UH OH, i had this same problem with my car, I would drive and all the sudden the upper radiator hose would pop off, coolant everywhere. here is what I would have checked out

1. If u havn't done so alreay, replace the thermostat housing with the upgraded metal one for better fitting.
2. Check upper radiator neck for cracks or completely broken,
3. Have the water pump checked out...Mine started leaking from taking too long to repair the radiator.
4. Be sure to have all your radiator hoses replaced when getting the radiator done
5. One last thing, refill it with MB Coolant


I never really knew what went first, the radiator or the water pump, but i'd just get them both checked out...Soryy to say this cost me a total of around 1100, and ALOT of frustration
Good Luck