1. Brake System Fundamentals
Chapter 71

2. Basic Brake System
Brake lines Emergency brake Brake pedal assembly Master cylinder Brake booster Wheel brake assembly
Metal tubing and rubber hose that transmit pressure to the wheel brake assemblies.
Mechanical system for applying rear brake assemblies
Foot lever for operating the master cylinder and power booster.
Hydraulic-piston pump that develops pressure for the brake system.
Vacuum or power steering operated device that assists brake pedal application.
Devices that use system pressure to produce friction for slowing or stopping wheel rotation.

3. Drum and Disc Brakes
Caliper - assembly that holds the cylinder, piston, and brake pads.

4. Drum and Disc Brakes
Caliper cylinder - machined hole in the caliper; the piston fits into this cylinder.

5. Drum and Disc Brakes
Brake pads - friction members pushed against the rotor by the action of the master cylinder, caliper cylinder, and piston.

6. Drum and Disc Brakes
Rotor - metal disc that uses friction from the brake pads to stop or slow wheel rotation.

7. Drum and Disc Brakes
Wheel cylinder - houses hydraulic pistons that are forced outward by fluid pressure and is found on drum brakes.

8. Drum and Disc Brakes
Brake shoes - friction units that are pushed against the rotating brake drum by the action of the wheel cylinder assembly.

9. Drum and Disc Brakes
Brake Drum - rubs against the brake shoes to stop or slow wheel rotation.

10. Braking Ratio
Typically the front brakes handle 60-70% of the braking power, while the rear brakes handle 30-40% of the braking. Front wheel drive vehicles have even a higher braking ratio at the front wheels.

11. Brake System Hydraulics
Pascal’s Law
Liquids in a confined area will not compress, however, air in a confined area will compress.
When pressure is applied to a closed system, pressure is exerted equally in all directions.
A hydraulic system can be used to increase or decrease force or motion.

12. Brake System Components
Brake Pedal Assembly - Foot lever for operating the master cylinder and power booster.

13. Brake System Components
Master Cylinder –
It is a foot operated pump that pumps brake fluid.
Helps equalize the pressure required for braking.
Keeps the system full of brake fluid.
It maintains a slight pressure to keep contaminants (air & water) from entering the hydraulic system.

14. Brake System Components

15. Brake System Components
Vacuum Booster Hydraulic Booster
Brake Boosters
Vacuum brake boosters use engine vacuum to help stop the vehicle.
Hydro-boost systems use pressure created by the power steering pump to help stop the vehicle.
All brake boost systems are designed to help stop the vehicle.

16. Brake Fluid Brake Fluid DOT 3 Standard Brake Fluid
DOT 4 Hi-Temp Brake Fluid
DOT 5 Silicone Brake Fluid
Keep brake fluid in tightly sealed containers.
Should be flushed every 2 years regardless of mileage!

17. Brake System Components
Disc Brake Components
1 Caliper assembly 2 Bracket mounting bolt 3 Bleed screw 4 Dust cap 5 Anti-rattle spring 6 Guide bolt 7 Brake pad wear warning light wire 8 Cable clamp 9 Brake disc 10 Allen bolt 11 Shield 12 Bolt 13 Washer 14 Plug 15 Plug 16 Caliper bracket 17 Cable clamp 18 Piston seal, piston, dust boot and circlip 19 Guide bush repair kit 20 Brake pads

18. Brake System Components
Drum Brake Components

19. Brake Warning Lights
The brake warning light switch warns the driver of a pressure loss in a dual brake system.
The Low-Fluid Warning Light Switch lets the driver know when the brake fluid is low.

20. Brake System Control Valves
Proportioning Valve is used to equalize braking action in systems with front disc brakes and rear drum brakes.
Metering Valve is used to regulate the pressure going to each wheel cylinder.
Combination Valve is a single unit that functions as a brake warning light switch, a metering valve, and a proportioning valve.

21. Parking Brakes
Parking brakes provide a mechanical means of applying the brakes.
Parking brakes can use either drum or disc brakes.
Parking brakes should never be used to help stop the vehicle during normal driving.
Parking brakes need periodic inspection and adjustment.
A hand operated emergency brake should make 4-5 clicks when engaging it (not more)

22. QUESTIONS? Please refer to textbook chapter 71