Parking Brake System Components

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Questions and Answers

What role does the ECM play when the parking brake knob is pushed in?

The ECM energizes the solenoid valves, allowing air to flow into the parking brake chamber.

What happens to the parking brake springs when the air fills the parking brake chamber?

The parking brake springs are compressed, which retracts the actuator rods.

Identify the components that allow air to flow from reservoirs to the parking brake chamber.

Air flows through the double check valves and the quick release and holding valves.

What is the function of the quick release valve in the parking brake circuit?

The quick release valve facilitates rapid air exhaust from the brake chamber. Signup and view all the answers

Explain the significance of the air reservoirs in the parking brake system.

Air reservoirs store compressed air needed for brake system operation. Signup and view all the answers

What is the relationship between the parking brake control valve and the parking brake system?

The parking brake control valve regulates the flow of air to the parking brake chamber. Signup and view all the answers

Describe the effect on brake performance if the air dryer fails.

A failure in the air dryer can lead to moisture in the air system, affecting brake reliability. Signup and view all the answers

What does the term 'relay valve' refer to in the context of the braking system?

The relay valve helps to enhance the response and efficiency of the braking system. Signup and view all the answers

What is the role of the slack adjuster in a brake system?

The slack adjuster compensates for brake disc wear by allowing oil flow and maintaining slight pressure on the brake piston. Signup and view all the answers

How does the makeup oil tank support the braking system?

The makeup oil tank supplies oil for the brake cylinders, ensuring a constant supply for optimal operation. Signup and view all the answers

Describe the function of the parking brake release valve in the OHT parking brake circuit.

The parking brake release valve uses air pressure to move a hydraulic valve spool, directing oil pressure to release the parking brakes. Signup and view all the answers

Explain the role of the parking brake air reservoir in the system.

The parking brake air reservoir stores air that is used to actuate the parking brake release valve. Signup and view all the answers

What function does the parking brake switch serve?

The parking brake switch indicates the status of the parking brake, ensuring that the driver is aware when the brake is engaged or released. Signup and view all the answers

Identify the primary source of oil for the brake cylinders.

The primary source of oil for the brake cylinders is the makeup oil tank. Signup and view all the answers

What happens to the oil under low pressure in the slack adjuster?

Under low pressure, a small volume of oil remains between the slack adjuster and the brake piston. Signup and view all the answers

How does the parking brake release pump contribute to the parking brake system?

The parking brake release pump supplies oil flow to the parking brake release valve, facilitating brake disengagement. Signup and view all the answers

What is the first step to conduct the parking brake holding ability test?

Start the engine and allow air pressure to reach the normal operating range. Signup and view all the answers

What position must the transmission control be in during the parking brake holding ability test?

The transmission control must be in the MANUAL position. Signup and view all the answers

What should be done to the machine after raising the implement during the parking brake test?

Engage the parking brake. Signup and view all the answers

What action is required if the machine is parked on a slope during the parking brake test?

The parking brake should be tested while the machine is parked on a slope. Signup and view all the answers

What engine speed should be set after engaging the parking brake in the test?

Increase the engine speed to high idle. Signup and view all the answers

What should the operator do after the machine is successfully tested for parking brake holding ability?

Reduce the engine speed to low idle and move the transmission control to the NEUTRAL position. Signup and view all the answers

What is the outcome if the machine moves during the parking brake test?

The parking brake fails the holding ability test. Signup and view all the answers

What safety considerations should be taken before performing the parking brake holding ability test?

Carry out all necessary safety checks, precautions, and procedures. Signup and view all the answers

What is the purpose of the Caterpillar 7-Step Diagnostic Process in brake system service?

The process aims to systematically investigate, isolate, repair, and document customer concerns regarding brake system issues. Signup and view all the answers

What is the first step to take when a customer reports erratic brake operation?

The first step is to conduct a visual inspection to identify symptoms that may indicate issues within the brake system. Signup and view all the answers

During the visual inspection, what specific signs should be looked for?

Look for signs of external leaks and any damage to the brake system components. Signup and view all the answers

What follows the visual inspection in the diagnostic process?

After the visual inspection, develop a list of possible causes based on the findings, such as air or oil restrictions or leaks. Signup and view all the answers

Why is it important to perform tests to determine air pressure in the brake system?

Testing air pressure is critical to identifying the root cause and ensuring that the air brake system functions effectively. Signup and view all the answers

What should be maintained in the air brake system while repairing the identified issue?

Proper air pressure must be maintained in the air brake system to ensure correct functionality during repairs. Signup and view all the answers

What is the final verification step after completing repairs on the brake system?

Verify the repairs by checking that the air pressure is correct and ensuring there are no external leaks. Signup and view all the answers

How does the Caterpillar 7-Step Diagnostic Process benefit technicians?

It provides a clear and organized method for diagnosing and resolving brake system issues effectively. Signup and view all the answers

What is the primary purpose of the air pressure gauge test?

To verify the accuracy of the air pressure gauges by comparing the air pressure value to a test gauge. Signup and view all the answers

What is the first step in the general procedure for the air pressure gauge test?

Release the air pressure from the air reservoir by opening the drain valves. Signup and view all the answers

Which tool is recommended for performing the air pressure gauge test?

The 198-4240 Digital Pressure Indicator Group. Signup and view all the answers

After starting the engine, what should be done once the air pressure reaches maximum pressure?

Record the air pressure on all gauges and note the difference between the cab air gauge pressure and the test pressure gauges. Signup and view all the answers

What should be done if the difference in pressure readings is not within specification?

The cab air pressure gauge may require replacement. Signup and view all the answers

How many gauges are involved in the air pressure gauge test procedure?

At least two gauges are involved: the cab air gauge and the test pressure gauges. Signup and view all the answers

What should be installed at each drain valve port and cab air gauge port during the test?

A pressure gauge should be installed at each location. Signup and view all the answers

Why is it important to note the difference in pressure readings during the test?

Noting the difference helps determine if the cab air gauge is functioning correctly. Signup and view all the answers

What is the primary function of the brake actuators in the service brake circuit?

The brake actuators engage the service brakes by utilizing air pressure. Signup and view all the answers

Describe how air pressure is utilized in the service brake circuit.

Air pressure flows from the air reservoir to the service brake control valve, actuating the brakes when the pedal is depressed. Signup and view all the answers

What role does the service brake control valve play in the braking system?

The service brake control valve directs air to the brake actuators when the brake pedal is pressed. Signup and view all the answers

How does the parking brake maintain the transmission output shaft's position?

The parking brake, when engaged, prevents the transmission output shaft from turning. Signup and view all the answers

What are the consequences of air reservoir failure in the brake system?

Failure of the air reservoir would result in loss of air pressure needed to engage the brakes effectively. Signup and view all the answers

Identify the circuit responsible for activating the service brakes.

The service brake circuit is responsible for activating the service brakes. Signup and view all the answers

What mechanism applies the brakes in a Motor Grader (MG) when using the pneumatic air brake system?

The multiple disc assembly applies the brakes by utilizing compressed air. Signup and view all the answers

How is the parking brake control valve related to the functionality of the parking brake?

The parking brake control valve regulates the air supply that engages the parking brake mechanism. Signup and view all the answers

Study Notes

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.

Studying That Suits You

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Description

This quiz explores the essential components and functions of the parking brake system. It addresses topics such as the role of the ECM, air reservoirs, and various valves involved. Enhance your understanding of the braking mechanism and its significance in automotive systems.