Block C – Air Systems And Brakes

Trends

There is an increasing use of disc brakes due to ease of service and improved materials and design.

There are also new safety technology controls such as roll over stability control, vehicle on board radar (VORAD) and collision warning systems that are being introduced in the industry.

Related Components (including, but not limited to)

Air systems: air dryer, air starters, compressors, relay valves, air tanks, relief valves, check valves, air lines, governors, pressure switches, gauges, drain valves (automatic or manual), quick release valves, low pressure indicator, dash control valves, trailer supply lines, glad hands.

Brake systems: brake chambers, slack adjusters (automatic and manual), rotors, calipers, S-cams, springs, pins, bushings, rollers, master cylinders, brake cylinders, hydraulic power boosters, pressure differential valves, metering valves, proportioning valves, foot valves, brake proportioning valves, trailer application valves, relay valves, quick release valves, ratio valves, inversion valves, bobtail proportioning valves, spring brake control valves, tractor protection valves, check valves, stop lamp switches, air pressure gauges, clevis pins, power assisted systems, brake drums, brake shoes, brake spiders, ECUs, sensors.

Tools and Equipment

ASee Appendix A.

Task 12 Services, diagnoses and repairs air systems.

Context

Truck and transport mechanics must service, diagnose and repair air systems to ensure proper function and reduce down time.

Air systems provide compressed air to control and operate vehicle systems and components such as braking, fan hubs and ride height, and accessories such as seats, wipers and fifth-wheel slide cylinders.

Required Knowledge

• K 1 air system design and function
• K 2 air system components such as compressors, governors, valves and low air warning systems
• K 3 common faults such as ruptured and chafed hoses, sticking valves, faulty compressor and system not building air pressure
• K 4 air system specifications
• K 5 schematics and troubleshooting trees
• K 6 specialty air system tools such as air pressure gauges and their applications and operation
• K 7 jurisdictional requirements for road testing
• K 8 hazards of servicing air systems

Sub-task - C-12.01 Services air systems.

Key Competencies

• C-12.01.01 perform sensory inspections of air systems to identify worn, damaged or defective components such as air lines, air dryers, governors, compressors, brake chambers (pots) and air tanks
• C-12.01.02 measure air pressures to determine if they meet manufacturers’ specifications and jurisdictional requirements
• C-12.01.03 release stored energy such as air pressure by opening air valves and fanning down brakes
• C-12.01.04 remove and replace air dryer filters according manufacturers’ specifications and employer maintenance schedule
• C-12.01.05 recycle and/or dispose of consumable air dryer filters and brake chambers according to jurisdictional regulations
• C-12.01.06 record service information and inspection findings according to manufacturers’ requirements for warranty, and for future reference and tracking
• C-12.01.07 adjust governing air pressures to meet manufacturers’ specifications

Sub-task - C-12.02 Diagnoses air systems.

Key Competencies

• C-12.02.01 obtain details of symptoms associated with complaint to establish a starting point for diagnostics
• C-12.02.02 perform audible and visual inspections of components such brake chambers, air lines, tanks, valves, air gauges and air dryers to confirm complaint and establish a preliminary diagnosis
• C-12.02.03 perform diagnostic procedure by following troubleshooting tree or schematic supplied by manufacturer to determine failure
• C-12.02.04 perform specialized testing procedures such as pressure tests, timed tests and leakdown to assess components for wear, damage or defects by using diagnostic tools such as soap and water, gauges and hand tools
• C-12.02.05 compare test results to manufacturers’ specifications or expected values to verify diagnosis
• C-12.02.06 record test results and inspection findings according to manufacturers’ requirements for warranty, and for future reference and tracking

Sub-task - C-12.03 Repairs air systems.

Key Competencies

• C-12.03.01 remove and replace worn, damaged or faulty components such as air lines, relay valves, brake chambers, modulating valves, governors, compressors and air dryer filters
• C-12.03.02 rebuild components such as air compressors, brake chambers, air dryers and purge valves by replacing worn parts, according to manufacturers’ specifications
• C-12.03.03 repair components such as air starters, compressors, air dryers and driver warning systems by replacing parts causing the failure, according to manufacturers’ specifications
• C-12.03.04 perform adjustment procedures such as air governors and ride height valves (leveling valves) to ensure proper operation of air system
• C-12.03.05 verify repair by using methods such as road testing, load testing and sensory observations
• C-12.03.06 document that repairs and verifications have been performed for warranty, liability, future reference and tracking

Task 13 Services, diagnoses and repairs brake systems.

Context

Truck and transport mechanics must service, diagnose and repair brake systems to ensure proper function and reduce down time.

Brake systems slow or stop the vehicle in a safe and controlled manner by using air, hydraulics or cable in conjunction with electronic controls.

Required Knowledge

• K 1 types of brake systems such as air, hydraulic and emergency (parking) brake
• K 2 operating principles of anti-lock braking system (ABS), roll stability protection and traction control
• K 3 components of air brakes such as brake chambers, slack adjusters (automatic and manual), rotors, S-cams, pins and bushings
• K 4 hydraulic brake components such as master cylinders, wheel cylinders and brake proportioning valves
• K 5 emergency (parking) brake components such as drums and shoes
• K 6 ABS components such as wiring, ECMs, modulating valves and sensors
• K 7 types of brake shoes, pads and linings
• K 8 brake system operation
• K 9 common faults such as broken brake chamber springs, leaking diaphragms and loose calipers
• K 10 traction control and braking systems
• K 11 warning systems
• K 12 troubleshooting trees and schematics
• K 13 jurisdictional requirements for road testing and road worthiness
• K 14 hazards associated with brake systems

Sub-task - C-13.01 Services brake systems.

Key Competencies

• C-13.01.01 clean brake system components such as ABS components, drums, shoes, pads, rotors, cams and slack adjustors
• C-13.01.02 perform sensory inspections of brake components to identify leaks or worn, damaged or defective components such master cylinders, ABS modules, worn shoes and drums, broken springs, slack adjustors and cams
• C-13.01.03 measure brake system components such as slack adjustors, brake lining and rotors for brake stroke measurements, drum wear and thicknesses to determine if they meet manufacturers’ specifications and jurisdictional requirements
• C-13.01.04 check fluid levels in master cylinders to determine if they meet manufacturers’ specifications
• C-13.01.05 release stored energy in components such as brake chamber springs
• C-13.01.06 remove and replace consumable components such as brake linings and fluids according manufacturers’ specifications
• C-13.01.07 recycle and/or dispose of consumable components according to jurisdictional regulations
• C-13.01.08 adjust brakes and lubricate components according to manufacturers’ specifications
• C-13.01.09 recalibrate sensors for ABS according to manufacturers’ specifications
• C-13.01.10 bleed hydraulic brakes according to manufacturers’ specifications
• C-13.01.11 identify types of power assisted hydraulic brakes
• C-13.01.12 record service information and inspection findings according to manufacturers’ requirements for warranty, and for future reference and tracking

Sub-task - C-13.02 Diagnoses brake systems.

Key Competencies

• C-13.02.01 obtain details of symptoms associated with complaint to establish a starting point for diagnostics
• C-13.02.02 perform sensory inspections such as braking performance, ABS lights, oil and air leaks to confirm complaint and establish a preliminary diagnosis
• C-13.02.03 measure brake system components such as slack adjustors, brake lining and rotors for brake stroke measurements, drum wear and thicknesses
• C-13.02.04 perform diagnostic procedure by following troubleshooting tree or schematic supplied by manufacturer to determine failure
• C-13.02.05 perform specialized testing procedures such as leakdown test, performance test and road test to assess components for wear, damage or defects using ABS and hydraulic diagnostic equipment
• C-13.02.06 interpret schematics and compare test results to manufacturers’ specifications or expected values to verify diagnosis
• C-13.02.07 perform failure analysis to determine root cause of failure
• C-13.02.08 record test results and inspection findings according to manufacturers’ requirements for warranty, and for future reference and tracking

Sub-task - C-13.03 Repairs brake systems.

Key Competencies

• C-13.03.01 remove and replace worn, damaged or faulty brake components such as slack adjusters, brake chambers, cables, wheel cylinders and master cylinders
• C-13.03.02 rebuild and repair components such as master cylinders, calipers, air lines, hydraulic lines and ABS components according to manufacturers’ specifications
• C-13.03.03 perform adjustment procedures by adjusting components such as brakes, ABS sensors and parking brakes to ensure proper operation and according to manufacturers’ specifications
• C-13.03.04 verify repair by using methods such as road testing, load testing and sensory observations
• C-13.03.05 document that repairs and verifications have been performed for warranty, liability, future reference and tracking