MT CDL Air Brakes case studies
MT CDL Air Brakes · Put your knowledge to work in context.
The Montana CDL air brakes knowledge test is the written portion of the air brake endorsement requirement for drivers who operate vehicles equipped with air brake systems - typically Class A and Class B commercial vehicles such as tractor-trailers, dump trucks, buses, and heavy straight trucks. In Montana, as federally, you must pass the air brakes knowledge test to have the air brake restriction removed from your CDL; without it, your license carries a restriction prohibiting you from operating air-braked vehicles. The MT CDL Air Brakes case studies are 5 cases and about 3,950 words.
1Pre-Trip Fan-Down Test: Late Warning Buzzer on a Straight Truck
You are doing the pre-trip on a 2018 Freightliner M2 box truck (26,000 lb GVWR, air-braked, dual-circuit, no trailer). At fast idle the dash gauge climbs to 122 psi and the governor cuts out.
778 words, about 4 min2Combination Leak Test with a Faint Gladhand Hiss and Fast Compressor Cycling
Your five-axle tractor-semitrailer sat overnight in cold weather. You build to governor cut-out (123 psi), shut down, and let the system stabilize for a minute.
775 words, about 4 min3Secondary Circuit Failure at Highway Speed on a Downhill
You are driving a 76,000 lb GCW five-axle combination on a two-lane mountain highway at 55 mph. The tractor has separate primary and secondary air gauges; both read 118 psi.
790 words, about 4 min4Brake Fade on a Six-Percent Grade with the Engine Brake Turned Down
You are driving a 78,000 lb GCW five-axle combination down a 6% grade that runs four miles. The posted truck speed is 45 mph.
817 words, about 4 min5Parking Brake Creep on a Grade and a Pushrod at 2 3/8 Inches
You are picking up a loaded tractor-semitrailer in a yard that has a 5% grade. You do the parking brake check: engine running, pressure at 120 psi, you push in the yellow knob, release the service brake, and the rig rolls about four feet before it stops.
790 words, about 4 min