I have a 98 honda accord, and while driving the car home from work i notice the air conditioner stop blowing cold air and starting blowing rather warm air then i notice the temperature hand was on the "H" (hot) so i pulled over and steam was coming from under the hood. So i waited awhile and add water to the radiator then after 15-30 minutes it was around normal again. This has happen twice, once with me and once with my mother-in-law.

benn11

Why don't you take for service? Because it seems like it might need professional attention! Don't let it continue for a long period because it might cause major problem.

svizzini

Steam coming from under the hood usually means a leak. The cooling system is a closed system. It should never leak at all or need to have water added periodically. Take it to a garage for a cooling system pressure test. It will find all leaks, if any.

As for waiting 15 minutes and adding water, the proper way to add water is always with the motor running. Do not add water if the motor is not running. Once you have the radiator cap off, start the engine and add water as required.

Removing the radiator cap for an overheated engine is dangerous. Be careful. Squeeze the upper radiator hose to check for pressure. If there is pressure and the engine is hot, do not remove the radiator cap -- unless you understand the risks. Being scalded by steam from a hot engine can put you in the hospital or blind you. Don't mess with it if you don't understand what you're doing. Just wait until it cools down. (Sounds like that's what you did.)

If you added water, the fluid in the cooling system is no longer a 50-50 mix of coolant and water. You must service the cooling system with a fresh mix of coolant and water in the proper ratio. If you do not, the diluted coolant will no longer be able to inhibit the formation of rust and your cooling system will slowly rust to death. Long term, this can be an expensive problem. Don't let it happen.