🛑 CRITICAL PASS/FAIL: The In-Cab Air Brake 4-Step Test (Must Do in Exact Sequence)
1. Static Applied Leakage Test
Chock wheels, release tractor/trailer brakes, turn engine OFF. Hold foot brake 1 full minute. Max allowed air drop: Single vehicle ≤ 3 PSI/min • Combination ≤ 4 PSI/min.
2. Low Air Warning Signal Test
Ignition key ON, engine off. Fan foot brake pedal repeatedly. Low air warning buzzer and light must activate at or above 55 to 60 PSI.
3. Emergency Spring Brake Pop-Out
Continue fanning brake pedal until the red and yellow dash valves pop out. Both parking valves must pop out between 20 and 45 PSI.
4. Parking & Service Brake Check
Start engine, build air to governor cut-out (120-140 PSI). Gently pull against yellow knob, then red knob, then drive 5 MPH and apply service brake (no pulling).
Zone 1: Engine Compartment
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Oil & Coolant Levels: Dipstick above add mark. Coolant reservoir between min/max, cap tight.
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Alternator & Water Pump: Belt-driven (or gear). Belt has max 1/2" to 3/4" play at center. No frayed wires.
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Air Compressor & Power Steering Pump: Gear-driven, mounted securely, no audible air or oil leaks.
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Steering Box & Linkage: Pitman arm, drag link, tie rod — castle nuts and cotter pins locked in place.
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Front Suspension (Springs & U-bolts): Leaf springs not shifted, cracked or missing. U-bolts tight, no loose nuts.
Zone 2: In-Cab Inspection
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Safety Equipment (Emergency Gear): Fully charged 10 B:C fire extinguisher (gauge in green), 3 red triangles, spare fuses.
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Windshield & Wipers: Glass clean, no cracks over 1". Blades flexible, wiper fluid pumps properly.
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Horns (City & Air Horn): Test electric city horn (steering wheel) and ceiling air horn lanyard.
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Heater & Defroster: Check warm air blower from floor vents and windshield defroster louvers.
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Seatbelt & Mirrors: Latches securely, webbing not frayed. Mirrors adjusted clean for driver.
Zone 3: Coupling & Fifth Wheel
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Air & Electric Lines (Gladhands): 7-way plug locked. Gladhands locked at 90°, rubber grommets not dry-rotted.
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Fifth Wheel Skid Plate & Apron: Properly greased, no daylight between apron and fifth wheel.
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Locking Jaws & Kingpin: Jaws fully closed around kingpin shank (visual check with flashlight).
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Release Arm & Safety Latch: Release handle in locked forward position, safety latch engaged.
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Landing Gear & Crank Handle: Fully raised, pads free of debris, crank handle stowed securely in bracket.
Zone 4: Running Gear & Brakes
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Brake Chamber & Slack Adjuster: Pushrod has ≤ 1 inch manual play when brakes released. Clamps tight.
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Brake Drums & Linings: Linings at least 1/4" thick, not oil-soaked or glazed. Drum free of cracks.
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Tires (Steer vs Drive/Trailer): Steer: min 4/32" tread, no recaps. Drive/Trailer: min 2/32" tread. 100-110 PSI.
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Lug Nuts & Wheel Rims: All present and tight. No rust trails (loose nut) or shiny metal (cracked rim).
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Hub Oil Seal: Oil level visible in sight glass, rubber plug secure, no leaks.