ASE H4 Brakes (Transit Bus) case studies
ASE H4 Brakes (Transit Bus) · Put your knowledge to work in context.
ASE H4, Brakes (Transit Bus), is one of the specialty credentials in the ASE transit bus certification series. It certifies that a technician can inspect, diagnose, service, and repair the brake systems found on heavy-duty transit coaches: air brake circuits and valves, compressors and air dryers, hydraulic systems on buses so equipped, parking and mechanical brakes, ABS and electronic brake controls, plus the diagnostic and adjustment work that ties them together. The ASE H4 Brakes (Transit Bus) case studies are 5 cases and about 2,364 words.
1Low Pressure Buildup After Overnight Cold Soak
A 40-foot transit bus with a Cummins ISL and a twin-cylinder water-cooled compressor reports a low-pressure warning at first start on a 15°F morning. The dash gauge shows 60 psi after 4 minutes of fast idle; the governor cuts out at 125 psi after another 6 minutes, but the compressor cycles back in within 90 seconds and the wet tank drains show a teaspoon of milky emulsion each morning.
535 words, about 3 min2Brake Drag and Heat After a Reline
A technician relined the rear brakes on a low-floor transit bus with Bendix ADB22X air disc brakes. After the road test, the left rear rotor measures 480°F while the right rear measures 210°F.
481 words, about 2 min3ABS Lamp On After Wheel Speed Sensor Replacement
A technician replaced a right front wheel speed sensor on a transit bus with a Bendix ABS-6 system after a wheel seal leak contaminated the original sensor. The ABS lamp is still on after the repair, and the blink code indicates a right front sensor fault.
485 words, about 2 min4Spring Brake Won't Hold on a Grade
A transit bus fails its annual inspection because the parking brake will not hold the vehicle on a 20% grade. The bus has spring brakes on the rear axle and a driveline parking brake is not fitted.
459 words, about 2 min5Hydraulic Brake Pedal Fade on a Cutaway Bus
A cutaway transit bus with a hydro-boost hydraulic brake system has a low, spongy pedal that fades toward the floor when held at a stoplight. The reservoir is at the full mark and the fluid is dark.
404 words, about 2 min