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Basic Brakes. Split systems/dual master cylinders s Used exclusively since 1960s s Most use front/rear split s Some use diagonal split.

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Presentation on theme: "Basic Brakes. Split systems/dual master cylinders s Used exclusively since 1960s s Most use front/rear split s Some use diagonal split."— Presentation transcript:

1 Basic Brakes

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

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

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

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

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

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

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

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

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

11 Common hydraulic valves s Pressure differential valve s Metering valve s Proportioning valve

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

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

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

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

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

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

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

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

20 Drum/rotor resurface s Demo on car

21 Brake bleeding s Demo on car


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