You should never open your radiator pressure cap or coolant overflow bottle when your engine is hot. Hot coolant and steam can cause severe burns. Check your owner's manual, or ask you service advisor about when you should have your coolant replaced. At 1 STOP Tire & Auto Service in Castle Rock we install quality NAPA replacement parts. Give us a call at 303.688.0366 and let us help keep you safely and economically on the road.