ok well i was driving to work today and i noticed my temp gauge go way up. and this like never happens so once i got to work i checked the coolant and it was like a gallon low. i filled it and it has been running at normal temperature. well i never see a puddle in the driveway so i had a bad feeling my problem was a head gasket but when i finally got around to pressure testing it i found coolant comming out from a small crack between the resivor and the radator fins. now that i made a short story long. i was wondering does it make sense that the coolant could be leaking so slow and only under pressure that it is evaporating before it puddles in the driveway? because when i pressure tested it the coolant didnt seap out but it bubbled out like when you put soap on a hole in a tire just little bubbles. and if i have to replace the radator is an aluminum one really that much better?