CSLB General Building (B) — All Questions

A brake pedal that slowly sinks to the floor while held under steady pressure most likely indicates:

• a.Air in the lines only
• b.Warped rotors
• c.A failing master cylinder (internal leak)✓
• d.Glazed brake pads

A pedal that gradually falls under steady pressure indicates fluid bypassing internally in the master cylinder past worn seals. An external leak would lose fluid visibly. Replacing the master cylinder and bleeding the system restores a firm pedal.

Technician A says a spongy brake pedal is commonly caused by air in the hydraulic system. Technician B says air in the lines increases braking power. Who is correct?

• a.Technician A only✓
• b.Both A and B
• c.Technician B only
• d.Neither A nor B

Air is compressible, so it makes the pedal feel soft or spongy and reduces braking effectiveness; proper bleeding removes it. Technician B is wrong because air degrades rather than improves braking. Bleeding in the correct sequence restores a firm pedal.

Technician A says a pulsating brake pedal is usually caused by air in the hydraulic lines. Technician B says it is usually caused by rotor thickness variation or excessive lateral runout. Who is correct?

• a.Technician A only
• b.Technician B only✓
• c.Both A and B
• d.Neither A nor B

Thickness variation or warp causes the pads to move in and out as the disc turns, producing a pulsation felt in the pedal, while air produces a soft pedal instead. Technician B is correct. Measuring runout and thickness variation confirms it.

The primary purpose of a brake power booster is to:

• a.Store brake fluid
• b.Adjust the parking brake
• c.Prevent wheel lockup
• d.Reduce the pedal effort required to apply the brakes✓

The vacuum or hydraulic booster multiplies the driver's pedal force so less effort is needed for firm braking. A failed vacuum booster or leaking check valve produces a hard pedal. It works with, not instead of, the hydraulic system.

The main function of an anti-lock brake system (ABS) is to:

• a.Increase brake fluid pressure permanently
• b.Replace the parking brake
• c.Prevent wheel lockup and maintain steering control during hard braking✓
• d.Eliminate the need for brake pads

ABS pulses hydraulic pressure to keep wheels from locking so the driver retains steering control and shortens stopping distance on most surfaces. Wheel-speed sensors feed the control module, which modulates the hydraulic unit. A fault typically turns on the ABS warning lamp and disables the function.

A wheel-speed sensor signal that is missing on one wheel will most likely cause the ABS to:

• a.Increase engine power
• b.Set a code and disable ABS, reverting to normal braking✓
• c.Lock all four wheels
• d.Apply the parking brake

A lost wheel-speed signal sets a DTC and usually disables ABS, leaving conventional (non-anti-lock) braking available. The ABS warning lamp illuminates. Common causes include a damaged sensor, wiring, or a contaminated tone ring.

Brake fluid is hygroscopic, which means it:

• a.Absorbs moisture from the air over time✓
• b.Repels all water
• c.Conducts electricity
• d.Expands when frozen

Glycol-based brake fluid absorbs moisture, which lowers its boiling point and can cause corrosion and a spongy pedal from vapor under heavy braking. This is why periodic fluid replacement is recommended. Sealed containers and prompt cap replacement limit moisture uptake.

During a disc brake job, a technician should measure rotor thickness and compare it to the:

• a.Tire pressure specification
• b.Battery voltage
• c.Toe specification
• d.Minimum (discard) thickness stamped on the rotor✓

Rotors must remain above the minimum thickness (often cast or stamped on the rotor) to dissipate heat and resist warping. A rotor below spec must be replaced, not machined. Measuring with a micrometer at several points also reveals thickness variation.

Technician A says brake shoes are used in disc brakes. Technician B says brake shoes are used in drum brakes. Who is correct?

• a.Technician A only
• b.Technician B only✓
• c.Both A and B
• d.Neither A nor B

Drum brakes use curved shoes that press outward against the drum, while disc brakes use flat pads that clamp a rotor. Technician B is correct. Many vehicles combine front discs with rear drums or discs.

Technician A says a grinding, metal-on-metal noise during braking indicates friction material worn past its limit. Technician B says continued driving in that condition can score the rotor or drum. Who is correct?

• a.Both A and B✓
• b.Technician A only
• c.Technician B only
• d.Neither A nor B

When friction material wears away, the metal backing contacts the rotor or drum, producing a grinding noise, and continued driving scores the surface and raises repair cost. Both technicians are correct. Immediate pad or shoe replacement and surface inspection are required.

A rear disc parking brake that will not hold is often caused by:

• a.A misadjusted or seized parking brake mechanism/cable✓
• b.Air in the front lines
• c.A failed wheel-speed sensor
• d.Low battery voltage

Parking brake holding faults usually trace to cable stretch, misadjustment, or a seized caliper parking mechanism. Proper adjustment and lubrication restore holding force. On integral rear calipers, the internal actuator must function for both service and parking braking.

A brake caliper that sticks and does not release will most likely cause:

• a.A soft pedal only
• b.Dragging, overheating, and pulling to that side✓
• c.Loss of all braking
• d.A hard pedal at all times

A seized caliper keeps the pads applied, causing drag, excessive heat, uneven pad wear, and a pull toward that wheel. Overheated fluid can boil and reduce braking. Rebuilding or replacing the caliper and inspecting the slides and hose corrects it.

The metering valve in a combination valve is used to:

• a.Increase rear brake pressure
• b.Warn of ABS faults
• c.Bleed the master cylinder
• d.Delay front disc application so rear drums engage together✓

The metering valve holds off front disc pressure briefly so the rear drum shoes overcome their return springs and apply at nearly the same time, balancing braking. The proportioning section limits rear pressure to prevent lockup. Together these balance front-to-rear braking.

When bleeding a conventional hydraulic brake system, the general rule is to bleed:

• a.All wheels at the same time
• b.Only the front wheels
• c.Starting at the wheel nearest the master cylinder✓
• d.In the sequence specified by the manufacturer, often longest line first

Manufacturers specify a bleeding sequence, frequently starting at the wheel farthest from the master cylinder, to purge air effectively. Following the correct order and keeping the reservoir full prevents introducing more air. Some ABS units require a scan tool to bleed fully.

A proportioning valve in the brake system is designed to:

• a.Reduce pressure to the rear brakes to prevent early lockup✓
• b.Increase pressure to the front only
• c.Store extra brake fluid
• d.Operate the parking brake

Because weight shifts forward during braking, the proportioning valve limits rear brake pressure to keep the rear wheels from locking prematurely. This maintains stability during hard stops. Many vehicles now handle this function electronically through ABS/EBD.

Technician A says silicone (DOT 5) and glycol (DOT 3/4) brake fluids can be freely mixed. Technician B says brake fluid type is unimportant. Who is correct?

• a.Technician A only
• b.Technician B only
• c.Both A and B
• d.Neither A nor B✓

Silicone and glycol fluids are not compatible and must not be mixed, and using the wrong fluid type can damage seals and reduce performance. Both technicians are incorrect. Always use the fluid specification listed for the vehicle.