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Basic Brakes.

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Presentation on theme: "Basic Brakes."— Presentation transcript:

1 Basic Brakes

2 Split systems/dual master cylinders
Used exclusively since 1960’s Most use front/rear split Some use diagonal split

3 Brake Fluid Use DOT 3 in virtually all cars
Never ever mix with petroleum based liquids When cleaning brake parts use only brakeclean, clean brake fluid, or denatured alcohol Very hygroscopic Some manufactures recommending flushing intervals

4 Master cylinder Primary piston is acted on by pushrod
Secondary piston is acted on by hydraulic pressure Each piston will have it’s own: Compensating port Vent (relief) port Return spring Reservoir

5 Master cylinder diagnosis
Usually fails with one cup bypassing Low or no fluid pressure from one side of cylinder Low pedal with brake light coming on Moisture or petroleum in cylinder will destroy/swell cups

6 Master cylinder repairs
Rebuilding rare today Most “new” are rebuilt MUST be bench bled before installation If done completely system bleeding will not be necessary

7 Power boosters Can be vacuum or hydraulic boosted
Vacuum uses engine vacuum to assist pedal travel Hydraulic shares power steering pressure off of pump to assist pedal Both have fail safe if booster fails Fail-safe will require increased pedal effort

8 Vacuum booster testing
Pedal will fall away when engine started Will store vacuum for two or three applications If vacuum leaks off possibly check valve leakage or internal leakage Brake fluid in booster indicates failed master cylinder and both must be replaced

9 Brake hoses and lines Steel lines are double wall
Use special double flare ISO flare steel or brass fittings Never use single flare or compression fittings Hoses Usually double lined hoses Lines on hose body should not twist when installed

10 Brake hoses and lines problems
Hoses can balloon only under pressure causing spongy brakes Inner wall can block off flow/pressure Metal lines can rust from inside out

11 Common hydraulic valves
Pressure differential valve Metering valve Proportioning valve

12 Drum brake Duo-servo vs. non-servo Shoes Drums Primary / secondary
Riveted vs. bonded Asbestos still around Drums Usually cast iron Must carry heat away

13 Drum brake service Drum removal
Can be rusted around center of drum Imports may have threaded removal holes May need to adjust down shoes If shoes are wet with brake fluid, oil, grease shoes must be replaced Drums should be resurfaced All dust MUST be wetted down or vacuumed away

14 Drum brake service Shoes should be replaced one side at a time for comparison purposes Usually remove return springs first, hold downs second Any weak or stretched spring needs new hardware kit

15 Drum brake service Adjuster should be cleaned and lubricated
Baking plate pads need lubrication Roll back dust boots for inspection Any grease or brake fluid on shoes should be cleaned off before installation

16 Drum brake problems Squealing when applied Fading Pulsating pedal
Must isolate front or rear Snapping or clicking noise Grinding when applied Low brake pedal Locked up on very cold days

17 Disc brake Two categories Calipers containing one or two pistons
Fixed Moving Calipers containing one or two pistons Floating caliper and sliding caliper must move freely Rotors usually cast iron - can be vented or solid Pads often will have wear indicators

18 Disc brake service Most require R&R of calipers
Slides and pins must be cleaned and lubed Some pads have anti-rattle plates or require anti-squeak adhesive to back of pads or will have retaining tabs As pads wear fluid level will drop Piston must be bottomed in bore DO NOT allow caliper to hang by hose

19 Disc brake problems Pulsating brakes very common
Binding caliper piston or slides

20 Drum/rotor resurface Demo on car

21 Brake bleeding Demo on car

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