Orientation to Hydraulic Brake Systems. Module One Chapter 4

Copy of objective sheet Copy of key terms Copy of ASE style review questions Copy of task sheet and PPE Notebook Pen/Pencil

Materials

For students to understand the basic theory of operation, components and maintenance of today's hydraulic brake systems.

Goals

After this lesson you should be able to: Explain the operation of a hydraulic brake

system and the fluids used in the system. Describe the operation of drum brakes, disc

brakes and dual brakes in a hydraulic braking system.

Describe the operation and maintenance of : Wheel Cylinders, Calipers, Master Cylinder, Combination Valve.

Objective

A Hydraulic Brake System is a system utilizing the properties of fluids under pressure to activate the brakes to create friction to stop a moving vehicle.

Typical hydraulic brake systems use DOT 3 or 4 fluid but some systems use silicone based DOT 5 fluid.

Be careful “not” to mix Dot3/4 with DOT5.

Hydraulics

Avoid spilling brake fluid on the paint . Brake fluid will fade or remove the paint!

As you depress the brake peddle you transmit the energy from your leg onto the brake peddle lever. This force is multiplied by the length and lever position of the peddle to the master cylinder.

System operation

The movement of the brake peddle creates flow from the master cylinder through the combination valve and into the larger brake actuators again, multiplying the braking force.

System Operation

Most vehicles today use master cylinders that have the reservoir built onto the master cylinder with two sumps to store the brake fluid.

They are duel system type master cylinders that create flow to the larger diameter slave cylinders like your wheel cylinders and caliper assemblies.

Master Cylinder

The combination valve supports three functions in the brake system.

Warning/Safety Metering (front brakes) Proportioning (rear brakes)

Combination Valve

Brake systems must be able distribute braking force to the wheels as evenly as possible to prevent wheel lock up, nose diving, brake fade.

To do so they use the combination valve.

Combination Valve

After pressurized fluid is moved from the master cylinder through the combination valve it is carried to the actuator through the use of steel or rubber brake lines.

Brake Lines

Never attempt to repair brake lines!

The wheel cylinder converts the hydraulic energy into mechanical energy to actuate the brake shoes.

Wheel/ Slave Cylinder

The wheel caliper is the actuator for disc brake systems. It is highly efficient and provides substantial leverage in the squeezing action of the brake pad against the brake rotor.

Wheel Caliper

The brake pads and shoes are the heart of the system. These components provide the stopping friction needed to apply the brakes.

The material they consist of varies from organic to man made fibers. Some contain asbestos so, proper PPE is a must when performing maintenance.

Brake pads and shoes

The Brake drum and Rotor are the final component in the Hydraulic Disc and Drum brake system.

They are made of hardened steel and designed to absorb the heat produced by the friction needed to stop the vehicle.

Brake Drum and Rotor

There is little maintenance involved in the hydraulic brake system outside of periodic cleaning, inspection and adjustment of brake pads and shoes. If the master cylinder is replaced peddle free play needs to adjusted.

The brake fluid should be inspected periodically as well and changed if discoloration or high moisture content is evident.

Maintenance

High Pressure oil, airborne partials and stored energy from springs will get you! Wear your PPE!

Who knows what the definition of Hydraulics is? Name the components in order that make up a

basic hydraulic brake system. (Be as detailed as possible “one component per student”).

Why should you not mix DOT3 and DOT 5 brake fluid?

How is braking force multiplied? What type of maintenance do you need to

perform on Hydraulic brake systems? What safety areas do you need to be aware of

when working on or around brake systems?

Review

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Next Lesson: Troubleshooting, Parts replacement and adjustment of Hydraulic Brake Systems.

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