How should the coolant level be checked in a bus?

The correct method for checking the coolant level in a bus is by pushing the pressure relief valve and checking the level. This method ensures that the system is under safe pressure conditions, allowing for an accurate reading of the coolant level without risking injury or damage to the system. Pressurizing the cooling system can alter the coolant level, so utilizing the pressure relief valve allows for proper assessment while ensuring safety protocols are met.

Using a dipstick is typically not a standard method for checking coolant levels in bus systems, as these systems do not generally employ dipstick measurements. Observing the color of the coolant can provide information about its condition but not necessarily its level. Additionally, opening the radiator cap directly to inspect the coolant level can be hazardous if the system is hot and pressurized, posing a risk of burns or injury. Hence, utilizing the pressure relief valve is both a safe and effective means of accurately checking coolant levels.