Question 1

Two technicians are discussing master cylinders. Technician A says that it is normal to see fluid movement in the reservoir when the brake pedal is depressed. Technician B says a defective master cylinder can cause the brake pedal to slowly sink to the floor when depressed. Which technician is correct?

Accepted Answer

Both statements are correct. Fluid movement in the reservoir when the brake pedal is depressed is normal due to the displacement of brake fluid as the master cylinder pistons move. A defective master cylinder can indeed cause the brake pedal to slowly sink to the floor due to internal leaks within the cylinder, failing to maintain the necessary hydraulic pressure.

Question 2

If the brake pedal linkage is not adjusted correctly, brake fluid may not be able to expand back into the reservoir through the ________ of the master cylinder when the brakes get hot.

Accepted Answer

The vent port (forward hole) allows brake fluid to return to the reservoir when the brakes are released. If the brake pedal linkage is not adjusted correctly, this port may remain closed, preventing fluid expansion back into the reservoir.

Question 3

The primary brake circuit fails due to a leak in the lines, leaving the rear section of a dual split master cylinder. Technician A says that the driver will notice a lower than normal brake pedal and some reduced braking power. Technician B says that the brake pedal will "grab" higher than normal. Which technician is correct?

Accepted Answer

Technician A is correct because a leak in the brake lines of the primary brake circuit would result in a lower than normal brake pedal and reduced braking power, as part of the system's hydraulic pressure is lost. Technician B's statement about the brake pedal "grabbing" higher than normal is incorrect in this context; that might occur in other scenarios but not typically due to a leak in the brake lines.

Question 4

Two technicians are discussing a problem where the brake pedal travels too far before the vehicle starts to slow. Technician A says that the brakes may be out of adjustment. Technician B says that one circuit from the master cylinder may be leaking or defective. Which technician is correct?

Accepted Answer

Both technicians A and B are correct. A brake pedal traveling too far before the vehicle starts to slow can be caused by brakes being out of adjustment (Technician A's point) or by a leak or defect in one circuit from the master cylinder (Technician B's point).

Question 5

Air in the lines will cause what type of problem?

Accepted Answer

Air in the brake lines reduces the hydraulic pressure that can be generated within the brake system. This leads to a low or spongy brake pedal because the air compresses more easily than brake fluid, thus requiring more pedal travel to achieve the same braking effect.

Question 6

The master cylinder is able to move about how much brake fluid during each brake application?

Accepted Answer

The master cylinder typically moves about one teaspoon of brake fluid during each brake application, which is a small but effective amount for generating the necessary hydraulic pressure.

Question 7

Brake fluid pressure is measured in what unit?

Accepted Answer

Brake fluid pressure is measured in PSI, which stands for pounds per square inch.

Question 8

How much brake fluid is in a typical master cylinder reservoir?

Accepted Answer

The answer of How much brake fluid is in a...

Question 9

What part in the master cylinder helps keep air from contacting the brake fluid yet allows the fluid level to drop as the disc brakes wear?

Accepted Answer

The rubber diaphragm or floating disc in the master cylinder is designed to flex and move down as the brake fluid level drops (due to brake pad wear), while simultaneously preventing air from entering the system and contaminating the brake fluid.

Question 10

The brakes on a vehicle work OK for a while, then the vehicle slows because the brakes self-applied. Technician A says that an overfilled master cylinder could be the cause. Technician B says that a blocked vent port (compensating port) could be the cause. Which technician is correct?

Accepted Answer

Both technicians are correct. An overfilled master cylinder can cause hydraulic fluid to not have enough space to expand, leading to brake application. A blocked vent port prevents pressure from equalizing, also potentially causing brakes to self-apply.

Question 11

The rubber used in most brake system components will swell if exposed to ________.

Accepted Answer

Engine oil or ATF (Automatic Transmission Fluid) can cause the rubber used in brake system components to swell, leading to potential failure or malfunction of the brake system.

Question 12

Technician A says that the brake fluid reservoir should be filled to the top of the reservoir to be assured of proper brake pressure when the brakes are applied. Technician B says that the brake fluid level should be filled only to the maximum level line to allow for expansion when the brake fluid gets hot during normal operation. Which technician is correct?

Accepted Answer

Technician B is correct because brake fluid expands when it gets hot, and overfilling the reservoir can lead to leaks or damage to the brake system. Filling to the maximum level line allows for this expansion.

Question 13

Two technicians are discussing the operation of a dual master cylinder. Technician A says that the push rod is connected to the primary piston. Technician B says that the secondary piston is pushed forward by the fluid trapped ahead of the primary piston. Which technician is correct?

Accepted Answer

Both statements are correct. The push rod is indeed connected to the primary piston, and the secondary piston is pushed forward by the fluid trapped ahead of the primary piston in a dual master cylinder system.

Question 14

When cleaning hydraulic brake parts, use ________.

Accepted Answer

The answer of When cleaning hydraulic brake parts, use ________.
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Question 15

Brakes that drag or fail to release can be caused by a ________.

Accepted Answer

A plugged vent port (compensating port) can cause brakes to drag or fail to release because it prevents the brake fluid from returning to the master cylinder, keeping the brakes engaged.

Question 16

Technician A says that the primary seal of the secondary piston is leaking if fluid is seen leaking from the rear of the master cylinder. Technician B says that air in the brake lines will cause a low brake pedal. Which technician is correct?

Accepted Answer

The answer of Technician A says that the primary seal...

Question 17

Technician A says that if brake fluid movement is observed when the service brake is depressed, there is air in the hydraulic system. Technician B says that if venting (compensating) occurs, the master cylinder is usually operating okay. Which technician is correct?

Accepted Answer

Technician B is correct because venting (compensating) indicates that the master cylinder is functioning properly. Technician A is incorrect because brake fluid movement when the service brake is depressed does not necessarily indicate air in the hydraulic system; it could be normal fluid displacement.

Question 18

Self apply of the brakes can occur if ________.

Accepted Answer

The answer of Self apply of the brakes can occur...

Question 19

Technician A says that the brake pedal height should be checked as part of a thorough visual inspection of the brake system. Technician B says that the pedal free play and pedal reserve should be checked. Which technician is correct?

Accepted Answer

Both technicians are correct because checking the brake pedal height, pedal free play, and pedal reserve are all important parts of a thorough visual inspection of the brake system.

Question 20

Two technicians are discussing overhauling master brake cylinders. Technician A says that the manufacturer may recommend replacement of the entire master cylinder assembly instead of an overhaul. Technician B says that many overhaul kits include replacement piston assemblies. Which technician is correct?

Accepted Answer

Both statements by Technician A and Technician B are correct. Manufacturers may recommend replacing the entire master cylinder assembly for reliability or warranty reasons, and many overhaul kits do indeed include replacement piston assemblies as part of the components to ensure proper function after the overhaul.

Quiz 94: Brake Hydraulic Systems