ASE T4 Brakes (Medium/Heavy Truck) study guide
ASE T4 Brakes (Medium/Heavy Truck) · Work through your exam, one topic at a time.
T4 is one of the T Series (T1–T8) Medium-Heavy Truck Certification Tests offered by the National Institute for Automotive Service Excellence. ASE describes the T Series as designed "to identify and recognize those Medium and Heavy Truck Technicians who can demonstrate knowledge of the skills necessary to diagnose, service, and repair different systems of Class 4 through Class 8 trucks and tractors." T4 is the brakes test in that series, and it is aimed at working technicians who service medium- and heavy-duty trucks and tractors rather than light vehicles - the light-truck brake content lives in the A Series instead. The ASE T4 Brakes (Medium/Heavy Truck) study guide has 4 sections and about 2,135 words.
01Air Supply and Service System Components
The supply system makes and stores air; the service system delivers it on demand. The engine-driven compressor pumps through a discharge line to the air dryer, then into the wet tank , and through a one-way check valve into the dry tank(s) that feed the foot valve.
337 words, about 2 min02Air Brake System: Foundation Brakes, ABS and Automatic Traction Control
The service chamber pushrod pushes the slack adjuster , which rotates the S-cam ; the cam spreads the shoes against the drum. Applied torque depends on chamber size, slack adjuster length, and drum diameter.
724 words, about 4 min03Hydraulic Brake System Diagnosis and Repair
The master cylinder creates pressure; the compensating port lets fluid return as it expands with heat. A combination valve may package a metering valve (delays front apply on some designs), a proportioning valve (limits rear pressure), and a pressure differential switch that lights the warning lamp if a circuit fails.
351 words, about 2 min04Parking Brake Systems, Wheel Bearings, Seals and Related Components
Most heavy trucks use spring brake chambers : a powerful spring applies the brake, and air pressure compresses it to release. Loss of air therefore applies the parking brake - the fail-safe principle.
723 words, about 4 min