I just recently replaced a tube connecting my water heater core to my water pump.. My car ran good after that for a couple days. Now today, out of no where, my car shot a whole bunch of coolant out of what looks like an overflow valve next to my radiator cap. Now it's running hot. Hopefully there are just bubbles in my cooling system.. HELP

 

Thermostat?

 

If it's running hot then it's not not circulating or it's really low(which I doubt). I would double check whatever you did and make sure you didn't block or pinch something shut.