Safety • The best source of information on the precautions and protective equipment needed when working with solvents and chemicals in the auto shop is..? MSDS [Material Data Safety Sheets] • What carcinogen [cancer causing chemical] is often found in the brake system..? Asbestos
Safety • What is the difference between a respirator and a particle mask..? Respirators use a charcoal filter that removes hydrocarbon compounds.
Safety • Name three PPE [Personal Protective Equipment] items that are essential when working on brakes..? Safety glasses. Particle mask Leather work shoes – especially steel toe safety shoes Latex gloves
VIN number • Where are two places where you can find the VIN number. Lower left corner of windshield Drivers door jamb
VIN number • Which digit of the VIN represent the model year. 10th • If the 10th digit is the letter ‘A’ the model year is..? 2010 or 1980
Basic brake theory • Heat fade • Fluid fade • Water fade • What are three types of brake fade...?
Basic brake theory • A leak in the hydraulic system • Parking brake is set • What two conditions could cause the ‘BRAKE” warning light to turn on ...? • What brake system failures will not illuminate the ‘Brake’ light..? Worn pads and shoes ABS system fault Faulty power booster
Basic brake theory • When the brakes are applied the kinetic energy of the car in motion is converted into ______ ..? Heat • On what type of vehicle is kinetic energy converted into something other than heat..? Hybrid or electric vehicle
Basic brake theory • The condition where brakes loose effectiveness because the temperature of the disc/drum is so hot that the pad/shoe friction materials begin to melt is called..? Heat fade • The loss of braking effectiveness when the brake fluid becomes so hot it boils and bubbles in the boiling fluid allow the brake pedal to drop to the floor is called..? Fluid fade
Basic brake theory • Hydraulic pressure • Air pressure • Cables • Electromagnets Correct answer – All of the above • To generate the necessary friction brake pads and shoes are pressed into the rotors and shoes by _______ ...?
Basic brake theory • Factory shop manual • AllData • Brake specification manuals • Specs printed or stamped onto parts • Name three sources of brake specifications...?
Hydraulic system 300 pounds • If 100 pounds of force is applied a master cylinder with a piston area of 1 square inch, how much force is applied to the brake pads on a caliper that has a piston area of 3 square inches...? • What is the pressure in the brake line to the caliper. 100 psi
Hydraulic system Nothing – all brake fluids are compatible. As long as the boiling point of the replacement fluid is equal to or greater than the original fluid. • What happens if you put DOT 5 fluid in a system that was designed for DOT 3 fluid...? • What happens if you put silicone fluid in a system designed for glycol fluid. Nothing – however you wont have the advantage of silicone [silicone wont damage the paint]
Hydraulic system The boiling point of the fluid will drop from 401 degrees to 284 degrees. • What happens if you fill a master cylinder with brake fluid from a bottle that has been uncapped for three days...? • Silicone fluid should not be used on cars with _________ . ABS – silicone aerates easily and is not recommended for vehicles with ABS
Hydraulic system DOT 5 fluid is silicone based fluid DOT 5.1 is glycol based fluid • What is the difference between DOT 5 and DOT 5.1 fluid...? • What is the primary advantage of silicone based fluid. If fluid is spilled onto painted surfaces silicone fluid will not cause any damage
Hydraulic system Printed on the reservoir cap • Where is the best place to find out what type of brake fluid the vehicle requires...? • What should you do if you accidently spill brake fluid on the fender of a car. Rinse it off with a garden hose – do not wipe it off with a rag
Hydraulic system • Brake fluid should be changed every _____ ...? 2 years • If the reservoir cap seal appears to be melted, stretched, swollen or otherwise distorted what needs to be done..? The system has been contaminated with engine oil, ATF or power steering fluid. The entire hydraulic system will need to be overhauled.
Hydraulic system • All Modern Cars and Trucks built after _____ use a Dual Circuit Master Cylinder ..? 1968 • Why..? Having two separate hydraulic circuits insures that we will have at least two working brakes in the event of a hydraulic failure.
Hydraulic system • When the driver takes his foot off of the brake pedal the hydraulic pressure in the wheel cylinders and calipers returns to the reservoir through the _____ in the master cylinder..? • When the piston in the master cylinder moves slightly forward. Vent port • When is the vent port closed..?
Hydraulic system • A front wheel drive vehicle will use what type of hydraulic circuit..? The brake bias on a front drive car is 70/30. If a front-rear split system was used then a failure of the front hydraulic circuit would leave only 30% brake effectiveness. Dual-diagonal • Why..?
Hydraulic system • What is the ‘advantage of a quick take up’ type master cylinder an calipers..? • Stepped bore – larger bore at the back than in the front. • Quick take up valve in the rear section of the cylinder body . Reduced brake drag for better fuel economy • What's different about the ‘quick take up’ master cylinder ..?
Hydraulic system • The customer complains that the brakes don’t hold when he’s sitting at a traffic light. The brake fluid level is between the ‘min’ and ‘max’ mark and there is no evidence of a fluid leak. On a road test you discover that the brake pedal drops ½ way to the floor when light pressure is applied to the pedal. What could be the problem..? Internal leakage in the master cylinder.
Hydraulic control valves • What is the function of the Proportioning Valve..? Prevents rear brakes from locking up under hard braking • How many proportioning valves are used on a dual-diagonal hydraulic system ..? Two • Where are they found..? On the master cylinder
Hydraulic control valves • What is the function of the metering valve..? Delays the application of the front disc brakes until the rear brake shoes come into contact with the drum. • What type of brake systems use metering valves..? Rear wheel drive vehicles with front disc / rear drum brakes. • Where are they normally found..? In the combination valve
Hydraulic control valves • What is the function of the differential pressure valve..? Turns on the brake failure warning light when there is a difference in pressure between the front and rear outlets of the master cylinder. • Where is it normally found..? In the combination valve • On what type of car would you expect to see a differential pressure valve Older rear wheel drive car or truck
Hydraulic control valves • What is the function of the axle height valve..? Reduces the pressure applied to the rear brakes when the vehicle is lightly loaded – increases the pressure when it is heavily loaded. • Where is it normally found..? Above the rear axle
Brake warning light • The customer complains that the brake light does not turn on when the parking brake is applied. A quick check confirms this. What would you check first..? The fuse for the brake warning light. • How do you identify what fuse controls the brake warning light..? Find the schematic in AllData. The fuse number should be on the schematic. • If your test light does not illuminated when you touch either test terminal of the fuse, the fuse is ________..? Unknown – the circuit is not turned on.
Brake warning light • The customer complains that the brake light is on all the time. The parking brake is fully released and the fluid level is just below the max mark. The vehicle uses a low fluid level switch in the master cylinder What would you check first..? Disconnect the wiring harness connector to fluid level switch and see if the light goes out. • If the light stays on what do you check next..? Disconnect the parking brake switch. If the light goes out the switch is faulty if it stays on there is a short in the wiring harness.
Brake bleeding • What are two reasons for bleeding the brake hydraulic system..? The system has been opened to replace a component and air has gotten into the system. Periodic replacement of the fluid is needed to replace brake fluid that has become saturated with water resulting in a lower fluid boiling temperature. • Name three methods of bleeding ..? Foot bleeding. Pressure bleeding. Vacuum bleeding.
Brake bleeding • How does water get into a sealed hydraulic system..? Through the process of osmosis where small amounts of water can pass through the rubber in the flexible brake hoses • The brake hydraulic system has been contaminated with engine oil. The master cylinder, calipers and wheel cylinders have been replace. What to you do to the steel brake lines ..? Flush with denatured alcohol
Brake bleeding • If the left side caliper is installed on the right wheel and vice-versa what will happen..? The system cannot be bled because the bleeders are now at the bottom of the caliper. • If the bleeder is broken off in the caliper what should be done..? Install a new/remanufactured caliper.
Brake bleeding • True / False: If you are replacing the front rotors and calipers and do not do anything to the rear brakes you only need to bleed the front brakes T/F..? False: whenever bleeding brakes all 4 wheels should be bled. There may be no air in the rear hydraulic system but if you bleed only one axle you have a high boiling point on one axle and a low boiling point on the other. • True / False: If the bleeder is broken off in the caliper you can still bleed the wheel by loosening the banjo bolt where the flex hose connects to the caliper..? False. The banjo bolt connects to the bottom of the caliper – any air in the caliper will remain there and the fluid in the caliper will have a low boiling point.
Brake bleeding • After filling the bleeder ball with fresh brake fluid the technician pressurizes the fluid by..? Adding air pressure to the Schrader valve with a tire chuck.. • After connecting the pressure adapter to the master cylinder the technician must ________ before he opens the bleeder screws at the wheels. Bleed any air out of the hose and adapter.
Brake bleeding • When foot bleeding the brake pedal can only be released or pumped when the bleeder screw is ? Closed • Foot bleeding the brakes should be continued until _________________________ ..? The fluid exiting the bleeder has no air bubbles and is clear in color.
Brake bleeding • Why is it important to top off the fluid level in the master cylinder after bleeding each wheel? If the fluid reservoir is allowed to run dry -, air will get into the system requiring that the processed be started over. • If the rubber cap is not installed on the bleeder screw after bleeding..? The bleeder will clog up with dirt and you will not be able to bleed the system without first cleaning the bleeders the next time the hydraulic system is bleed.
Master cylinder service • What is the first step in replacing a master cylinder.? Disconnect the battery negative cable. • Why disconnect the battery..? To prevent anyone from starting the vehicles – as there will be no service brake with the master cylinder removed. • Why disconnect the negative cable..? If the wrench used to disconnect the battery terminal accidently contacts vehicle ground there will be no electrical arcing.
Master cylinder service • What type of wrench is required to disconnect steel brake line nuts .? A flair nut wrench. • What will happen if an open end wrench is used..? The flats of the nut may be rounded – possibly requiring replacing and reflairing the line . • ISO bubble flair nuts have _________ threads..? Metric
Master cylinder service • Before installation a new or remanufactured master cylinder the new master cylinder should be .? Bench bled. • What tool is normally used to bench bleed the master cylinder..? Two short lengths of steel brake line with nuts, bent to allow their open ends to be inserted into the reservoir. • Brake fluid spilled onto the inner fenders and body during master cylinder replacement should be cleaned of with _________..? Water – using a garden hose
Wheel cylinders • Wheel cylinders are bolted to the ________..? Backing plate. • A mechanic is inspecting a vehicles brakes. He pulls the wheel cylinder dust boot away from the cylinder and sees that is perfectly dry inside the boot. What does this indicate..? The wheel cylinder is in good operating condition.
Wheel cylinders • Why is the function of the spring inside the wheel cylinder It holds the seal firmly against the bore surface when there is no hydraulic pressure. • How is the piston seal attached to the piston..? It’s not.
Calipers • True / False : Plastic pistons are often used in brake calipers …? True: Phenolic resin plastic pistons are used because they prevent the transfer heat from the pads to the fluid better than steel • True / False: Rusted and pitted steel pistons can be cleaned with 400 grit sandpaper and reused..? False. Any sign of pitting or rusting requires the piston or caliper be replaced.
Calipers • Caliper pistons are removed using..? Air pressure and a rubber tip blow gun. • True / False: The caliper piston seal is held inside a groove in the caliper bore ..? True. • The caliper piston seal is what type of seal..? Square cut o-ring
Calipers • What happens when the caliper dust boot has holes in it..? Water gets between the piston and cylinder bore resulting in the caliper seizing up. • True / False: Calipers can be rebuilt in the field..? True. • Prior to reassembling the caliper the caliper bore should be cleaned with..? BrakeKleen or alcohol
Steel brake lines • Steel brake lines that feed 2 wheel cylinders or calipers are normally _______________ ..? ¼” i.d. or 8 mm • Steel brake lines that feed only one wheel cylinder or caliper are normally _______________ ..? 3/16” i.d. or 6 mm • Brake lines with ISO bubble flair fittings have ________ threaded flair nuts..? Metric
Steel brake lines • When fabricating steel brake lines ____ or larger a bending tool with a mandrel is needed ..? 1/4” or 8 mm • You are replacing the ¼” brake line that runs from the combination valve to a fitting above the rear axle. It’s 100 inches long and the maximum length of line available id 60’. What do you do..? Install a ¼” union between two 60” lines and trim to the correct length. • What happens when you bend a 1/4” brake line without a bending tool..? It kinks
Flexible brake lines • The purpose of the white stripe printed on a brake hose is ..? To determine how much twist is in the hose • A banjo bolt is normally used to ..? Connect the flex hose to the caliper. • Two _______are needed to seal the banjo fitting, and bolt head to the caliper..? Copper washers
Flexible brake lines • What's the difference between a banjo bolt and a regular bolt ..? The banjo bolt is hollow and is cross drilled at the neck to allow fluid to pass through it • What is the function of the liner on the inside of the hose..? Prevents water from being absorbed through the rubber • True / False: A collapsed inner liner can cause the brake to remain applied after the driver takes his foot off of the brake pedal..? True
Wheel bearings • The two forces acting on a wheel bearing are..? Radial Axial or lateral • The weight of the vehicle is a ______ load on the bearing..? Radial • The sideways force applied to the wheel bearing during cornering is an ___________ load ..? Axial
Wheel bearings • Name the four parts of a ball or roller bearing..? Balls or rollers Inner race Outer race Cage • Name the three types of wheel bearings used on cars and light trucks..? Ball bearing Tapered roller bearing Cylindrical [straight] roller bearing