Commercial Driver's License (General Knowledge) › Inspection
Under which of the following conditions is it safe to remove the radiator cap on your vehicle?
The entire engine system is completely cooled
The radiator is undamaged and the engine is warm
The engine is not overheated, but the engine has been in recent use
None of these; the radiator cap should never be removed
In order for it to be remotely safe to remove your radiator cap, the entire engine system must be completely cooled. Even in that condition, removing the radiator cap should be only be done with extreme caution.