I have a 99 Altima. Was driving one day and the belt broke. when the belt broke it also broke the alternator pulley and idler pulley. I replace both belts, the alternator and the idler pullet. I took it for a test drive and the car overheated, and the Radiator busted. I also notice the sensor near the alternator on on the upper radiator hose was broken. so i replaced it. then i put everything back and started the car and noticed smoke coming from the top of the engine and near the header. the fans also came on after 15 mins. So I replaced the thermostat. still the same. I tried flushing the coolant from the radiator and try to bleed it. still the same. I am not sure what to do next. what else could be wrong? please help!.

if the coolent is low after running the car check the radiator cap, might be bad(lets coolant out but not back in)

Its not low. I did replace the cap when I replaced the radiator

head gasket?