boiling overflow tank

[kewlcoconut]

this was pretty weird tonight when i came home from school. i pulled up into my driveway and parked and shut the car off. when i got out, i heard weird noises, and i noticed some steam coming out of the hood.....I was like "omg what now!"

i popped the hood and the radiator overflow tank was boiling over like crazy. i lost a lot of fluid from the radiator. it was just pouring out and spitting all over the front of the radiator. I dont know what happened. this was such a spur of the moment thing.
my temp sensor hasnt worked for a few weeks but the car hasnt had any issues. Im getting my temp sensor replaced tomorrow, along with a bunch of tests run.

it is odd though, because this has never ever happened. and i dont know what could have caused this. I noticed though that my heater wasnt really working, it usually heats up way before i am home. could it have gotten clogged or something? and pushed the excess coolant back? i dont know, im just thinking of random stuff.........some input would be nice. thanks guys