Question 1: After a brake pedal release, the left rear wheel continues to drag. Loosening the left rear bleeder lets a spurt of fluid escape, and the drag disappears. Which is the most likely cause?

• A seized rear wheel cylinder piston
• An out-of-adjustment parking brake cable
• A collapsed inner liner in the flexible rear brake hose (Correct answer)
• A stuck open metering valve

Correct answer: A collapsed inner liner in the flexible rear brake hose

A deteriorated hose liner can act as a one-way valve, trapping pressure at the wheel after the pedal is released. Opening the bleeder relieves the trapped pressure and frees the brake.

Flexible brake hoses can fail internally while looking fine outside. A torn or swollen inner liner can flap like a check valve. Fluid can then pass toward the wheel under pedal pressure but cannot return when the pedal is released. The brake stays applied until pressure is vented at the bleeder. Replace the hose in pairs on an axle when practical, and bleed the system afterward.

Question 2: Which is the main purpose of the metering valve in a front disc/rear drum brake system?

• To delay front brake application until the rear shoes have overcome their return springs (Correct answer)
• To limit rear brake pressure during hard stops
• To turn on the dash warning lamp when one circuit loses pressure
• To adjust rear pressure according to vehicle ride height

Correct answer: To delay front brake application until the rear shoes have overcome their return springs

The metering valve briefly holds off pressure to the front disc brakes so the rear drum shoes can begin to move. This gives more balanced application at low pedal pressure.

Drum brake shoes must first overcome return spring tension before they contact the drum. Disc pads need very little pressure to make contact. Without a metering valve, the front brakes could apply first at light pedal effort, which causes a nose-dive feel. The metering valve holds back front pressure for a short interval, then opens fully. It acts mostly at low pressures and has no effect during hard braking.

Question 3: A technician is replacing a section of steel brake line on a vehicle that uses SAE 45-degree flare fittings. Which type of flare should be formed on the tube end?

• A single flare, because it seals best against the seat
• A flat-ended compression flare
• A beaded flare with no fitting nut
• A double flare (Correct answer)

Correct answer: A double flare

SAE 45-degree brake fittings require a double flare. The doubled-over wall is stronger and resists splitting under high pressure.

A single flare thins and weakens the tube end, so it can crack under brake pressure and vibration. A double flare folds the end back to form a two-layer wall that seats against the fitting and seals. Some vehicles use ISO (bubble) flares instead, which are not interchangeable with 45-degree double flares. Always match the flare type to the fitting and inspect it for cracks before assembly.

Question 4: Which is the main purpose of a proportioning valve in a brake system?

• To keep the brake lines filled with fluid when the pedal is released
• To reduce the rate of pressure increase to the rear brakes during heavy braking (Correct answer)
• To sense a pressure imbalance between the two hydraulic circuits
• To delay the application of the rear brakes at low pressure

Correct answer: To reduce the rate of pressure increase to the rear brakes during heavy braking

During hard braking, weight shifts forward and the rear wheels unload. The proportioning valve limits the rise in rear pressure so the rear wheels do not lock prematurely.

Under hard braking, vehicle weight shifts to the front axle and rear traction decreases. If the rear brakes received the same pressure as the front, they would lock early and the vehicle could become unstable. A proportioning valve passes full pressure up to its split point. Above that point it lets rear pressure increase at a reduced rate. This keeps front and rear braking force closer to the available traction.

Question 5: What causes the red brake warning lamp to light through a pressure differential switch?

• A drop in hydraulic pressure in one circuit shifts the valve piston into contact with the switch (Correct answer)
• Fluid pressure rising above the proportioning valve split point
• The metering valve opening fully at high line pressure
• Both circuits having equal pressure after a brake application

Correct answer: A drop in hydraulic pressure in one circuit shifts the valve piston into contact with the switch

If one circuit loses pressure, the higher pressure in the other circuit pushes the differential piston toward the low-pressure side. The piston closes the switch and lights the warning lamp.

A pressure differential valve has a piston balanced between the two hydraulic circuits. When both circuits have equal pressure, the piston stays centered. A leak in one circuit lowers the pressure on that side, so the good circuit pushes the piston off center. The piston ramp then contacts the switch plunger and completes the warning lamp circuit. The lamp warns the driver that only part of the system is working.

Question 6: A technician installs a gauge in the front line and another in the rear line to test a combination valve's proportioning function. What should the gauges show when pedal pressure is well above the valve's split point?

• Rear pressure equal to front pressure
• Rear pressure rising more slowly than front pressure (Correct answer)
• Rear pressure higher than front pressure
• Rear pressure at zero

Correct answer: Rear pressure rising more slowly than front pressure

Above the split point, a working proportioning valve reduces the rate of rear pressure rise, so rear pressure falls progressively below front pressure.

Below the split point, front and rear pressures should be about equal. Above it, the valve allows rear pressure to rise only a fraction of the front pressure increase. Comparing the two gauge readings against the manufacturer's specifications shows whether the valve works. If rear pressure equals front pressure well above the split point, the valve is not proportioning and should be replaced. Do not try to repair these valves.

Question 7: Why is copper tubing not acceptable for replacing a steel brake line?

• It cannot be flared with standard tools
• It expands too much when heated by the brakes
• It reacts chemically with DOT 3 brake fluid
• It work-hardens and cracks from vibration, and it cannot safely withstand brake system pressures (Correct answer)

Correct answer: It work-hardens and cracks from vibration, and it cannot safely withstand brake system pressures

Copper work-hardens with vibration and flexing, which leads to cracking and leaks. It also lacks the strength needed for brake pressures.

Brake lines must handle very high pressure while enduring constant vibration. Copper fatigues and hardens as it flexes, so it can fracture without warning. Approved replacement lines are double-walled, steel tubing with a corrosion-resistant coating, or other approved alloys such as copper-nickel. Use only tubing made for brake systems and correct flare fittings. Never use plumbing or fuel line tubing.

Question 8: After installing a new front brake hose, what check should be made before returning the vehicle to service?

• Measure hose length against the old hose with the vehicle on a lift
• Turn the steering wheel fully left and right and check for hose binding, stretching, or contact (Correct answer)
• Pressurize the hose to 5,000 psi with the engine off
• Twist the hose one quarter turn to relieve stress on the fittings

Correct answer: Turn the steering wheel fully left and right and check for hose binding, stretching, or contact

Steering and suspension movement must not stretch, kink or rub the hose. Turning lock to lock confirms there is enough slack and clearance.

Front brake hoses move with both steering and suspension travel. A hose that is too short, twisted, or routed incorrectly can stretch or rub through when the wheel is turned. After installation, check the hose with the wheels at full lock each way and during suspension movement. The hose should not twist. Many hoses have a stripe along their length to help verify there is no twist.

Question 9: A technician needs to loosen a corroded brake line fitting at a wheel cylinder. Which tool is the best choice to reduce the risk of rounding the fitting?

• Adjustable wrench
• Flare-nut (line) wrench (Correct answer)
• Locking pliers
• Open-end wrench

Correct answer: Flare-nut (line) wrench

A flare-nut wrench grips most of the fitting's flats, which spreads force and helps prevent rounding the soft fitting nut.

Brake line fitting nuts are made of relatively soft metal and corrode easily. Open-end wrenches, adjustable wrenches and pliers grip only part of the nut and can round the corners. A flare-nut wrench has a nearly closed jaw that contacts most of the flats while still sliding over the tube. Applying penetrating oil and careful turning also help prevent line damage. Support the line to keep it from twisting.

Question 10: A pickup with a height-sensing proportioning valve has its rear wheels lock up early under hard braking when the truck is lightly loaded. Which is the most likely cause?

• A leaking primary piston seal in the master cylinder
• Worn rear brake shoe linings
• A seized valve linkage or a misadjusted valve that holds it in the loaded position (Correct answer)
• A failed pressure differential switch

Correct answer: A seized valve linkage or a misadjusted valve that holds it in the loaded position

A height-sensing valve should reduce rear pressure when the vehicle is lightly loaded. If the linkage is stuck or misadjusted as if loaded, rear pressure stays too high and the rear wheels lock early.

A load-sensing or height-sensing proportioning valve changes the rear brake pressure according to how much weight is on the rear axle. A lightly loaded truck needs less rear pressure because the rear tires have less traction. If the linkage is bent, stuck or incorrectly adjusted, the valve behaves as though the truck is heavily loaded. The result is too much rear pressure and premature rear lockup. Check linkage condition and adjustment against the manufacturer's procedure.

Question 11: A technician finds a brake hose that appears swollen along part of its length when the brake pedal is firmly applied. What action is correct?

• Replace the hose (Correct answer)
• Wrap the area with tape and recheck in a month
• Tighten the hose end fitting a quarter turn
• Bleed the line until the bulge disappears

Correct answer: Replace the hose

A bulge means the reinforcing layers have failed and the hose could burst. The hose must be replaced.