Hydraulic Brake Systems Overview
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Questions and Answers

Oil from a hydraulic circuit such as the pilot hydraulic system is used to boost the master cylinder's force when the ______ are applied.

brakes

A hydraulic pump is used to supply oil to the boosted ______, via the pilot accumulator.

master cylinder

The service brake pedals control the brake master ______, which send oil under pressure to the brake pistons.

cylinders

This example shows a brake hydraulic system with a boosted master cylinder and two service brake ______.

<p>pedals</p> Signup and view all the answers

Some machines are equipped with a hydraulic boosted brake system to obtain increased ______ force with less effort.

<p>braking</p> Signup and view all the answers

The service brake pedals (1) send oil under pressure to the brake pistons located in the rear ______.

<p>axle</p> Signup and view all the answers

Hydraulic force multiplies the pedal ______ so the operator can brake with less effort.

<p>effort</p> Signup and view all the answers

Caterpillar's hydraulic brake system utilizes the pilot ______ to enhance functionality.

<p>accumulator</p> Signup and view all the answers

The combination valve operates similarly to the charging valve but replaces it with a ______ valve.

<p>priority</p> Signup and view all the answers

The priority valve directs oil flow from the pump to the brake ______ or another hydraulic system.

<p>accumulators</p> Signup and view all the answers

In the combination valve system, the oil flow into the valve is regulated by the ______ valve.

<p>priority</p> Signup and view all the answers

The combination valve is part of the hydraulic brake systems in the Motor ______.

<p>Grader</p> Signup and view all the answers

The pump feeds hydraulic oil into the combination ______.

<p>valve</p> Signup and view all the answers

Another hydraulic system that may receive oil flow from the priority valve is the fan ______.

<p>motor</p> Signup and view all the answers

The relief valve is labeled as ______ in the combination valve diagram.

<p>7</p> Signup and view all the answers

The combination valve ensures that the brake hydraulic system has oil ______ over other systems.

<p>priority</p> Signup and view all the answers

Step 1 is to verify the customer's ______.

<p>concern</p> Signup and view all the answers

Step 2 involves conducting an initial ______.

<p>inspection</p> Signup and view all the answers

In Step 3, you should list possible ______.

<p>causes</p> Signup and view all the answers

The main focus will be on the Investigate and ______ steps.

<p>Isolate</p> Signup and view all the answers

In Step 4, you analyze possible causes to determine the ______ cause.

<p>root</p> Signup and view all the answers

Step 5 involves repairing the ______ cause.

<p>root</p> Signup and view all the answers

Step 6 is to verify the ______ after repairs.

<p>repair</p> Signup and view all the answers

In Step 7, all findings are documented in the ______ Report.

<p>Service</p> Signup and view all the answers

The general procedure to check the service brake pressure involves stopping the engine and placing the transmission direction selector in ______.

<p>NEUTRAL</p> Signup and view all the answers

To release all oil pressure from the brake circuit, you must depress the brake ______ repeatedly.

<p>pedal</p> Signup and view all the answers

A pressure gauge is installed at the rear service brake pressure ______.

<p>port</p> Signup and view all the answers

It is important to allow the hydraulic oil to reach normal operating temperature and normal operating ______.

<p>pressure</p> Signup and view all the answers

If the brake pressure is not in the correct range but the brake accumulator charging valve is functioning correctly, you should replace the brake control ______.

<p>valve</p> Signup and view all the answers

The procedure to test the oil pressure at the front service brakes should be repeated at pressure port ______.

<p>2</p> Signup and view all the answers

Some machines may have a pressure test port near the wheels to check pressure at the inlet to the brake ______.

<p>pistons</p> Signup and view all the answers

The service brake system discussed is a hydraulic ______ brake system.

<p>accumulator</p> Signup and view all the answers

The cut-in/cut-out spool shifts when the accumulator pressure has reached the ______ pressure.

<p>cut-out</p> Signup and view all the answers

The priority valve sends excess oil to other hydraulic ______.

<p>systems</p> Signup and view all the answers

The relief valve limits the ______ pressure in the combination valve circuit.

<p>oil</p> Signup and view all the answers

The orifice removes pump pressure ______.

<p>spikes</p> Signup and view all the answers

The check valve maintains the brake charge ______.

<p>pressure</p> Signup and view all the answers

A pressure switch may be included in the circuit to alert the operator of low ______ pressure.

<p>brake oil</p> Signup and view all the answers

The brake charging ______ valve is responsible for controlling brake pressure.

<p>solenoid</p> Signup and view all the answers

The combination valve provides a link between various hydraulic ______ systems.

<p>brake</p> Signup and view all the answers

To perform the accumulator pressure test, first stop the ______.

<p>engine</p> Signup and view all the answers

The accumulator pressure port is located on the accumulator charging ______.

<p>valve</p> Signup and view all the answers

While performing the test, one must record the highest pressure reading, which is the accumulator cut-______ pressure.

<p>out</p> Signup and view all the answers

After applying service brakes, the pressure should drop, and the lowest pressure is referred to as the cut-______ pressure.

<p>in</p> Signup and view all the answers

If the accumulator pressure readings are not in the correct range, one may need to adjust the accumulator charging ______.

<p>valve</p> Signup and view all the answers

The adjustment screw can be found on the ______ of the accumulator brake pressure setup.

<p>system</p> Signup and view all the answers

It is important to engage the parking ______ before beginning the accumulator pressure test.

<p>brake</p> Signup and view all the answers

After stopping the engine, place the transmission direction selector in the ______ position.

<p>NEUTRAL</p> Signup and view all the answers

Flashcards

Hydraulic Boosted Brake System

A hydraulic system that uses oil pressure to amplify the force applied by the brake pedal, resulting in stronger braking power.

Boosted Master Cylinder

A key component in a boosted brake system that receives oil pressure from the pilot accumulator and transfers it to the brake master cylinders.

Pilot Accumulator

A hydraulic component that stores pressurized oil for the boosted master cylinder, ensuring a quick and powerful brake response.

Service Brake Pedals

Pedals operated by the operator to activate the brake master cylinders, ultimately controlling the brakes.

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Brake Master Cylinders

Devices that convert hydraulic pressure from the boosted master cylinder into mechanical force at the brakes, applying friction to slow down the vehicle.

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Rear Axle

The part of the vehicle that houses the brake assemblies, connecting the brake master cylinders to the wheels.

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Pilot Hydraulic System

A system that uses hydraulic pressure to control the movement of various equipment components, including the brake system.

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Hydraulic Pump

A pump responsible for supplying pressurized oil to the pilot accumulator, ensuring continuous hydraulic pressure for the brakes.

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Combination valve in Motor Graders (MG)

In Motor Grader (MG) applications, the combination valve manages oil flow to both the brake accumulators and other hydraulic systems, prioritizing hydraulic oil flow to the brake system.

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Priority Valve (MG)

A valve that regulates oil flow from the pump to either the brake accumulators or other hydraulic systems in a Motor Grader.

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Brake accumulator (MG)

A component that stores pressurized hydraulic oil for the brake system, ensuring a quick response when the brakes are applied.

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Check valve (MG)

A device that prevents reverse flow of hydraulic oil, ensuring oil flows only in the intended direction.

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Relief valve (MG)

A device that limits pressure in a hydraulic system, preventing damage from over-pressurization.

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Orifice (MG)

A small opening designed to restrict oil flow, creating resistance and controlling the flow rate.

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Pressure switch (MG)

A device that automatically activates when a specific pressure is reached, signaling a system malfunction or overload.

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Cut-in/cut-out spool (MG)

A component that uses hydraulic pressure to generate a force, commonly used in brakes to apply braking force.

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Combination Valve

A component within the hydraulic brake system that directs the flow of hydraulic oil to the appropriate components based on the pressure in the system.

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Cut-in/Cut-out Spool

A valve that allows excess oil pressure to be diverted to other hydraulic systems when the pressure in the accumulator reaches a specific level.

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Brake Accumulator

A component in the hydraulic brake system that acts as a backup source of pressure, providing a quick and powerful brake response.

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Relief Valve

A type of valve that limits the maximum pressure within a hydraulic circuit.

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Orifice

A component placed inside a hydraulic circuit that dampens pressure spikes, ensuring smooth and stable pressure.

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Check Valve

A valve that prevents the flow of hydraulic oil in the reverse direction.

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Pressure Switch

A component that monitors the oil pressure in the brake system and activates an alarm when the pressure falls below a safe level.

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Solenoid Valve

A valve that allows oil to flow through it by opening an electrically controlled solenoid.

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Service Brake Pressure Test

The process of measuring the pressure within the hydraulic brake system to ensure it meets set standards.

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Service Brake Pressure Test Port

A port on the brake system where a pressure gauge can be connected to measure the hydraulic pressure.

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Hydraulic Accumulator Brake System

A system that uses stored hydraulic pressure to provide immediate braking ability, especially helpful when engine power is not available.

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Brake Accumulator Charging Valve

A valve that regulates the flow of hydraulic oil into the accumulator, ensuring proper pressure levels.

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Brake Control Valve

The main component that receives hydraulic pressure and distributes it to the individual brake master cylinders.

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Depress Brake Pedal Repeatedly

To repeatedly depress the brake pedal to release all pressure within the hydraulic system, ensuring a clean reading during testing.

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Normal Operating Temperature

The temperature at which the hydraulic oil in the system should reach during normal operation, allowing for accurate pressure readings.

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Accumulator

A component in a brake system that stores pressurized fluid (typically hydraulic oil) to ensure a quick and powerful response when the brakes are applied.

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Accumulator Charging Valve

A valve connected to the accumulator that controls the pressure of fluid entering the accumulator. It has two key pressure settings: cut-in and cut-out.

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Cut-in Pressure

The pressure at which the accumulator charging valve begins to allow fluid into the accumulator. This is the lowest pressure point before the accumulator starts refilling.

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Cut-out Pressure

The pressure at which the accumulator charging valve stops allowing fluid into the accumulator. This is the maximum pressure the accumulator is allowed to reach.

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Accumulator Pressure (Cut-in/Cut-out) Test

A test used to check the cut-in and cut-out pressures of an accumulator charging valve. It involves recording the highest and lowest pressures during a specific procedure.

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Accumulator Brake Pressure Adjustment

The process of adjusting the pressure settings on the accumulator charging valve to ensure optimal brake performance.

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Adjustment Screw

A screw on the accumulator charging valve that allows you to adjust the pressure settings of the valve by turning it.

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Digital Pressure Indicator Group Tool

A tool designed for measuring and displaying hydraulic pressure. It's helpful for performing the accumulator pressure test.

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Caterpillar 7-Step Diagnostic Process

A systematic approach for identifying, isolating, repairing, and documenting a customer concern. Each step focuses on analyzing and gathering information to direct the following step.

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Step 1: Verify Customer Concern

The initial step in the Caterpillar 7-Step Diagnostic Process involves understanding the nature of the customer's issue by seeking feedback and visually assessing the system.

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Step 2: Conduct Initial Inspection

An important part of the Diagnostic Process, where a thorough examination of the brake system takes place. Signs of leaks, oil levels, and damage to components are inspected.

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Step 3: List Possible Causes

Based on the information gathered during the initial steps, a potential list of contributing factors to the problem is compiled.

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Step 4: Analyze Possible Causes and Determine Root Cause

Analyzing each potential cause from the list and narrowing down the most likely culprit that led to the problem.

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Step 5: Repair Root Cause

Addressing the root cause identified through the diagnostic process by repairing or replacing components.

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Step 6: Verify the Repair

Verifying that the repair successfully resolved the customer's concern by testing the brake system functionality.

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Step 7: Document Concern, Analysis, Repair in Service Report

Recording all the information pertinent to the customer concern, the analysis conducted, and the repairs implemented.

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Study Notes

Global Dealer Learning: Brake Systems Troubleshooting - Hydraulic Brake Systems

  • This module provides information on hydraulic brake system components, operation, testing, and troubleshooting procedures for Caterpillar machines.
  • Safety briefing includes emergency phone numbers, first aid responders, location of exits, fire extinguishers, hazard alerts, evacuation location, storm shelter, and hazardous material information.

Purpose

  • The module covers hydraulic brake system components, operation, testing, and troubleshooting for machines with hydraulic brakes.

Reason

  • Successful completion validates required knowledge, skills, and behaviors for diagnosing and repairing hydraulic brake systems in Caterpillar machines.

Assessment Criteria

  • Knowledge assessment: Closed book, minimum passing score of 80%.
  • Skills assessment: Competent/Not Yet Competent (determined by instructor observation).
  • Instructor observation: Test procedures must be performed correctly.

Learning Outcomes

  • Identify hydraulic brake system components.
  • Explain hydraulic brake system operation.
  • Describe different applications of hydraulic brake systems.
  • Describe hydraulic brake system testing and adjusting procedures.
  • Describe hydraulic brake system troubleshooting procedures.
  • Perform hydraulic brake system testing and adjusting procedures.

Cat 7-Step Diagnostic Process

  • Investigate: Verify customer concern, conduct initial inspection
  • Isolate: List possible causes
  • Analyze: Analyze possible causes, determine root cause
  • Repair: Repair root cause
  • Verify: Verify repair
  • Document: Document concern, analysis, repair in service report

Hydraulic Brake Systems Introduction

  • Introduction to hydraulic brake systems.
  • The Caterpillar 7-Step Diagnostic Process is applied.
  • This module offers basic information about hydraulic brake systems.
  • Advanced courses will build upon this foundation using a structured method.

Hydraulic Brake Systems Overview

  • Components include Hydraulic Master Cylinder, Hydraulic Boosted Master Cylinder, and Hydraulic Brake Accumulator.
  • Master cylinders use oil from a reservoir to apply the brakes. No external oil source is required.
  • Hydraulically boosted master cylinders use an external oil source to reduce the pedal effort.
  • Hydraulic Accumulators store oil under pressure to use when applied for service brakes.

Master Cylinder (CWL)

  • Explains the hydraulic brake system on a compact wheel loader (CWL), without a hydraulic boost.
  • The operator's pedal force is transferred, oil is supplied from the reservoir.
  • The system sends pressurized oil to the brake piston in the brake caliper.

Master Cylinder (BHL)

  • Addresses the hydraulic brake system on a backhoe loader (BHL).
  • Left and right brake pedals are controlled by a linkage to a master cylinder.
  • The left and right brake pedals can be either used together or separately.

Boosted Master Cylinder Review (BHL)

  • Explains hydraulic boosted brake systems on a Backhoe Loader.
  • Use of a hydraulic circuit (like a pilot system) to boost the force of the master cylinder.
  • Operators can achieve greater braking force with less effort using a hydraulic boost.

Boosted Master Cylinder Operation (BHL)

  • Describes the operation of the boosted master cylinder on the backhoe loader.
  • Fluid from the pilot hydraulic system boosts the force applied to the master cylinder.
  • Spring chambers and components are described, along with the associated process.

Boosted Master Cylinder Operation (CWL) – Brakes Released

  • Explains the operation of the boosted master cylinder in a wheel loader with brakes released.
  • Oil flows through the system, and the components remain in the neutral position.

Boosted Master Cylinder Operation (CWL) – Brakes Engaged

  • Describes the boosted master cylinder operation when the brakes are engaged.
  • Servo pistons, plungers, and oil pressure changes are described as the braking system operates.

Boosted Master Cylinder Operation (TH) – Brakes Released

  • Discusses boosted master cylinder operation for a telehandler with brakes released.
  • The hydraulic accumulator is not pressurized and the system is in neutral.

Boosted Master Cylinder Operation (TH) – Brakes Engaged

  • Details the operation when the brakes are engaged, showing the different component interactions using a diagram.
  • The hydraulic pump, the servo piston(s) and accumulators become involved.

Hydraulic Accumulator Brake System Review

  • Identifies components in a hydraulic accumulator brake system on a 972M wheel loader.
  • Describes the role of components in supplying oil for the brake system.
  • Explains how the pedal, valve, and accumulators work together to operate the system.

Brake Charging Valve (Cut-In)

  • Explains the operation of the brake charging valve on a 988G wheel loader in Cut-In mode.
  • The valve controls the oil flow from the accumulators to the hydraulic system.
  • Oil pressure in various parts of the system determine valve actions.

Brake Charging Valve (Cut-Out)

  • Explains the operation of the brake charging valve on a 988G wheel loader in Cut-Out mode.
  • The oil pressure in the accumulators increases, making the valve block oil flow.

Accumulator Charging (LWL)

  • Discusses accumulator charging in large wheel loaders (LWL).
  • Variable hydraulic pumps and pump servo valves control oil flow to accumulators.
  • The control spring, swashplate, and control piston regulate oil flow.

Combination Valve (MG)

  • Describes the combination valve operation in motor grader applications.
  • The priority valve controls oil flow to the brake accumulators or other hydraulic systems (e.g., fan motor), ensuring oil priority to the brakes.
  • The system’s sensors ensure optimal oil pressure.

Combination Valve (MWL)

  • Describes operation in medium wheel loaders.
  • The ECM controls the charging solenoid valve, which steers oil to the accumulators or other systems.
  • Pressure sensors alert the operator of low brake oil pressure.

Systems Testing and Adjusting Overview

  • Overview of testing and adjusting procedures for hydraulic brake systems.
  • Includes descriptions of different tests for troubleshooting.

Operational Checks: Brake Holding Tests

  • Procedures for both service and parking brake holding ability tests.
  • These tests determine whether the brakes are operating correctly.
  • Key steps in the procedure covered, including engine speed, transmission control, and brake operations.

Brake Accumulator Check: Hydraulic Accumulator Brake Systems

  • Explains the general procedure for performing the brake accumulator check.
  • Includes descriptions from a hydraulic schematic

Accumulator Pressure

  • Explains how to check and charge the brake accumulator.
  • Nitrogen usage for proper pressure and stability is described, along with steps to perform this process.

Service Brk Pres Test: Master Cyl Brake Sys

  • Describes the general procedure to check service brake pressure on machines with master cylinders.
  • Gauge installation and pressure readings are important parts to understanding this testing process.

Service Brk Pres: Hyd Accum Brake System

  • Describes the general procedure to check service brake pressure on machines with hydraulic accumulator brake systems.
  • Steps for testing the pressure and checking for defects in the system are described.

Accum Pressure (Cut-in/Cut-Out) Test

  • Explains the general procedure for the accumulator pressure cut-in/cut-out test.
  • The process involves checking the highest and lowest pressures, with the goal of finding any irregularities.
  • Includes instructions for using appropriate gauges.

Accumulator Brake Pressure Adjustment

  • Explains how to adjust the accumulator pressure.
  • Includes using a plug and an adjustment screw.

Parking Brake Pressure

  • Explains the general procedure to adjust the parking brake pressure.
  • Includes steps for engine start-up and adjusting the pressure to within manufacturer specifications.

System Troubleshooting Overview

  • Overview of common troubleshooting processes for hydraulic brake systems.
  • It highlights the use of troubleshooting charts to analyze possible causes.

Caterpillar 7-Step Diagnostic Process

  • Detailed steps to follow for investigating, isolating, repairing, and documenting a brake issue.
  • Describes each step in detail.

Initial Inspection

  • Explains the steps to perform a thorough initial inspection of the hydraulic brake system to check for leaks, damage and any problems which could have contributed to the problem.
  • Includes diagrams.

Symptom Troubleshooting

  • Detailed chart helps establish troubleshooting steps for various scenarios.
  • The intent of the troubleshooting chart is to help technicians establish probable causes.

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Description

This quiz focuses on the hydraulics involved in brake systems, particularly the pilot hydraulic system and its components. Test your knowledge on how hydraulic force boosts the master cylinder and the functionality of various valves in managing brake pressure. Perfect for those studying automotive technology or engineering.

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