Breaking down on the side of a road due to an overheating engine is every driver's worst nightmare. While towing your car for repairs may seem like the only option, a quick short-term fix can get you back on the road in no time. Pouring water into the coolant tank will allow the water to temporarily act as a coolant for the engine. This should allow for enough time to drive to a shop to diagnose the full problem.
Pull over your overheated vehicle and turn it off. Wait for an hour or so for the coolant to cool.
Wrap a cloth around the upper radiator tube and attempt to squeeze it. If you can't easily squeeze the radiator tube, wait longer for the car to cool.
Wrap a cloth around the radiator cap. Release the pressure very slowly and carefully. Many have been burned doing this, so wait longer if you're not willing to take the risk.
Turn the car back on once you have removed the radiator cap. Slowly pour water into the coolant tank until the car is running at a safe driving temperature.
Screw the radiator cap back on very slowly until it is tight.
Drive to the nearest mechanic to diagnose the full problem. Typically the problem can be solved by replacing the coolant fluid, although it could be a host of other issues.
