49.20. The level of coolant in the expansion tank is below normal, and its density is above normal, which indicates:
UAРівень охолоджуючої рідини в розширювальному бачку нижче норми, а її щільність вище норми, що вказує:
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This exam question focuses on the technical condition of the vehicle and the prevention of malfunctions that directly affect road safety. Although the Traffic Rules of Ukraine mainly regulate driver behavior on the road, the theoretical exam often tests basic knowledge of vehicle operation: engine overheating, cooling system failure, or sudden loss of fluid can lead to stopping in a dangerous place and create an accident risk.
In essence, this task does not relate to specific provisions of the traffic rules, but to the topic "Technical condition and operation of vehicles" within the exam preparation. The logic is simple: the level in the tank indicates a loss of volume, and the density reflects the concentration of the antifreeze and water mixture. If the level is below normal but the density has increased, this means that mainly water has "gone" (it evaporates faster), and the mixture has become more concentrated—a typical sign of boiling during overheating.
The option about external leakage is not suitable, because when the system leaks, the ready-made mixture usually escapes in an unchanged proportion, so the density should not increase. The wording about external or internal leakage is also less accurate for the combination "low level + increased density," since this picture is more characteristic of the evaporation of the water part during boiling. The practical conclusion for the driver: after the engine cools down, restore the level (often with distilled water to return the density to normal) and be sure to find the cause of the overheating to avoid recurrence of the problem on the road.
The relevant specific clauses of the Traffic Rules of Ukraine are absent
The Traffic Rules of Ukraine do not contain standards that define or describe the diagnostics of the condition of the coolant (level in the expansion tank, “coolant density,” signs of “boiling,” etc.), nor do they establish a cause-and-effect relationship between a decrease in level and an increase in coolant density.
This exam question tests knowledge of technical operation/maintenance of the vehicle (engine cooling system), rather than knowledge of specific provisions of the Traffic Rules.
Thus, the correct answer is "Indicates coolant boiling," given that by the definition of the Traffic Rules, the issue of coolant density/level and their interpretation is not regulated by the Rules and belongs to technical knowledge about the operation of the cooling system.
Two indicators are monitored in the cooling system: the level in the expansion tank and the density of the coolant. The level shows how much fluid actually remains in the system, while the density reflects its concentration (the ratio of antifreeze to water).
If the level is below normal, it means that some of the fluid has disappeared from the system. Next, it is important to look at the density: in this question, it is higher than normal, meaning the mixture has become more concentrated. This happens when mainly water, not the antifreeze component, leaves the fluid. The most typical reason for this in real operating conditions is overheating and boiling, when water evaporates faster than the antifreeze components. As a result, the volume decreases and the density increases.
For comparison: if the level dropped due to a lack of tightness (leakage of hoses, radiator, etc.), the fluid would leak out as a mixture in the same composition, and the density usually would not become higher than normal. That is why the combination of "low level + increased density" logically indicates not a usual leak, but the loss of the water part due to boiling.
The practical conclusion from such a sign is simple: the density increased due to water evaporation, so to return the indicators to normal, distilled water is usually added, and it is essential to find out the cause of overheating so that the situation does not recur.
Therefore, the correct answer is "Due to fluid boiling," because a decrease in level together with an increase in density means that mainly water has evaporated from the mixture, and the fluid has become more concentrated.