Mecanica Automotriz

Introduction to Brake Systems – Study Guide
©2004 Melior, Inc.
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Introduction
Everybody knows that when you press your foot on the brake pedal the vehicle is supposed to stop. But
how does the pressure from your foot get to the wheels with enough force to stop a heavy vehicle? In the
following sections, wewill study the systems and components required to allow brakes to work effectively.

Course Objectives
Upon completion of this course, technicians should understand and be able to apply their knowledge of:
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Brake functions and components
Split hydraulic systems
Master cylinder operations
Balance control systems
Power brake booster systems
Disc brakeoperation
Micrometer reading
Drum brake operation
Brake fluids
Brake bleeding operations
Brake lines and hoses
Basic diagnosis

Using the Job Sheets
As you proceed through the online module, on some pages you will find links that will open a window with
a printable procedure or job sheet containing hands-on lab activities based on the NATEF standards
related to the content you arestudying. When you come upon a procedure or job sheet link, click on it
and print the job sheet for completion in the shop. See your instructor for guidance in completing the job
sheets. Some jobs sheets will require supplemental materials such as a vehicle service manual,
equipment manual, or other references.

Brake System Functions
Automotive brakes are designed to slow and stop a vehicle bytransforming kinetic (motion) energy into
heat energy. As the brake linings contact the drums/rotors they create friction which produces the heat
energy. The intensity of the heat is proportional to the vehicle speed, the weight of the vehicle, and the
quickness of the stop. Faster speeds, heavier vehicles, and quicker stops equal more heat.
Automotive brake systems can be broken down
intoseveral different sub-systems (fig. 1):
• Apply system
• Boost system
• Hydraulic system
• Wheel brakes
• Balance control system
• Warning system

(fig. 1) Base Brake Systems

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©2004 Melior, Inc.

Introduction to Brake Systems – Study Guide_____________________________________________________________________________________________
Base brake components are the parts of the
brake system commonly found on all vehicles.
The term ''base brakes'' does not include either
Antilock or Traction Control systems. Base
brake components include:
• Brake pedal and linkage
• Power assist system
• Master cylinder, hoses and lines
• Brake rotors and pads
• Brake drums and shoes
• Balance controls(proportioning valve
and metering valve), if equipped
• Brake pressure and other warning
systems
• Parking brake pedal and linkage

(fig. 2) Base Brake Components

Split Hydraulic Systems
A partial loss of brake pressure makes it difficult or even impossible to apply the brakes. Therefore,
federal law requires that all vehicles have two separate and independent hydraulic systems. In this way,the failure of one system will not result in a complete brake loss even though braking will still be severely
reduced.
The two split systems used almost exclusively are:
• Diagonally split – used on most front wheel drive vehicles
• Front/rear split – used on most rear wheel drive vehicles
On a diagonally-split system (fig. 3), the left-front and right-rear brakes (LF/RR) are connected toone
channel of the master cylinder while the right-front and left-rear brakes (RF/LR) are connected to the
other channel of the master cylinder. This system is typically installed on front wheel drive vehicles
because they have a front-heavy weight distribution and approximately 70% of the braking occurs at the
front brakes. As such, if one part of a diagonal system failed, the overall braking...