Automotive Servicing NC II cheat sheet

5S sequence: Seiri (sort), Seiton (set in order), Seiso (shine), Seiketsu (standardize), Shitsuke (sustain); the first three are physical actions, the last two are discipline controls.

PPE decision rule for the shop floor: safety glasses for any overhead or under-dash work, face shield when grinding or air-blowing, gloves for chemicals and hot parts, steel-toe boots when lifting or jacking.

Hazard communication: the SDS (formerly MSDS) is the single authoritative source for a chemical's flash point, PPE, spill response, and first aid; Section 4 is first aid, Section 8 is exposure controls.

Fire classes and extinguisher choice: Class A ordinary combustibles (water), B flammable liquids (foam, CO2, dry chemical), C energized electrical (CO2, dry chemical, never water), D combustible metals.

Jack safety rule: a hydraulic jack lifts, jack stands support; never place any body part under a vehicle held only by a jack, and chock the wheels opposite the lifted end.

Lockout/tagout: isolate the energy source, apply the lock, verify zero energy by attempting start or testing voltage; one lock and one key per technician.

Communication protocol for a repair order: record customer complaint in the customer's words, then the verified condition, cause, and correction; verbal approvals for extra work must be documented on the RO.

Waste segregation: used oil, coolant, brake fluid, and lead-acid batteries are separate streams; never mix coolant with waste oil or pour either into drains.

Ergonomic and lifting rule: lift with legs, keep load close, and rotate tasks; a two-person lift is required when a component exceeds a comfortable single-person load.

Torque formula: torque = force x lever arm (T = F x L); a 100 N force at 0.3 m gives 30 N·m. Torque wrenches are accurate only in the middle 20-100 percent of their scale.

Micrometer reading: value = barrel (sleeve) reading + thimble reading x least count; a 0-25 mm metric micrometer with 0.01 mm thimble divisions reads sleeve millimetres plus thimble hundredths.

Vernier caliper reading: main scale value + (coinciding vernier line x least count); a 0.02 mm caliper has 50 vernier divisions over 49 main-scale divisions.

Dial indicator and bore gauge measure runout, end play, and cylinder taper; a cylinder is measured at three heights and two directions (thrust and perpendicular) to find taper and out-of-round.

Feeler gauge rule: the correct clearance is the thickest blade that fits with light drag; the next size up must not enter.

Multimeter use: volts measured in parallel with the circuit energized; ohms and continuity measured in parallel with the circuit de-energized and isolated, or readings are false.

Digital tachometer or dwell meter verifies idle speed and, on contact-point ignitions, dwell angle; dwell decreases as point gap increases.

Tool care decision rule: calibrated instruments (torque wrenches, micrometers) go back to zero or lowest setting after use; torque wrenches are never used to loosen fasteners.

Fastener rule: use a six-point socket on a hex fastener and a flare-nut (line) wrench on hydraulic or fuel line fittings to avoid rounding.

Four-stroke order: intake, compression, power, exhaust; the crankshaft makes two revolutions per complete cycle, so camshaft speed is half crankshaft speed.

Compression ratio = (swept volume + clearance volume) / clearance volume; a low reading that rises with a wet test points to rings, a reading that stays low points to valves or head gasket.

Valve clearance is set cold or hot per specification; too little clearance causes hard starting, backfire, and burned valves, too much causes noise and reduced lift.

Cylinder wear limits: taper and out-of-round beyond specification require reboring or replacement; measure with a bore gauge at top, middle, and bottom.

Coolant mixture rule: typically 50/50 coolant and distilled water; too much coolant raises freeze point and lowers heat transfer, too little risks corrosion and freezing.

Thermostat test: suspend in water, heat and check opening temperature with a thermometer; a thermostat stuck open causes slow warm-up and low heater output, stuck closed causes overheating.

Pressure cap rating sets the boiling point; a 1.0 bar cap raises the boiling point of water by roughly 25 degrees Celsius at sea level.

Belt tension rule: deflection measured at the longest span midpoint per specification; a glazed or cracked belt is replaced, not retensioned.

Overheating diagnosis order: coolant level, belt condition, thermostat, radiator fan operation, pressure test for leaks, then combustion gas test for head gasket.

Oil viscosity grade: the first number is cold (W, winter) pumping behaviour, the second is kinematic viscosity at 100 degrees Celsius; a higher second number suits hotter climates and worn engines.

API service category letters increase with newer specifications (for example SJ to SN); always meet or exceed the manufacturer's required category.

Oil pressure low at idle but normal at speed suggests worn bearings or a weak pump; pressure low at all speeds suggests low level, wrong viscosity, or a faulty gauge/sender.

Fuel system pressure test: connect gauge at the service port, compare key-on prime pressure, running pressure, and pressure after 10 minutes (leak-down) to specification.

Fuel injector flow balance: injectors within a small percentage of each other; a lean misfire on one cylinder with good spark points to a clogged or shorted injector.

Air-fuel ratio: stoichiometric for gasoline is about 14.7:1 by mass; rich means excess fuel (black smoke, high CO), lean means excess air (high NOx, lean misfire).

Diesel injection timing too advanced causes knock and high NOx; too retarded causes white smoke, poor power, and high fuel consumption.

Fuel filter replacement direction rule: observe the flow arrow; a reversed filter restricts flow and can damage a high-pressure pump.

Common-rail diesel: rail pressure is generated by the high-pressure pump and controlled by the pressure control valve and injector timing; never crack high-pressure lines while running.

Ohm's law: V = I x R; power P = V x I. A 12 V circuit drawing 5 A has 2.4 ohms resistance and dissipates 60 W.

Series circuit: current is the same everywhere, voltages add; parallel circuit: voltage is the same, currents add. Most vehicle loads are wired in parallel.

Voltage drop test rule: measure across the conductor or connection while the circuit is loaded; more than about 0.5 V drop on a 12 V power or ground circuit indicates excessive resistance.

Battery: 12.6 V at rest is fully charged (2.1 V per cell x 6); 12.4 V is about 75 percent, 12.0 V about 25 percent. Load test or conductance test confirms capacity.

Alternator output: typically 13.8-14.5 V at the battery with engine running and loads on; below 13.2 V suggests a faulty alternator, regulator, or belt.

Starter current draw: high current with slow cranking suggests a seized or shorted starter or bad ground; low current with no cranking suggests an open control circuit or faulty relay.

Charging system ripple test: excessive AC ripple across the battery with the engine running indicates a failed alternator diode.

Lighting circuit rule: a bulb with power and ground but no light is faulty; no power at the bulb means trace back through switch, relay, and fuse; check the ground first for dim or intermittent lamps.

Fuse rating rule: replace with the same rating; a fuse that blows repeatedly indicates a short to ground, not a fuse problem.

Hydraulic principle: pressure is equal throughout a closed system (Pascal's law); force = pressure x piston area, so a larger wheel-cylinder bore gives more force but less travel.

Brake fluid: DOT 3 and DOT 4 are glycol-based and hygroscopic (absorb moisture, lowering boiling point); DOT 5 is silicone-based and must not be mixed with glycol fluid.

Bleeding sequence rule: start at the wheel farthest from the master cylinder and work toward the nearest; keep the reservoir topped up to avoid air ingestion.

Disc runout and thickness: measure rotor thickness with a micrometer at several points and compare with the minimum thickness cast on the rotor; measure runout with a dial indicator.

Pad and lining rule: replace axle sets together; a low pad with uneven wear on one side points to a sticking caliper slide or seized piston.

Pedal feel diagnosis: spongy pedal means air in the system; low, sinking pedal means internal master-cylinder bypass; hard pedal means a booster or check-valve fault.

Parking brake adjustment: adjust at the rear brake mechanism first, then the cable; dragging brakes cause heat, blue rotors, and poor fuel economy.

ABS warning lamp: a lamp on after start indicates a fault stored in the ABS module; a wheel-speed sensor with an erratic signal can cause low-speed activation.

Brake hose and line rule: flexible hoses must not bulge or crack; rigid lines must be double-flared, never single-flared, and routed away from heat and moving parts.

Alignment angles: camber is the inward or outward tilt of the wheel viewed from the front; caster is the forward or rearward tilt of the steering axis; toe is the difference in distance between the front and rear of the tires.

Positive camber wears the outer tire edge; negative camber wears the inner edge; incorrect toe causes feathered edge wear across the tread.

Caster does not wear tires but affects straight-line stability and steering return; too little caster causes wander, too much causes heavy steering.

Toe setting rule: set toe last, after camber and caster, and with the steering wheel centered and the vehicle at curb weight.

Thrust angle is the bisector of the rear toe; a non-zero thrust angle causes the steering wheel to be off-center and dog-tracking.

Wheel balance: static imbalance causes vertical hop, dynamic imbalance causes shimmy; balance is measured in grams and corrected with clip-on or adhesive weights.

Tire inflation and wear: underinflation wears both shoulders, overinflation wears the center; a wear pattern on one side only points to alignment or a bent suspension component.

Shock absorber test: bounce the corner and release; more than one rebound oscillation indicates a worn damper. Leaking fluid is a replacement criterion.

Steering free play and tie-rod check: check inner and outer tie rods for play with the wheel off the ground; excessive free play must be corrected before alignment.

Manual clutch operation: the release bearing pushes the diaphragm spring, which releases clamping force on the disc; free play must allow the bearing to fully retract.

Clutch slip versus drag: slip shows as engine speed rising without vehicle speed; drag shows as difficulty engaging gears and creeping with the pedal down.

Manual transmission gear ratio = driven gear teeth / driving gear teeth; overall ratio is gearbox ratio x final drive ratio.

Automatic transmission fluid check: level checked at operating temperature with the engine running and the selector in Park or Neutral per the manufacturer's procedure; color and smell indicate condition.

Torque converter: multiplies torque at low speed through the stator; a stall test compares engine speed at full throttle in gear against specification to reveal converter or engine faults.

CV joint diagnosis: a clicking noise on turns indicates an outer CV joint; a vibration under acceleration indicates an inner joint or a worn intermediate shaft.

Differential rule: hypoid gears require limited-slip or hypoid-rated lubricant; using the wrong additive causes chatter and accelerated wear.

Driveshaft phasing: universal joints must be phased so yokes align; incorrect phasing causes vibration that increases with speed.

Final drive and bearing preload: set pinion bearing preload with a torque gauge in inch-pounds per specification; too much preload overheats the bearing.