T4 ASE BRAKES (MEDIUM/HEAVY DUTY BRAKES) EXAM 2026/27!!

T4 ASE BRAKES (MEDIUM/HEAVY DUTY BRAKES) EXAM 2026/27!! What are symptoms of defective supply system components? - (ANSWER) Brakes not applying/releasing properly and grabbing or dragging How much of a difference in psi air delivery between axles can cause instability and premature wear? - (ANSWER) 4-psi If all-around braking performance is poor or if the system is not building up enough air pressure, look for signs such as: - (ANSWER) A clogged air compressor filter, slipping belt, air leaks, restricted lines, a defective governor, or even a malfunctioning air compressor What is an air brake governor? - (ANSWER) An air brake governor controls the compressor. It maintains reservoir air pressure between a predetermined min. and max. air pressure. If system pressure is too high suspect a: - (ANSWER) Defective governor or reservoir safety valve. If a governor's cut-out pressure is too high, it can cause: - (ANSWER) Over-pressurization A faulty reservoir safety valve: - (ANSWER) May not be allowing excessive air pressure to be purged from the air tanks When releasing the service brakes and timing the air pressure drop, the loss rate should be less than ___psi/minute for straight trucks and less than ___psi/minute for combination vehicles. - (ANSWER) Less than 2psi/minute for straight trucks and less than 3psi/minute for combination vehicles. When applying the service brakes to at least 90 psi and timing the air pressure drop, the loss rate should be less than ___psi/minute for straight trucks and less than ___psi/minute for combination vehicles. - (ANSWER) Less than 3psi/minute for straight trucks and less than 4psi/minute for combination vehicles. Trucks with air brakes come equipped with pressure gauges mounted on the dash. The gauges will indicate: - (ANSWER) How much air pressure is in the system at any given time When system pressures fall below ___ psi, either a warning light will illuminate, or a buzzer will sound. - (ANSWER) 60 psi Some systems include a _____ _______ gauge, which can inform the driver of specific pressure when the brakes are applied. - (ANSWER) Separate application gauge Dash air pressure gauges operate on the principle of changing an: - (ANSWER) Air brake pressure signal into an electronic voltage signal An element inside an ___ ________ __________ responds to air pressure increase or decrease, the __________ converts that pressure differentiation into a voltage signal, which is displayed in a proportionate reading in the dash gauge. - (ANSWER) Air pressure transducer; transducer To check the transducer and gauge assembly, make sure the air supply value and transducer output voltage are within _______ - (ANSWER) The manufacturer's specifications If the transducer voltage output is not within normal readings, suspect a - (ANSWER) Defective transducer If the transducer voltage output is within normal readings, suspect a - (ANSWER) Defective gauge A defective ________ device will fail to signal the driver of diminished air pressure in the brake system. - (ANSWER) Low-pressure warning device The low-pressure warning indicator is installed on the ______ reservoir, and notifies the operator of ____________. - (ANSWER) Primary reservoir; system air depletion To check the operation of the low-pressure warning indicator, completely ______ the air brake system. - (ANSWER) Depressurize If at 60 psi the low-pressure indicator signals do not operate, check for ______ at the warning device. If the circuit is open, suspect a ________. - (ANSWER) Voltage; defective low-pressure warning device To replace the low-pressure warning device: - (ANSWER) Completely depressurize the air brake system, remove the air lines, and unscrew from the primary reservoir. The ______ reservoir or 'wet tank' is the one closest to the compressor - (ANSWER) Supply reservoir When the brake pedal is depressed, air flows from the primary reservoir, through the primary section of the foot valve, and out to the _______________. - (ANSWER) Rear foundation brakes When the brake pedal is depressed, air flows from the secondary reservoir, through the secondary section of the foot valve, and out to the _______________. - (ANSWER) Front foundation brakes When inspecting the air tank reservoirs, note any damage that may have been cause by ________. - (ANSWER) Road debris When inspecting air reservoir mounting, take into consideration adequate clearance for other components such as __________ and ________. - (ANSWER) Power take off assemblies and brake lines A malfunctioning air compressor can develop air leaks and pass oil into the brake system, which in turn will cause ____________, _______, ________. - (ANSWER) Poor stopping, grabbing, or dragging Although there are many other components in the air brake system, the one that bears the heaviest burden is the _____________. - (ANSWER) Air compressor A ______-cylinder or _______-cylinder compressor is used for most truck applications. However, ______ and ______-cylinder air compressors are available for applications where high air volume is in demand. - (ANSWER) Single-cylinder; two-cylinder; three and four-cylinder Compressors can be _______ cooled, ______ cooled, or both. - (ANSWER) Liquid cooled, air cooled Most compressors utilize oil from the truck's ______ for lubrication - (ANSWER) Engine If an air compressor is self-lubricated, the oil should be checked ______. If the oil is pumped in from the engine compartment, the engine oil should be checked in accordance with the ______________________. - (ANSWER) Daily; engine manufacturer's scheduled maintenance intervals. Power is transferred to the compressor by either an internal gear or an external belt, most commonly called an _____________ belt. - (ANSWER) Accessory drive belt Check engine belts following the manufacturer's recommended intervals for evidence if wear such as _____, ______, ______, ______, and ______. - (ANSWER) Cracking, fraying, missing sections, oil contamination, and incorrect tension Determine engine belt tension at a point ______ between the pulleys by pressing on the belt with moderate thumb pressure. Check belt ______ and compare with manufacturer's recommendations. - (ANSWER) Halfway; deflection When inspecting engine belts, check for hard objects such as ________ or _____ that may become imbedded in the bottom of the belt or in the pulley grooves - (ANSWER) Small stones or sand When replacing the compressor belt, inspect the compressor for ______ and ______ alignment - (ANSWER) Looseness and improper alignment If the engine belt pulleys are severely misaligned, look for improper positioning or the _________, improper fit of the ______ or _______, or incorrect accessory drive components. - (ANSWER) Air compressor; pulley or shaft When replacing engine belts, inspect pulleys for ______, ______, ______, _______, _______, _______, or _______. - (ANSWER) Chips, nicks, cracks, tool marks, bent sidewalls, severe corrosion, or other damage. With the engine running at idle, air pressure should build to 85-100 psi within ______ seconds. - (ANSWER) Forty-five