • Simple sensor replacement after diagnosis
4. 4

   Leave these to professionals

   They need training, certification or equipment a home garage doesn’t have.

   • Airbags and anything in the airbag system (NHTSA: never take apart the steering wheel or airbag yourself)
   • High-voltage hybrid and EV parts: battery, orange cables, inverter (NHTSA)
   • A/C refrigerant: EPA requires certified technicians and approved equipment for paid service, and venting refrigerant is prohibited
   • Wheel alignment (special equipment and a qualified technician)
   • Mounting and balancing tires
   • Internal engine and transmission repair; timing belts and chains
   • Struts with coil springs, steering racks, brake hydraulics and ABS units
   • Fuel system leaks and fuel-line repairs

Careers

Automotive service technicians and mechanics inspect, maintain and repair cars and light trucks. Here are the U.S. Bureau of Labor Statistics figures from its Occupational Outlook Handbook (page updated August 27, 2026):

Technicians typically complete a program in automotive service technology at a high school, community college or technical institute; others train through manufacturer programs, apprenticeships or on the job, and certification may be required. Lesson 15 has the details, the training paths and how ASE certification works.

Sources

Each lesson lists the sources for its own facts. Here they all are in one place.