Replace the pressure relief valve.
The overflow tank is either cracked or its overheating and leaking from the cap
check to see if the overflow bottle cap is in 2 parts allowing antifreese to escape the overflow tank system when the engine is running your car might also be running cold all the time even though the overflow tank shows full
adjust the floating bulb, it may be running over the top of the overflow pipe
It could be the coolant overflow tank that is leaking.
Either the flapper in the bottom of the tank is leaking or the water level is too high and it is running down the overflow tube.
Temp. & pressure valve either needs replaced or an expansion tank may need to be installed.
To avoid any overflow
If it is leaking out of the bottom, you replace it. There is no way to patch a leak in a water heater.
A gas tank can indeed overflow if it is not full. A gas tank can overflow if the pressure inside of it is too high.
Are you sure where the water is coming from? (1) Could it be A/C condensation draining from condensate collector pan? (2) Could it be overflow from the radiator overflow tank? (3) Could it be leaking from the water pump (which could possibly signify imminent failure of the pump)? If you can answer all thes questions in the negative - then take it back to whoever did your gasket work and ask THEM.
An overflow is a box that hangs on the back of the tank (or is sometimes built in) and allows the water to "overflow" to a wet/dry filter (the tank sized filters people have underneath their tanks). The overflow has a U shaped tube that allows water to siphon from the main tank into the overflow box. The overflow box then drains the water down a tube to the wet/dry filter continuing the siphon by pulling the water as it drains. If you are going to purchase on, they should come with instructions. www.wetwebmedia.com is a good place to learn about all types of fish related things.
if your water/antifreeze gets to hot it pushes out the over flow tube into the overflow container, as it cools down it will suck it out of the overflow and back into the radiator.