Brakes

On a car with disc/drum brakes, the front brakes grab quickly when light pedal pressure is applied. This problem could be caused by a bad:
A. proportioning valve
B. pressure safety switch
C. metering valve
D. residual check valve
C. The metering valve delays the flow of brake fluid to the front calipers until the pressure in the system rises to a point where the wheel cylinder can overcome the tension of the brake shoe return springs. The purpose is to have both front and rear brakes apply simultane ously. This prevents the front brakesfrom locking up during light brake applications.

The driver of a vehicle with power disc/drum brakes says that the brake pedal moves slowly to the floor while maintaining pedal pressure at a stoplight. What could cause this problem?
A. leaking primary piston cup in mast cylinder
B. leaking power brake booster
C. leaking residual check valve in master cylinder
D. internal leak in the combination valve
A. If the primary piston cup in the master cylinder is leaking pressure will not build up ahead of the primary piston to increase pressure to the rear brakes. The piston will then move forward until the spring is compressed enough to move the secondary piston. Consequently, this internal leak will cause the brake pedal to slowly drop to the floor.

Which of the following would MOST LIKELY happen if the measurements taken from the check shown above varied from the manufacture’s specifications?
A. noisy brake operation
B. brake grab or pull
C. pulsating brake pedal
D. low brake pedal
C. Poor rotor parallelism (thickness variation) will cause a pulsating brake pedal. This is due to the caliper piston movement that occurs as the pad rides over the alternating high and low areas on the disc. This action forces brake fluid to flow back and forth from the caliper to the master cylinder, creating the pulsating pedal feedback.

What is the purpose of the master cylinder residual check valve(s) on vehicles equipped with drum brakes?
A. allows the driver to pump up the brakes
B. prevents air from entering the hydraulic system
C. prevents wheel lockup by reducing the hydraulic pressure
D. reduces pedal pulsation by controlling hydraulic pressure
B. Residual check valve(s) are used on drum brakes to keep residual low pressure (slight static pressure) in the brake system at all times even when the brake pedal Is released. This pressure (5-20 psi) keeps the lips of the wheel cylinder piston cups tight against the cylinder walls to prevent air from entering the system when at rest (brakes released).

A tech has just overhauled the front brakes on a vehicle with front disc and rear drum brakes. However, when he attaches a pressure bleeder (pressurized to about 25 psi) to the master cylinder, he cannot get any fluid to come out of the disc brake caliper bleeder screws. Which of the following is MOST LIKELY the cause?
A. bad proportioning valve
B. bad pressure differential valve
C. proportioning valve release button not activated
D. metering valve released button not activated
D. A metering valve requires a minimum pressure (typically between 75-125 psi) to open. At this point pressurized fluid Hows to the front calipers. Since the bleeder tank is only pressurized to 25 psi, fluid pressure is too low to open the metering valve during this procedure. Therefore, when you use a pressure bleeder on a system with a metering valve, you must manually keep the valve open by either pushing the button in on the end of the valve, or pulling the stem outward on the end of the valve.

On a vehicle with single piston floating caliper front disc brakes, the brake pads on the left side of the vehicle are almost completely worn while the right side is almost new. Tech A says that too much rotor runout could be the cause. Tech B says that a binding caliper piston could be the cause. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
B. Excessive rotor runout would cause a pulsating brake pedal, but not uneven side-to-side pad wear. A frozen caliper piston on the other hand, will keep both inner and outer brake pads equally applied against the rotor even when the brake pedal is released. This constant friction will cause rapid pad wear in the affected caliper as well as a front-end pull.

What is the purpose of the bar that is being removed from the brake assembly shown below?
A. to equalize the braking force between the shoes during normal braking
B. to center the shoes after each brake application
C. to force the shoes into the drum when the parking brakes are applied
D. to reduce the distance between the shoes and the drum
C. The parking brake strut bar forces the brake shoes into the drum when the parking brake is applied.

A hydraulic brake line is leaking. Which of the following is the correct repair procedure?
A. Cut out the bad section and replace the new steel tubing using compression fittings.
B. Replace the leaking line with double-flared, seamless copper tubing.
C. Cut out the bad section and replace with single-flared steel tubing using flare nuts and unions.
D. Replace the leaking line with double-flared steel tubing.
D. Steel tubing of the same size, type, and length with double flared ends must be used when replacing a traditional SAE double inverted flare style hydrau lic brake line.

The set-up shown above is used to check:
A. rotor parallelism
B. wheel bearing adjustment
C. rotor lateral runout
D. rotor face wear
C. Lateral runout is the move ment of the rotor from side to side as it rotates on the steering knuckle spindle. The dial-indicator set-up shown in the illustration is used to make this measurement once the wheel bear ing nut has been tightened (bearing play removed).

Which of the following problems would be caused by using a residual check valve in a disc brake master cylinder?
A. reduced brake pedal travel
B. reduced brake system pressure
C. increased brake pad wear
D. increased rotor runout
C. If a residual check valve was installed in a disc brake master cylinder, it would cause in-creased brake pad wear since the residual brake pressure would cause the caliper pistons to keep the pads applied even when the brake pedal is released.

A customer complains that their vehicle pulls to the right when the brakes are applied. Tech A says a restricted brake line to the left caliper can cause this problem. Tech B says a malfunctioning proportioning valve is probably the cause. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
A. A restriction in the brake line will cause a drop in fluid pressure to the affected caliper. This will cause the caliper to be unable to exert the same force against the pads as the unrestricted side. Because of this, the vehicle will pull to the side where the pressure is highest and brake force is greatest. In this case, that would be the right side.

With foot pressure applied, the brake pedal on a vehicle with vacuum assisted power brakes moves down slightly when the engine is started. Tech A says that this condition can be caused by a leaking power brake booster diaphragm. Tech B says that the cause could be a faulty power brake booster check valve. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
D. With the brake pedal applied while starting the engine, the pedal should move down slightly indicating that the vacuum booster is operating properly.

Tech A says that the tool shown above is used to adjust the brake shoes. Tech B says that the tool shown above is used to determine the inside diameter of the drum. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
A. The illustration shows a technician setting a brake shoe adjustment gauge, or caliper, to the inside diameter of a brake drum. The other side of the gauge is then positioned over the brake shoes and the star wheel turned until the shoes tightly contact each end of the gauge. Technician B is wrong because a brake drum micrometer is used to measure the inside diameter of a brake drum.

The hydraulic system on a vehicle with integral ABS is to be bled. Tech A says that the front brakes can be bled in a conventional manner. Tech B says that both front and rear brakes can only be bled using the pressure from a fully charges accumulator. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
A. The front hydraulic circuits in an integral ABS system can be bled in the conventional manner since it is the booster piston in the hydraulic modulator assembly that supplies fluid to the front brakes. However, the rear circuit is dependent upon boost pressure from the accumulator, which means the accumulator must be fully charged in order to bleed the rear brakes.

A driver complains that the ABS system on his car engages every time he applies the brakes on a cobblestone roadway he uses going back-and-forth to work. This condition means that:
A. The system is operating normally.
B. The wheels are traveling at different speeds.
C. A wheel speed sensor(s) is faulty.
D. both A and B
D. When a vehicle with ABS is braked on abnormally irregular road surfaces, like a cobblestone road, the wheels decelerate at different speeds. Because the sigtlals coming from the wheel speed sensors under this condition are not in sync with each other, the ABS control unit interprets this as impending wheel lockup and responds by engaging the system.

Two technicians are discussing the duo-servo type drum brake design. Tech A says the brake lining on the secondary shoe is usually longer and thicker than the brake lining on the primary shoe. Tech B says the primary shoe is installed toward the rear of the vehicle. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
A. In a duo-servo drum brake design under normal forward braking, the friction developed by the secondary lining is greater than the primary lining. Therefore, the secondary shoe is typically longer and thicker than the primary shoe. The primary shoe is installed facing the direction of forward motion.

All of the following statements about leading-trailing type drum brakes are true EXCEPT:
A. The leading shoe does most of the forward braking.
B. Both brake shoes are held against a fixed anchor on the backing plate.
C. They are self-energizing.
D. The trailing shoe does most of the reverse braking.
C. The leading-trailing drum brake design is not self-energizing. This is due to the fixed anchor on the backing plate, which prevents the shoes from transferring their force to one another.

Tech A says that DOT 5 brake fluid has a lower boiling point than DOT 4. Tech B says that DOT 4 brake fluid is silicone-based and should never be used in an ABS system. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
D. It is DOT 4 brake fluid that has a lower boiling point, and DOT 5 that is silicone-based and should not be used in any ABS system.

Brakes that drag or fail to release can be caused by which of the following conditions in the master cylinder?
A. leaking primary cup
B. leaking secondary cup
C. failure of the residual pressure check valve
D. clogged compensating port
D. The compensating port allows for residual hydraulic line pressure to be discharged into the reservoir as the brake pedal is released. A clogged or restricted compensating port will create a pressure build-up, which will cause the brakes to drag or fail to release. The port can be dogged by foreign matter, blocked by a swollen primary cup or covered by the primary cup if the master cylinder pushrod is improperly adjusted.

All of the following could cause a hard brake pedal on a vehicle with power brakes EXCEPT:
A. an engine with the valves adjusted too tight
B. brake fluid on the linings
C. a leak in the brake hydraulic system
D. a frozen caliper
C. A leak In the hydraulic system wouldn’t cause a hard pedal, but rather create the exact opposite condition due to the hydraulic pressure loss. An engine with the valves adjusted too tight would develop low vacuum. This would adversely affect the operation of the power brake booster and cause a hard pedal. Brake fluid on the linings will cause the friction material to grab resulting in a hard pedal, while a frozen caliper would prevent retraction of the piston resulting in a similar condition.

Tech A says that a caliper seal installed in the caliper bore is called a stroking seal. Tech B says that when the brake pedal is released, the piston in the caliper moves back in its bore due to the action of the piston seal. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
B. (C) ?? The outward movement of the caliper piston during brake application causes the piston seal to distort. Once the brakes are released however, the seal returns to its original shape forcing the piston to retract in its bore. A caliper seal that is installed on the piston Is known as a stroking seal.

When replacing disc brake pads, you must bottom the caliper piston in its bore to create room for the new pads. Which of the following is the proper procedure?
A. Use a C-clamp or pliers to slowly bottom the piston in the caliper.
B. Remove half the fluid from the master cylinder reservoir, then use a C-clamp or pliers to slowly bottom the piston in the caliper.
C. Connect a hose to the caliper bleeder screw and insert the other end of the hose into a suitable C-clamp or pliers to slowly bottom the piston in the caliper.
D. Remove the caliper from the vehicle, then use a C-clamp or pliers to slowly bottom the piston in the caliper.
C. By opening the bleeder screw on the caliper, contaminated fluid is not forced back into the master cylinder (or on ABS vehicles, into the hydraulic control unit). Answer B is wrong because, while it will work, doing so can cause problems in the hydraulic system. Answer A is wrong because, without checking the fluid level or opening the bleeder screw, fluid could be forced into and spill out of the master cylinder reservoir. Answer D is wrong because caliper removal is not necessary.

Tech A says that all 3-channel ABS systems use only 3 wheel speed sensors. Tech B says that a 4-channel ABS system means that fluid pressure is independently regulated to each of the wheels during an ABS stop. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
B. The number of wheel speed sensors used on an ABS system does not necessarily indicate the number of channels the system has. A channel is an independently controlled fluid path from the hydraulic modulator to the wheel. Therefore, a 3-channel system on a car can have a wheel speed sensor at each wheel, even though there are only 3 individually controlled hydraulic circuits: two in the front, and one in the rear.

Tech A says that when a rotor is machined, an equal amount of material must always be removed from both sides. Tech B says that the minimum thickness dimension cast into the rotor is the dimension that the rotor can be machined to. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
D. The minimum thickness dimension cast into the rotor is usually the discard dimension. The rotor should not be machined closer than 0.0310-in. to this dimension in order to allow for wear. When machining a rotor, you do not have to remove an equal amount of material from both sides if the vehicle has floating or sliding calipers. However, on fixed calipers an equal amount must be machined from both sides.

The purpose of an anti-lock brake system is to maintain tire (wheel) slip at what level?
A. a level between 50-75%
B. 100%
C. 0%
D. a level between 10-20%
D. Maximum braking effectiveness is achieved when tire slip is maintained at a level between 10-20%.

While on a road test, a technician notices that the rear wheels lockup and the car skids when attempting to stop quickly from a high speed. The MOST LIKELY cause of this problem is a defective:
A. residual pressure check valve
B. pressure differential valve
C. metering valve
D. proportioning valve
D. The proportioning valve reduces the pressure applied to the rear wheel cylinders in rela tion to the pressure applied to the front calipers under heavy braking. A defective proportioning valve can cause the rear wheels to lock and skid during sudden stops because the fluid pressure to the rear wheel cylinders would be unregulated.

Excessive slack in the parking brake cables can be eliminated on most vehicles by making an adjustment at the :
A. equalizer
B. star wheel adjusters
C. strut rod
D. pushrod
A. On most vehicles, parking brake adjustment consists of shortening the length of one or more cables to remove excessive slack. This adjustment is generally made by tightening an adjusting nut at the equalizer.

A customer complains that the brake warning light comes on whenever the brake pedal is depressed while driving. All of the following could cause this to occur EXCEPT:
A. a leak in the rear half of the hydraulic system
B. a short to ground in the warning light circuit
C. a leak in the front half of the hydraulic circuit
D. a leaking pressure differential switch
B. Any leak in the hydraulic system that causes unequal pressure to be applied to one side of the pressure differential piston will cause the warning light to illuminate. The only choice here is a short to ground in the light. This failure would cause the light to stay on all the time regardless of hydraulic condition.

The MOST common cause for premature front brake pad wear in a disc/drum system is:
A. seized calipers
B. faulty master cylinder
C. improperly adjusted rear shoes
D. malfunctioning metering valve
C. While all of the choices listed could cause the pads to wear prematurely, the most com mon cause of this condition is when the rear shoes are incorrectly adjusted. Since the majority of braking action is done by the front brakes (especially on front-wheel-drive cars), it is imperative that the rear shoes are adjusted properly. This will help balance brake action as well as lining wear.

Tech A says that DTCs can be accessed from any ABS system using flash diagnostics. Tech B says that ABS system tests can be performed with a bi-directional scan tool. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
B. Only a few ABS systems (primarily RWAL) offer flash code diagnostics for retrieving stored fault codes. A bi-directional scan tool can be used to perform tests on ABS system components. A technician can activate solenoids and valves while observing the change in that circuit.

To determine if an intermittent ABS problem is related to an erratic wheel speed sensor signal, which of the following should be used?
A. ohmmeter
B. voltmeter
C. scan tool
D. digital storage oscilloscope
D. Answers B and C are incorrect because the sampling rates are too low. An intermittent can be seen with the digital storage oscilloscope (DSO) because it samples the electrical signal over 250,000 times per second.

A few minutes after the engine was turned off on a vehicle with vacuum power assist, the brake pedal is applied and it is hard to push. Tech A says that this is a normal condition. Tech B says that the booster check valve is leaking. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
B. Technician A is incorrect because there should be at least one power assist before the pedal gets hard to push. Technician B is correct because the lack of power assist indicates that the check valve is leaking.

The above measurement is made when replacing all of the following EXCEPT:
A. master cylinder
B. vacuum power booster
C. brake caliper
D. master cylinder pushrod
C. Replacing a disc brake caliper would not require measuring master cylinder pushrod length. Measuring pushrod length may be required when re placing any of the other components.

During a brake inspection, an area of the vacuum brake booster below the master cylinder is found to be damp. Tech A says that this is a normal condition. Tech B says that any evidence of fluid indicates a leak and the master cylinder must be replaced. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
A. A small amount of fluid present here is normal due to the lubricating action of the master cylinder bore end seal. The brake fluid is kept from leaking back into the power booster by a seal on the pushrod. If a large amount of fluid is present, unbolt the master cylinder from the booster and look for signs of leakage.

Tech A says that tapered roller bearings can be adjusted using a torque wrench. Tech B says that tapered roller bearings are adjusted using a dial indicator. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
C. Both methods are commonly used to adjust tapered roller bearlngs. Consult the vehicle service manual for the spe cific adjustment procedure.

All of the following could cause a pulsation to be felt in the brake pedal EXCEPT:
A. brake drum out of round
B. normal ABS operation
C. lateral rotor runout
D. seized caliper piston
D. A seized caliper piston can cause a brake pull or a hard pedal, but it would not cause a pedal pulsation. All of the other choices can cause a pulsation to be felt through the brake pedal.

Tech A says that, when testing a proportioning valve, the pressure at the outlet port to the rear brakes should rise at a faster rate, once transition pressure is reached. Tech B says that vehicles with diagonally-split hydraulic systems must have the proportioning valve tested twice. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
B. Vehicles with diagonally-split hydraulic systems have dual proportioning valves, so if a problem is suspected, both valves must be tested. Technician A is incorrect because, when testing a proportioning valve, the pressure of the outlet to the rear brakes will rise at a slower rate, once transition pressure is reached.

All of the following disc brake rotor measurements can be performed using a micrometer EXCEPT:
A. parallelism
B. thickness
C. runout
D. taper
C. Lateral runout is measured using a dial indicator. All of the other measurements can be made using a micrometer.

Which of the following disc brake caliper designs usually allow the brake pads to be removed without removing the caliper?
A. fixed
B. floating
C. sliding
D. all of the above
A. The disc brake pads can usually be removed from fixed calipers while the caliper is mounted in place. Floating and sliding calipers require that the caliper be removed or pivoted out of the way to access the disc brake pads.

After applying the brake pedal several times to deplete the fluid reserve in the accumulator of a Hydro-Boost system, a tech applies the brake pedal with moderate pressure and starts the engine. What should the tech feel at the pedal if the Hydro-Boost system is operating properly?
A. The pedal should initially rise before moving downward.
B. The pedal should initially move downward before rising up.
C. The pedal should move downward.
D. The pedal should rise.
B. If the Hydro-Boost system is operating properly, the brake pedal should initially move downward before rising up against foot pressure.

All of the following can cause disc brake squeal EXCEPT:
A. loose or missing anti-rattle springs
B. grease on the linings
C. glazed linings
D. dirt embedded in the linings
B. Brake linings that are con taminated with grease, oil or brake fluid can cause the vehicle to pull when the brakes are applied, but would not cause brake squeal.

Tech A says that when rebuilding a caliper with a stroking seal, the condition of the caliper bore surface is critical. Tech B says that when rebuilding a caliper with a fixed seal, the condition of the piston surface is the most important consideration. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
C. A stroking seal is located in a groove in the caliper piston and moves with the piston. The lip of the seal rides against the surface of the caliper bore, so the caliper bore must be smooth to prevent leaks. A fixed seal is installed in a groove in the caliper bore. It seals against the outside surface of the caliper piston, so that surface must be in good condition to provide a good seal.

All of the following can cause a vehicle to pull to one side when the brakes are applied EXCEPT:
A. seized caliper piston
B. worn strut rod bushings
C. blocked master cylinder compensating port
D. brake fluid soaked linings
C. A blocked master cylinder compensating port could cause all brakes to drag but would not cause a brake pull. All of the other choices could cause brake pull.

Tech A says that ABS wheel speed sensor gap should be adjusted with a non-magnetic feeler gauge. Tech B says that a paper spacer can be used to adjust ABS wheel speed sensor gap but the paper must be removed before the vehicle is operated. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
A. New wheel speed sensors come with the paper spacer installed but it Is not necessary to remove it; the spacer is designed to wear off during vehicle operation.

When discussing wheel bearings, all of the following statements are true EXCEPT:
A. Tapered wheel bearings are most commonly used on drive axles.
B. Sealed ball bearings are not adjustable.
C. A new grease seal should be installed when bearings are repacked.
D. The races on tapered wheel bearings cannot be interchanged.
A. Tapered roller bearlngs are usually used on non-drive axles. All of the other statements are true.

All of the following could cause the parking brake to not hold a vehicle on a grade EXCEPT:
A. seized cables
B. excessive rear brake shoe-to-drum clearance
C. seized wheel cylinder
D. broken parking brake linkage
C. The parking brake system engages the rear brakes mechanically; a seized wheel cylinder would not affect parking brake operation.

To determine the serviceability of a rake drum, all of the following should be checked EXCEPT:
A. diameter
B. minimum thickness
C. out-of-roundness
D. tape wear
B. Minimum thickness is checked when inspecting a disc brake rotor. All of the other measurements mentioned should be made when inspecting a brake drum.

A vehicle’s brake pedal is pumped rapidly 20 times and then held down. The master cylinder cover is then removed and when the pedal is released, a geyser is seen coming from the reservoir. Tech A says that this indicates that air is trapped in the system. Tech B says that this means that fluid is being forced out of the cylinder bore through the compensating ports and is normal master cylinder operation. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
A. Pumping the brakes com presses the air and when the pedal is released, the compressed air pushes the hydraulic fluid back through the lines, causing it to squirt. Tech B is wrong because a small squirt of fluid should appear over the reservoir, indicating that fluid is being forced out of the cylinder bore through the compensating ports, only when the pedal is applied.

Tech A says that RWAL ABS systems must be diagnosed using a scan tool. Tech B says that the ABS warning light will only come on when there is a fault in the system. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
D. Technician A is wrong because, while most Rear Wheel Anti-Lock (RWAL) systems offer flash-code diagnostics, most four-wheel ABS systems require the use of a scan tool to ex tract stored fault codes from the computer’s memory. Techni cian B is wrong because the ‘anti-lock’ warning Light will come on whenever the key is turned ON, and if there are no faults in the system, will then go out after a few seconds.

Tech A says that any imperfection found in a phenolic caliper piston warrants replacement. Tech B says that a phenolic caliper piston should be protected with block of wood when installing it into the caliper bore with a C-clamp. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
B. A phenolic piston should be protected to keep it from being damaged when a C-clamp is used. Technician A is wrong because minor surface imperfections are OK provided they do not enter the dust boot groove area.

Which of the following should be used to measure the thickness of a scored rotor?
A. vernier caliper
B. outside micrometer with flat anvil and spindle
C. inside micrometer
D. outside micrometer with pointed anvil and spindle
D. An outside micrometer with a pointed anvil and spindle is a disc brake micrometer. Unlike a standard micrometer that uses a flat surface on the anvil and spindle, a disc brake micrometer uses pointed tips so the instrument can fit into the grooves of scored rotors, to accurately measure the thickness.

During routine vehicle maintenance, the fluid level in the master cylinder reservoir is checked. When the reservoir cap is removed, purple colored fluid is found in the reservoir. Tech A says that this means the fluid should be topped off with DOT 4, which has a slightly higher boiling point than regular brake fluid. Tech B says taht this means that the fluid is contaminated; all rubber parts in the system must be replaced and the system flushed. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
D. Purple is the color of silicone fluid and only DOT 5 fluid should be used to top off the reservoir.

A complete front brake service has just been performed on a vehicle with disc brakes: rotors turned, calipers rebuilt, new brake pads, bearing repacked and adjusted. However, when the vehicle is road tested, a pulsation can be felt through the pedal. Which of the following is the MOST LIKELY cause of the pulsation?
A. non-directional finish not applied to rotors
B. wrong lining compound chosen
C. over-torqued lug nuts
D. incorrect bleeding sequence
C. Over-tightening the lug nuts can distort the color and create excessive runout, resulting in a pedal pulsation. All of the other choices may cause other problems, but not a pedal pulsation.

Brake fluid leaking from a cracked brake line causes the brake light on the dashboard to come on in response to the loss of hydraulic pressure. Which of the following valves in the hydraulic system switched on the light?
A. metering valve
B. pressure differential valve
C. proportioning valve
D. residual check valve
B. The pressure differential valve and warning switch alerts the driver of a pressure loss in one of the hydraulic circuits. The residual check valve is often used in the master cylinder outlet port of drum brake systems in order to maintain a slight pressure in the brake lines and wheel cylinders, which keep wheel cylinder pistons tight against their bores. The metering valve delays front disc brake operation until the rear brakes shoes overcome the return spring tension. The proportioning valve is used to control rear brake pressures, particularly during hard stops.

Tech A says that an integral ABS system is an add-on-system. Tech B says that a non-integral ABS system is a high-pressure system. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
D. The non-integral ABS system is added on to the ve hicles existing hydraulic brake system, and is generally a low- pressure arrangement.

The diameter of drums mounted on the same axle should measure within how many thousands of an inch of one another?
A. 0.001
B. 0.005
C. 0.010
D. 0.020
C. The diameter of brake drums mounted on the same axle must be within 0.010-in. of one another.

Absorption of 3% moisture can reduce the boiling point of DOT 3 brake fluid by what percentage?
A. 10%
B. 20%
C. 25%
D. 50%
C. Absorption of 3% moisture can reduce the boiling point of DOT 3 brake fluid by 25%.

All of the following are procedures for removing air from a hydraulic system EXCEPT:
A. bench bleeding
B. power bleeding
C. manual bleeding
D. vacuum bleeding
A. Bench bleeding is a proce dure for removing air from the master cylinder only. All of the other procedures remove air from the entire system.

All of the following can be used to apply a non-directional finish to a disc brake rotor EXCEPT:
A. sanding block
B. fine file
C. lathe attachment
D. sanding disc
B. Files are not used to apply a non-directional finish on a disc brake rotor. All of the other methods can be used to give the rotor a swirl-like finish.

All of the following can cause a problem in the Hydro-Boost system EXCEPT:
A. loose power steering pump belt
B. leaking power steering hoses
C. low power steering pump pressure
D. leaking check valve
D. A vacuum check valve is used on a vacuum power booster. The Hydro-Boost system uses power steering pump fluid pressure rather than intake manifold vacuum, so all of the other choices would apply.

A customer says that he has just replaced his front disc brake pads himself and now the ABS warning light is on. Which of the following could be the cause?
A. damaged wheel speed sensor
B. incorrect wheel speed sensor gap
C. stuck ABS solenoid valve
D. all of the above
D. Some common ABS problems can be caused by carelessness when performing basic brake service. Wheel speed sensors can be disturbed or damaged accidentally. Solenoid valves can stick if the caliper bleeder screws are not opened when the caliper pistons are retracted. Since the caliper is the lowest point in the system, dirt and corrosion naturally accumulate there. If the bleeder screws are not opened, brake fluid and these contaminants are forced backward into the system. When these contaminants find their way into the hydraulic control unit, they can cause valves to stick.

Drum brake drag cane caused by all of the following EXCEPT:
A. frozen parking brake cables
B. frozen star wheel
C. restricted brake hose
D. swelled wheel cylinder cups
B. A frozen star wheel would not cause brake drag. Rather, it would prevent the automatic adjuster mechanism from working which would gradually cause the brake shoe-to-drum clearance to increase as the linings wore. All of the other answers could cause the brake shoes to not retract from the drum, resulting in brake drag.

Tech A says the type of fitting shown above is common to all brake systems. Tech B says the flare shown was formed with an inverted flaring tool. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
D. The fitting shown is an ISO flare fitting. ISO flare fit tings are used on many newer vehicles, but should never be in termixed on the same vehicle with the more common inverted flare style fittings.

Tech A says the rest brake shoes should be properly adjusted before adjusting the parking brake. Tech B says the parking brake lever should be disengaged before adjusting the equalizer. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
A. The brake shoes must be correctly adjusted for the parking brake to work properly. There may not be enough adjustment in the parking brake system to overcome excessive shoe-to-drum clearance, resulting in the parking brake not being able to hold the vehicle in place when it is applied. Technician B is wrong because the parking brake lever must be engaged a certain number of clicks before the equalizer is adjusted.

Which of the following should be used to clean a disc brake rotor after it is machined?
A. compressed air
B. solvent tank
C. soap and water
D. brake cleaning solvent
C. When rotor resurfacing is completed, wash the rotor with soap and water and wipe it off with a clean shop towel. Brake cleaning solvent may not remove all of the fine particles left over from the machining process, and these can become imbedded in the new pads and cause brake noise.

A front brake hose is being replaced. On this type of hose, the male end threads directly into the caliper. Tech A says the end of the hose that attaches to the steel brake line should be connected first. Tech B says that a new copper sealing washer should be used when the hose is connected to the caliper. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
B. Technician A is wrong because the male end of the hose should be connected and tightened first. If the female end of the hose is connected to the brake line first, the hose will twist when it is threaded into the caliper.

Tech A says that surge bleeding is used in conjunction with manual or pressure bleeding. Tech B says that surge bleeding is used to remove air that is trapped in the brake hydraulic system. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
C. Surge bleeding is a method of removing air from the hydraulic system that can be used when manual or pressure bleeding has proved inadequate. Surge bleeding churns the air in the wheel cylinder in order to loosen any pockets of air. However, the system should first be manually or pressure bled and again after surge bleeding to make sure all air has been expelled.

All of the following are cause for brake rotor refinishing EXCEPT:
A. hard spots
B. heat checks
C. scoring
D. thickness variation
A. Hard spots call for rotor replacement, since resurfacing seldom removes the entire hard spot. All of the other conditions can be corrected by machining, provided it can be done without machining past the minimum rotor refinishing thickness.

In the above illustration, Tech A says that new brake shoes are being adjusted after installation. Tech B says that the procedure shown above is being done so the brake drum can be removed. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
B. The screwdriver shown in the illustration is not necessary when turning the star wheel to expand the brake shoes. However, if the shoes are too tight against the drum or a lip has developed due to wear that prevents the brake drum from being removed, the shoe-to-drum clearance must be reduced. To back off the star wheel adjustment, the screwdriver is used to hold the self-adjuster lever away from the wheel, allowing it to be turned in the opposite direction.

The front disc brake pads are being replaced on a vehicle with composite rotors. The left front rotor is scored below the ‘machine to’ but not the ‘discard’ thickness. The right front rotor has minor heat checks but otherwise checks out OK. If cast rotors are the only available replacements, which of the following is the proper course of action?
A. Machine both rotors, being careful not to exceed the ‘discard’ thickness.
B. Replace the left front rotor and machine the right front.
C. Replace both rotors.
D. Replace the left front rotor and leave the right front alone.
C. Composite and cast rotors should not be mixed on the same axle. Answer A is wrong because, as the question indicated, the rotor is already worn past the ‘machine to’ dimension. Even if the rotor is not machined beyond the ‘discard’ thickness, this leaves no allowance for wear in the future.

Which of the following brake symptoms can be caused by wheel bearing problems?
A. pedal pulsation
B. brake pull
C. grabbing
D. all of the above
D. Loose wheel bearings can cause excessive rotor runout, which in turn can cause pedal pulsation. A failed wheel bearing seal can allow grease to contaminate the brake linings and cause brake pull and grabbing.

Which component in the Hydo-Boost system provides power assist if there is a loss of hydraulic pressure to the system?
A. boost piston
B. check valve
C. accumulator
D. open-center spool valve
C. The accumulator can supply enough power assist for two stops if there is a loss of hydraulic pressure in the Hydro-Boost system. The boost piston provides the force to operate the master cylinder and the open- center spool valve regulates pump pressure. The check valve is used on vacuum operated boosters.

A customer complains that the parking brake will not keep his car stationary. The car has four-wheel disc brakes. Tech A says the caliper levers could be out of adjustment. Tech B says the brake shoes could need adjustment. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
C. The brakes must be inspected before reaching a diagnosis, but without knowing what type of system the car had, either technician could be right. There are two kinds of parking brakes on vehicles with rear disc brakes. One kind has small brake shoes inside a drum that is incorporated la the disc brake rotor. The shoes are forced against the drum by the linkage and cables in the same manner as conventional drum parking brakes. These shoes must be properly adjusted for the parking brake to work correctly. The other kind uses the rear disc brake pads. The linkage and cables actuate a cam or screw mechanism inside the caliper piston to push the caliper piston and pads against the rotor. Some of these systems require a caliper lever adjustment.

When replacing an integral hub/bearing assembly on a front wheel drive vehicle, all of the following must be removed EXCEPT:
A. brake rotor
B. brake caliper
C. steering knuckle
D. wheel
C. The steering knuckle doe s not have to be removed when replacing an integral hub/bear ing assembly. However, it must be removed when replacing the press-flt type front wheel bearing.

A wheel cylinder has been disassembled and corrosion and light scoring have been found in the bore. Tech A says the bore can be refinished using a small hone lubricated with cutting oil. Tech B says oversize pistons and cup seals can be installed if the hone removes too much material. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
D. Use only fresh clean brake fluid to lubricate the hon ing stones; never use petroleum-based cutting oil. After the cylinder has been honed, inspect it for excessive piston clear ance. To check the maximum clearance, place a 0.003-inch feeler shim lengthwise in the cylinder bore. If the piston can be inserted with the shim in place, the cylinder is oversize and cannot be rebuilt.

Two techs are discussing traction control systems. Tech A says that some traction control strategies do not use the brakes to control wheel spin. Tech B says that a fault in the ABS does not affect traction control. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
A. Some manufacturers reduce power to the spinning wheel by retarding the ignition timing, cutting off fuel injection to certain cylinders and/or mechani cally closing the throttle, and may only apply the brakes If the wheel continues to spin. Technician B is wrong because the TCS uses the same components as the ABS; if there is a fault in the ABS the TCS is turned off as well.

When rough machining a brake drum, the depth of cut and spindle feed rate should be:
A. 0.010-0.015-in. at high feed rate
B. 0.010-0.015-in. at low feed rate
C. 0.005-in. at high feed rate
D. 0.005-in. at low feed rate
A. The tool depth on a rough cut, where a large amount of material is removed to initially clean the drum, is usually about 0.010 – 0.015-in. at a fast spindle feed rate.

In the test show above, vacuum should:
A. exist on the engine side but not on the booster side
B. exist on the booster side but not on the engine side
C. exist on both sides
D. exist on neither side
B. The illustration shows a vacuum operated brake booster check valve being tested. Vacuum should exist at the booster side of the check valve, but not on the engine side.

Tech A says the number on the brake drum shown above indicates the maximum diameter, beyond which the drum should not be used. Tech B says the number indicates the maximum diameter the drum can be machined to. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
A. The number on the drum shown in the illustration is the maximum diameter. This specification is the discard diameter and not what the drum can be machined to. As a general rule, the maximum refinish diameter is 0.030-in. less than the maximum diameter, but refer to the vehicle service manual to be sure.

A vehicle’s brake warning system schematic is shown above. All of the following could cause the brake warning light to stay illuminated EXCEPT:
A. a short to ground between C105 and C201
B. a stuck closed parking brake switch
C. an open between C237 and C305
D. a leaking wheel cylinder
C. For the light to illuminate, the circuit must be grounded, either intentionally or unintentionally. Answer D Is an example of the former: a leak and loss of pressure in the brake hydraulic system causes the pressure differential switch contacts to close and complete the circuit. Answers A and B are examples of an unintentional ground: a short to ground or a switch that is stuck closed will still complete the circuit. Answer C is right because an open will not provide a ground and complete the circuit.

A tech wants to check the condition of a vehicle’s brake fluid. Where should he get the sample to make the most accurate determination?
A. master cylinder reservoir
B. brake caliper
C. combination valve
D. wheel cylinder
B. The most accurate way to determine brake fluid condition is to take a sample from the vehicle’s disc brake caliper, because the heat generated while stopping breaks down the corrosion inhibitors in the bake fluid.

Two techs are discussing brake bleeding procedures. Tech A says gravity bleeding is a relatively quick way to bleed a brake system. Tech B says silicone brake fluid cannot be gravity bled. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
D. Tech A is wrong because gravity bleeding is the easiest but most time consuming method of brake bleeding. Gravity bleeding relies on atmospheric pressure, acting on the surface of the fluid in the master cylinder, to force the fluid through the hydraulic system and out through the bleeders, which may take several hours. Tech B is wrong because gravity bleeding does not agitate the fluid and generate air bubbles, which is advantageous for systems with DOT 5 silicone-based fluid since it is prone to aeration.

Which of the following is the MOST cost-efficient method of correcting excessive lateral runout on a disc brake rotor?
A. indexing
B. shimming
C. machining
D. replacement
A. Indexing involves moving the rotor position on the hub and rechecking the runout with a dial indicator. The number of wheel studs determines the number of possible positions to correct runout. This method requires little extra labor, no parts expense and no machining labor or expense. Resurfacing the rotor unnecessarily removes material and makes the rotor thinner, lessening its ability to absorb and dissipate heat and shortening the rotor’s useable lifespan.

New disc brake pads have just been installed. Tech A says the new pads must undergo a burnishing process during the road test to ‘cure’ the pads. Tech B says the new pads must be burnished to seat them on the rotor. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
C. Whenever new brake pads are installed, they must undergo a burnishing, or break-in procedure before the vehicle can be operated normally. Burnishing accomplishes two things: It ‘cures’ the resin in the friction material, which could otherwise boil to the surface and cause glazing if the vehicle was immediately subjected to hard braking; and it ensures that the pads seat and make full contact with the rotor. The latter is particularly important if the rotors were not machined, since even a rotor that was deemed serviceable will not have a perfectly smooth surface.

The parking brake pedal on a vehicle with automatic parking brake release remains depressed when the vehicle is placed in drive. All of the following are possible causes EXCEPT:
A. defective vacuum motor
B. faulty release switch
C. vacuum leak
D. seized cables
D. An automatic parking brake release mechanism releases the parking brakes when the automatic transmission is shifted into drive or reverse. These systems usually consist of a vacuum motor that is attached to a release lever, and a vacuum switch that routes vacuum to the motor when the transmission is placed in drive or reverse. When the driver selects the drive or reverse position, the switch directs engine vacuum to the vacuum motor, which releases the lever and the parking brakes. Seized cables could keep the vehicle from moving or cause severe drag, but would not keep the pedal from returning to the unapplied position. All of the other possibilities listed could keep the release lever from releasing the pedal, causing it to remain in the applied position.

Two tech are discussing Electronic Stability Control (ESC) systems. Tech A says the ESC control module uses inputs from the steering wheel rotation sensor and wheel speed sensors to calculate the driver’s intended path. Tech B says the ESC control module uses inputs from the lateral acceleration and yaw rate sensors to calculate the vehicle’s actual path. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
C. The ESC control program determines the driver’s intentions using throttle and transmission data from the Powertrain Control Module (PCM), wheel speed rate from the wheel speed sensors and steering wheel position and rate of movement input from the steering wheel rotation sensor. It compares this information with the input from the lateral acceleration and yaw rate sensors to determine if correction is needed. If the actual path the vehicle is traveling does not match the intended path, the control module applies brake pressure to individual wheels and/or reduces engine power to correct the motion of the vehicle.

A vehicle exhibits intermittent ABS activation, but when the tech connects a scan too to the DLC, no DTS’s are found. Which of the following could be the cause?
A. damaged tone wheel teeth
B. loose wheel bearing
C. rust under the wheel speed sensor mount
D. all of the above
D. False ABS activation occurs when the ABS is engaged even though none of the wheels are slipping. The ABS control module can interpret a weak or erratic wheel speed sensor signal as wheel slip and cycle the ABS at the affected wheel. Rust under the sensor mount, loose wheel bearings and damaged tone wheel teeth can all affect the sensor gap, which in turn can cause a weak or erratic signal.

Tech A says as brake fluid ages, it can corrode ABS control valves. Tech B says brake fluid corrodes the copper in the brake lines. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
B. At a slow rate, over several months or years, brake fluid slowly corrodes the copper in the inner lining of steel brake tubing. The copper leaches into the brake fluid as ions, atoms with an electrical charge. When the corrosion inhibitors in the brake fluid eventually deplete, these copper ions become the oxidizer that corrodes ferrous metal parts like ABS control valves. Tech A is wrong because it is not the brake fluid that corrodes the ABS control valves, but rather the copper ions that are released b the brake fluid.

Which of the following is the MOST correct wheel cylinder repair procedure?
A. disassemble, loosen the bleeder screw, clean and hone, clean and assemble
B. disassemble, clean and hone, clean and assemble, loosen the bleeder screw
C. loosen the bleeder screw, disassemble, clean and hone, clean and assemble
D. disassemble, clean and hone, loosen the bleeder screw, clean and assemble
C. Before rebuilding a wheel cylinder, first make sure that the bleeder screw can be loosened before disassembling the unit. If the bleeder screw breaks off, the wheel cylinder must be replaced.

A vehicle’s ABS warning light is on and a DTC for the left front wheel speed sensor is found in the computer’s memory. When checked with an oscilloscope, the waveform for the left wheel speed sensor is erratic and uneven. Tech A says the sensor air gap is excessive. Tech B says the tone ring is probably damaged. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither
B. A tone ring with chipped or damaged teeth will cause an erratic, uneven waveform. Tech A is wrong because excessive air gap would cause a low amplitude waveform.

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