You may have a bad radiator cap.
The overflow tank is either cracked or its overheating and leaking from the cap
It could be the coolant overflow tank that is leaking.
The overflow bottle may overflow if: 1. The car is overheating - this means after the coolant in the radiator gets heated up and expands it flows to the reserve bottle but the radiator doesn't cool down to suck back the coolant from the overflow bottle, but just keeps on sending coolant to the bottle. 2. You may have put excess coolant in the bottle - hence heated coolant from the radiator didn't get enough space.
Bad head gasket? Bad thermostat? Defective radiator cap?
maybe not. check engine oil for color and quantity. if oil is white to grey, then there is coolant leaking into engine.no pressure might be caused by bad radiator cap.this will also allow coolant to escape
Could be thermostat not opening causing a back pressure
Only if the coolant is leaking from the heater core, but you will see this.
sounds like someone hooked the coolant overflow hose up the windshield reservoir tank lol.
The heater is leaking coolant.
The excess drained out of the overflow until it was down to the level it should be...
You probably have a bad heater core. The heater core is installed in a plastic casing and the spout is there in case it starts leaking. This keeps it from leaking into the floor of the car.
Coolant is old.