When should the coolant level in a pressurized cooling system be checked?

The correct time to check the coolant level in a pressurized cooling system is when the engine is cold and not under pressure. Checking the coolant level ensures safety and accuracy, as the system can become pressurized and extremely hot while the engine is running or shortly after it has been turned off.

If the engine is hot, opening the coolant reservoir can cause hot coolant or steam to escape, potentially leading to burns. Therefore, the coolant should always be checked when the engine has cooled down, allowing for safe handling and accurate assessment of the coolant levels.

It's also advisable to check the coolant level regularly, not just during a maintenance check, to ensure that your cooling system is functioning properly and to avoid overheating during operation. Checking while driving or when the engine is hot is risky and not recommended for safety reasons.