Parking Brake System Components

Global Dealer Learning - Brake Systems Troubleshooting

• This module provides information on air brake system components, operation, testing, and troubleshooting procedures for various types of machines equipped with air brakes.

Safety Briefing

• Emergency Phone Numbers
• First Aid Responders
• Location of Exits
• Location of Fire Extinguishers
• Room Alerts or Hazards
• Designated Location for Evacuation
• Storm Shelter
• Hazardous Materials

Purpose

• This module covers air brake system components, operation, testing, and troubleshooting procedures for machines with air brake systems.
• Explains the purpose of the module.

Reason

• Successful completion validates the knowledge, skills, and behaviors required for diagnosing and repairing air brake systems in Cat machines.
• Explains the reason for this module.

Assessment Criteria

• Knowledge Assessment: closed book, minimum passing score 80%.
• Skills Assessment: competent/not yet competent.
• Instructor Observation: test procedures performed correctly.
• Explains the criteria for assessment.

Learning Outcomes

• Identify air brake system components.
• Explain air brake system operation.
• Describe different air brake system applications and adjusting procedures.
• Describe air brake system troubleshooting procedures.
• Perform air brake system testing and adjusting procedures.
• Explains the learning outcomes of the module in further detail, regarding air brake component identification, operation explanation, applications description and different types of procedures for testing, and adjusting the air brakes systems.

Air Brake Systems Troubleshooting Intro

• Cat 7-Step Diagnostic Process is introduced for air brake systems troubleshooting.
• The steps include Investigating, Isolating, Listing Possible Causes, Analyzing, Repairing, Verifying and Documenting
• Explains the introduction to air brake systems troubleshooting
• Provides a 7-step diagnostic approach to problem-solving

Air Brake Systems Overview

• Overview of all air brake systems and air over hydraulic systems used in Cat equipment.
• Explains the operation of all air brake systems used currently on Cat machines.
• Includes the various components and their functions in each system.

Service Brake Circuit (MG)

• Identify the service brake circuit on a Motor Grader (MG).
• The air brake system on a motor grader uses air pressure for activating and engaging the service brakes (both sides).
• Air flows from the air reservoir to the service brake control valve through multiple disc brakes.

Parking Brake Circuit (MG)

• Identify the parking brake circuit on a Motor Grader (MG).
• The parking brake on an MG system is a multi-disc assembly connected to the transmission, keeping the transmission output shaft from turning.
• Air flows through the service brake control valve to the parking brake control valve, to block air flow to the brake actuator, thereby engaging the parking brake.

Service Brake Circuit (WTS)

• Identify the service brake circuit on a Wheel-Tractor Scraper (WTS)
• This system's service brakes and parking brakes are controlled by independent circuits with dual brake chambers for engagement, one for service, and one for parking brakes.

Parking Brake Circuit (WTS)

• Identify the parking brake circuit on a Wheel-Tractor Scraper (WTS).
• The parking brake in this system utilizes a multi-disc assembly that prevents the transmission output shaft from turning when engaged; this engagement happens when a control lever is set to a parking brake ENGAGED position.,
• When the transmission control lever is not in the parking brake engaged position, air flows, engaging the service brakes.

Service Brake Circuit (AT)

• Identify the service brake circuit on an Articulated Truck
• In many articulated trucks, front brakes are air over hydraulic and rear brakes and parking brakes are air pressure activated.
• A primary difference between the service brakes and the parking brakes is that the parking brakes are engaged by air pressure, a hydraulic brake actuator engages the front brakes, while a dual brake chamber engages both the rear service brakes and parking brakes.

Parking Brake Circuit (AT)

• Identify the parking brake circuit on an Articulated Truck.
• Air flow in this circuit is controlled by a parking brake control valve; when activated it blocks the air flowing to the brake actuators. The spring force in the brake actuators engages parking brakes,

Service Brake Circuit (MWL)

• Identify the service brake circuit on a Medium Wheel Loader (MWL).
• This system employs air over hydraulic brakes to engage the front and rear service brakes by using air pressure to actuate a hydraulic piston and engage the service brakes.
• When the left and right pedals are depressed, air pressure flows to the hydraulic brake actuators engaging both brakes.

Parking Brake Circuit (MWL)

• Identify the parking brake circuit on a Medium Wheel Loader (MWL).
• Air from the air reservoir operates the parking brake control valve to block air; spring force in the brake actuator engages the brakes.
• When the lever is deactivated, air is directed through various components engaging the parking brakes' release

Service Brake Air Circuit (OHT)

• Identify the service brake air circuit on an Off-Highway Truck (OHT)
• The service brakes and parking brakes used in off-highway trucks use an air over hydraulic brake system; these trucks' multiple disc brakes perform functions for service and parking.
• Air flows from the reservoir to the service brake control valve, relay valve to the double check valve preventing air from entering the retard valve.

Service Brake Hydraulic Circuit (OHT)

• Identify the service brake hydraulic circuit on an Off-Highway Truck (OHT).
• Compressed air pressure operates a piston, which engages oil in the brake cylinder, engaging the service brakes.
• The makeup oil tank provides a continuous supply of oil for the brake cylinders.

Parking Brake Circuit (OHT)

• Identify the parking brake circuit in an Off-Highway Truck (OHT).
• In the OHT's parking brake circuit, the release valve uses air pressure to activate a hydraulic valve spool, directing oil pressure that releases the parking brakes.
• Engagement is activated when the parking brake switch is ENGAGED position, blocking air flow, engaging the brakes.

System Testing and Adjusting Overview

• Overview of brake system testing and adjusting procedures, including locating pressure test locations, describing test procedures, and describing adjusting procedures.
• Provides information on common air brake system pressure tests, which are routinely performed and/or required during a TA2 inspection
• Notes that TA2 inspection forms are in the service information system or on Caterpillar's online platform.

Brake Holding Ability Test

• Procedure for performing the service brake and parking brake holding ability tests.
• These tests determine whether the service and parking brakes operate within specifications, with additional inspection and/or testing required if the machine moves during the tests.
• Indicates the steps for carrying out service and parking brake holding ability tests in machines. This includes starting the engine, adjusting the transmission and applying/releasing the brakes.

Leak Check

• Procedure for performing the air leakage checks to locate leaks.
• The procedure involves starting the engine to allow air pressure to reach the maximum pressure.
• Leaks are diagnosed by applying soapy water to connections or components that have potential leaks.

Air Pressure Gauge Test

• Explaining the general procedure for conducting air pressure gauge tests.
• Describes the testing procedure for verifying the accuracy of air pressure gauges by comparing to a test gauge, including installation of gauges at the appropriate ports and recording pressure differences.
• The test utilizes a 198-4240 Digital Pressure Indicator.

Air Compressor Governor Test

• Explains the general procedure for performing the air compressor governor test
• Describes the test procedure for testing governor operation and recording cut-in and cut-out air pressure.

Air Compressor Governor Adjustment

• Describes the procedure for adjusting the air compressor governor to ensure that cut in and cut out pressures are within specifications.

Low Brake Air Pressure Switch Test

• Explains the general procedure for performing the low brake air pressure switch test.
• Provides specific steps for testing, checking connections, and adjusting if necessary.
• Records the test results.

System Protection Valve Test (AT)

• Explains the general procedure for the system protection valve test on Articulated Trucks, involving steps for testing the valve's functionality and checking for leaks
• Explains how to operate the air brake system to diagnose and test the valve

Parking Brake Air Pressure Test

• Explains the general procedure for testing the parking brake air pressure.
• Covers the procedure for starting the engine, setting the parking brake control valve, and recording pressure readings

Service Brake Air Pressure and Oil Pressure Test

• Explains the general procedure for the service brake air pressure and oil pressure test.
• Describes the proper procedures and steps to take and the various parts and equipment needed to conduct the test

Hydraulic Cylinder Stroke Test

• Explains the general procedure for performing the hydraulic cylinder stroke test used in air over hydraulic brake systems, including how to use the 1U-9360 Displacement Gauge to check the stroke.

Slack Adjuster Test

• Explains the general procedure for performing the slack adjuster test in an air over hydraulic brake system, indicating how to test the slack adjuster and what to do if the test reveals a problem.

Parking Brake Oil Pressure Test

• Provides a procedure for checking the parking brake oil pressure in air over hydraulic brake systems.
• Includes steps on installing pressure gauges, starting the engine, and operating the system.

System Troubleshooting Overview

• Gives an overview of system troubleshooting, including a diagnostic strategy for isolating the root and cause of a fault
• This section identifies component inspections and test types for troubleshooting air brake system problems, with examples.
• Indicates possible causes based on identified symptoms, with guidance from different troubleshooting charts/manuals.

Cat 7-Step Diagnostic Process

• Explains how to use the Caterpillar 7-Step Diagnostic Process to investigate and isolate steps in air brake system troubleshooting, including visual inspections for external issues and leaks.
• Outlines steps involving engine start-up, pressure checking, and evaluating system operation.

Initial Inspection

• Provides a general outline of performing an external inspection of the air brake system, covering various components such as the air compressor, governor, brake lines, fittings, air reservoirs, and the brake control valve..

Symptom Troubleshooting

• Reviews troubleshooting charts provided in the Instructor Materials and Activity Workbook.
• Describes the purpose to teach diagnostic principles rather than all troubleshooting details (with current service information for full details).
• Explains how to use symptom troubleshooting to create a list of possible causes based on identified symptoms, with the help of the testing and adjusting manuals.