well my girl crashed into someone like a month ago and messed up the front end. after a month ago there is smoke comeout from the radiator or around it. then the heater blows cold air. so i replace the thremostat and it worked fine for little bit. then again yesterday there was smoke coming around the radiator and now blows cold air again. can anyone tell me what could be the problem? thanks.

 

Its not the thermostat....i'd say you are losing coolant.
Any water under the car? the heater blowing cold means that you have air in the system, so the water is getting out somwhere.

 

Definitely a coolant leak. If that's a stock type radiator, the first thing I'd look for is signs the plastic end tanks are leaking where they meet the metal center section. That happened to me before.

 

its your radiator, she most likely cracked it.

 

If there is steam (smoke, water vapor) coming from the radiator; you either have a cracked endtank (common, especially after an accident involving the front end), a loose hose connection, or corroded tubes that are leaking.

Replacing the radiator/finding the leak is the first step.