Coolant Overflowing and Leaking

i would also have the head gasket checked as you have probably cooked it

If the head gasket was damaged wouldn't it be leaking coolant as well? It doesn't seem to be leaking anywhere except for through that tube. I'm just trying to be hopeful that it's not actually the head gasket because that would mean I'd pretty much have to give the car up. I'll check my thermostat and cooling fan later today.

a head gasket can go between the bores check the condition of your oil if it has coolant in it it will be a light brown /cream colour on the filler cap and dipstick,9 times out of ten and changeing a head gasket is fairly simple on most vehicles especialy on v blocks if you are able to get the engine access and the gaskets to fit properly ergo dont go patent go genuine,

i had i problem similar to that and it turned out to be a pin hole in the radiator and after continuous driving is was pissing coolant out and causing the car to over heat. I found the problem by standing over the engine bay, and cranking the throttle cable and looking for signs of a leak. after my engine was warmed up and coolant was flowing i started to see coolant spit out at the top left corner of the radiator. Difficult to spot but examine the coolant system closely.

Did you ever find out what the tube was for? I have the same exact loose tube but my car isn’t overheating. It seems like it’s perfectly cut