Answer
There is high pressure under the cap when the coolant is hot and it can and will burn you,\ if the cap is opened. Never open the main radiator cap when the engine is hot, especially if it was overheating.
Work Step by Step
There is high pressure under the cap when the coolant is hot and it can and will burn you if the cap is opened. Never open the main radiator cap when the engine is hot, especially if it was overheating.