2. Brake System Design
• The front brakes have 75-90% of the
stopping power
• Systems are split in 2 ways
– Diagonal
– Front/Rear
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3. Master Cylinder
• The master
Cylinder is bolted
to the Brake
Booster and is
located on the
bulkhead
• Pressurizes brake
fluid when service
brake pedal is
depressed
• The reservoir
holds the brake
fluid
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5. Brake Fluid
• Brake fluid comes in several types
– DOT 3, 4, 5
– Most common today is Polyglycol
DOT 3 and DOT 4
– Both collect water because their
Hydroscopic
– DOT 3 Min boil point 410 dry 284 wet
– DOT 4 Min boil point 446 dry 311 wet
– DOT 5 Min boil point 500 dry 356 wet
• Silicone type should not be mixed
with 3 or 4
NEVER MIX PETROLEUM BASED
PRODUCTS WITH BRAKE
SYSTEMS!
Always add fluid
from unopened
container!
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6. Power Assist Units
• Vacuum Booster most
common
• Some cars and trucks
have HydroBoost
brake boosters
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7. Vacuum Booster
• The Vacuum Booster
is supplied vacuum
from the engine
• A “Check Valve”
keeps vacuum in
booster when engine
is off
8
11. Drum and Rotor Issues
• Metal to Metal Drums and Rotors
– Friction material completely worn out
– Usually requires replacement of component
• Out of Round Drum or Warped Rotor
– Drum and Rotor can be “Turned” true
• Hot Spots or cracking
– Component should be replaced and cause of
overheat diagnosed
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12. Brake Issues
• Low, but hard brake pedal
– Worn brake shoe linings
– Misadjusted brake shoe linings
• Inspect and adjust
• Spongy brake pedal, may “pump” up
– Possible bent parts from accident
– Air in lines / calipers or wheel cylinders
• Bleed System
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13. Brake Issues
• No or Low brake pedal - LOOK OUT!!! I’m
coming through…
– Hydraulic leak in system
– Bypassing master cylinder
– Low brake fluid
• Check fluid level
• Check for leaks
• Check master cylinder
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