Red Seal Truck and Transport Mechanic flashcards
Red Seal Truck and Transport Mechanic · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Lockout/tagout procedure
- A safety procedure that isolates all energy sources, locks them out, and tags them before repair; verify zero energy at the control point before work begins.
- Torque conversion
- To convert foot-pounds to newton-metres, multiply by 1.3558; to convert newton-metres to foot-pounds, multiply by 0.7376. Always use the fastener's specified unit.
- Safety Data Sheet
- A Safety Data Sheet gives hazard, handling, first-aid, and spill information for a chemical product; keep it accessible and follow it before using the product.
- Diesel compression ignition
- A diesel engine ignites fuel by the heat of highly compressed air, not by a spark plug; compression ratios are typically about 16:1 to 18:1.
- Four-stroke cycle
- Intake, compression, power, and exhaust strokes complete one cycle; the crankshaft turns two revolutions while the camshaft turns one revolution.
- Turbocharger wastegate
- A wastegate bypasses some exhaust gas around the turbine to limit boost pressure; a stuck-closed wastegate can cause overboost and engine damage.
- Cylinder leak-down test
- A cylinder leak-down test supplies compressed air to a cylinder at TDC and measures leakage; listen at intake, exhaust, crankcase, and radiator to locate the leak.
- Ohm's law
- Voltage equals current multiplied by resistance (V = I × R); it is used to calculate expected voltage, current, or resistance in a circuit.
- Series circuit
- In a series circuit, current is the same through every component, total resistance adds, and the sum of voltage drops equals source voltage.
- Parallel circuit
- In a parallel circuit, voltage is the same across each branch, branch currents add to total current, and total resistance is less than the smallest branch resistance.
- CAN bus termination
- A healthy CAN bus typically measures about 60 ohms between CAN high and CAN low with power off, because two 120-ohm terminating resistors are in parallel.
- Governor cut-out pressure
- The air compressor governor cut-out pressure is the maximum system pressure, typically about 120–135 psi; cut-in is usually 20–25 psi lower.
- Spring brake operation
- Spring brakes use stored spring force to apply the parking brake; air pressure compresses the spring to release them, so lost air pressure causes application.
- Slack adjuster stroke
- Pushrod stroke must be measured and compared with the manufacturer's limit for that chamber size; excessive stroke indicates adjustment or component wear.
- Air dryer purge
- The air dryer purge valve expels collected moisture and oil during the compressor unload cycle; a failed purge valve can send water into the air system.
- Pascal's law
- Pressure applied to a confined fluid is transmitted equally in all directions; brake force equals hydraulic pressure multiplied by piston area.
- DOT brake fluid
- DOT 3 and DOT 4 are glycol-based and absorb moisture; DOT 5 is silicone-based and must not be mixed with glycol fluid unless the manufacturer permits it.
- Brake bleeding
- Bleeding removes air from hydraulic brake lines, usually starting at the wheel farthest from the master cylinder; ABS systems may require a scan-tool bleed procedure.
- Positive caster
- Positive caster tilts the steering axis so its top leans rearward; it improves straight-line stability and steering return, but too much increases steering effort.
- Toe-in
- Toe-in means the front edges of the tires are closer together than the rear edges; incorrect toe causes rapid tire wear and steering pull.
- Air suspension ride height
- Ride height must be set to the manufacturer's specification before alignment; incorrect height changes camber, caster, and driveline angles.
- Differential gear ratio
- Divide the number of ring gear teeth by the number of pinion gear teeth; a higher numerical ratio increases torque multiplication and reduces top speed.
- Driveshaft phasing
- U-joint yokes and shafts must be phased and aligned per the manufacturer; incorrect phasing or excessive U-joint angle causes vibration.
- Clutch free play
- Clutch free play is the clearance between the release bearing and pressure plate fingers; too little can cause slippage, too much can cause incomplete release.
- Refrigerant cycle
- Compressor raises refrigerant pressure and temperature; condenser removes heat and condenses it; expansion valve drops pressure; evaporator absorbs cab heat and boils refrigerant.
- Superheat
- Superheat is the temperature of refrigerant vapor above its saturation temperature at a given pressure; it confirms the evaporator is not flooded with liquid.
- Heater core
- The heater core is a small radiator that uses engine coolant to warm air for the cab; a plugged core or stuck blend door causes poor heat.
- SRS service wait
- Before working near airbags, disconnect the battery and wait the manufacturer's specified time, often several minutes, for the backup power to discharge.
- Frame repair rule
- Do not heat, weld, or drill high-strength truck frame rails unless the manufacturer's repair procedure specifically permits it; cracks and loose fasteners require approved repair.
- EGR purpose
- Exhaust gas recirculation sends some exhaust back into the intake to lower combustion temperature and reduce nitrogen oxide emissions.
- DPF regeneration
- A diesel particulate filter traps soot and burns it during regeneration at high exhaust temperature; excessive idling and short trips can prevent passive regeneration.
- SCR and DEF
- Selective catalytic reduction injects diesel exhaust fluid into the exhaust before the SCR catalyst; DEF is about 32.5% urea in water and reduces nitrogen oxides.