2001 chevy blazer 2wd LT.

i noticed the heater was not getting as hot as it should, a few minutes later the temp went up to around 240. when i got home i topped off the radiator with about a gallon of water. over the last 3 days i have to add a gallon a day. i have not seen any leaks. oil looks fine. i see a bit of moisture coming from the exhaust pipe. alsmost a constant drip. one every 5 seconds or so. blown intake or head seal?

 

Check pass.floor for wetness...Heater core bad??

 

its dry. wife went to store tonight and came back to find puddle under engine. i will check location tomorrow. thanks.