Braking Systems Questions and Answers

Answer: A

Glycol fluid is hygroscopic and typically absorbs around three per cent water in two years, which lowers the boiling point drastically. That is why renewal is specified by time rather than mileage. Silicone fluid does not absorb water but has other drawbacks. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision. Naming what changes and what stays the same is the reliable route through questions of this shape.

Answer: B

Specifications quote a dry boiling point for fresh fluid and a wet one for fluid containing three and a half per cent water, and the wet figure is far lower. The distinction inverts the second option. A refractometer or an electronic tester measures the condition. Reading the definition literally, rather than recalling a summary, avoids the usual confusion. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb.

Answer: C

Glycol fluid attacks paint immediately and the damage is permanent, so spills are flushed with water at once. Silicone fluid does not. It is the reason a cloth is placed beneath the master cylinder before topping up. Most errors here come from carrying across a result from a neighbouring case where it does not hold. A symptom that appears under one condition and not another is what narrows the diagnosis quickly. Reading the definition literally, rather than recalling a summary, avoids the usual confusion.

Answer: D

Mineral oil swells and destroys the rubber seals throughout the system, requiring every component to be replaced. Mixing DOT grades of glycol fluid is acceptable. Silicone is a separate incompatibility but the classic and catastrophic error is mineral oil. Naming what changes and what stays the same is the reliable route through questions of this shape. The order in which the effects act is what decides the outcome, so it is worth establishing first.

Answer: A

Every rubber component that has contacted the oil is swollen and must be replaced, which usually means the whole system. Flushing does not reverse the swelling. It is an expensive lesson in reading the label. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb. Checking which component actually carries the load settles most questions of this kind at once. Most errors here come from carrying across a result from a neighbouring case where it does not hold.

Answer: B

Air is compressible, so any trapped in the system produces a spongy pedal and reduced effectiveness. Water is removed by a fluid change rather than by bleeding, although the operations use the same equipment. The distinction is worth keeping. A symptom that appears under one condition and not another is what narrows the diagnosis quickly. The shared behaviour explains why these belong together and the differences explain why both exist. Framing the question as which quantity the change acts upon makes the answer follow without calculation.

Answer: C

Working from the furthest wheel inward is the traditional order, though many manufacturers specify a particular sequence for their system. The manufacturer's order always takes precedence, especially where anti-lock components are involved. The order in which the effects act is what decides the outcome, so it is worth establishing first. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision.

Answer: D

If the reservoir empties, air enters the master cylinder and the whole operation begins again. The engine is normally off so the servo does not interfere. Bleed screws are opened only part of a turn. Checking which component actually carries the load settles most questions of this kind at once. Reading the definition literally, rather than recalling a summary, avoids the usual confusion. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb.

Answer: A

A pressure bleeder pressurises the reservoir so fluid flows continuously and the reservoir cannot empty. A vacuum bleeder draws rather than pushes, so the second option inverts the mechanism. Pedal bleeding works but needs two people. Tracing the requirement back to the physical constraint that produces it makes the answer follow. Most errors here come from carrying across a result from a neighbouring case where it does not hold. Reading the definition literally, rather than recalling a formula, is the reliable route through questions of this shape.

Answer: B

Air trapped in the modulator cannot be expelled by pedal pressure alone, so a scan tool cycles the valves and the pump during bleeding. Omitting the step leaves a permanently spongy pedal. Accumulators do need depressurising on some systems, which makes that option plausible. The shared behaviour explains why these belong together and the differences explain why both exist. Naming what changes and what stays the same is the reliable route through questions of this shape.