Which of the following factors may result in decrease in the level of the cooling system liquid?

In the photo you can see the engine compartment of a tractor with the bonnet raised: a white coolant expansion tank with a yellow cap next to the air filter housing. A drop in the fluid level in the cooling system can be caused by a leak in the system - answer B.

The cooling system is closed, so in a properly working engine the amount of fluid practically does not go down. If the level drops, it is usually because of a leak: a cracked hose, a loose clip, or a leaking radiator, water pump or cylinder head gasket. The engine running at high revs (answer A) does not in itself cause any loss of fluid. A damaged water pump drive belt (answer C) will make the fluid stop circulating, and the engine will quickly overheat, but the fluid level will not drop immediately. When fluid is going down, you look for a leak - wet patches under the tractor, stains on the hoses - and you top up fluid of the correct type only when the engine is cold.

Legal basis: Art. 66 para. 1 point 1 of the Road Traffic Act (Prawo o ruchu drogowym)