White steam/; smoke coming out of tail pipe. There is quite alot of it at idle. Engine is 3.7 liter v-6. New radiator, water pump, and fan clutch. Got engine code p0300. Was looking for EGR valve since engine wants to idle rough when stopped at lights and such. Noticed that radiator was about 3/4 gallon low. Added some 50/50 to it and wife noticed the smoke/steam coming out of exhaust. Smelled like hot anti freeze. Walked back to radiator and noticed fluid level was down about 3/4 inch. Thats when I noticed steam/smoke coming out of radiator neck. Engine had been off about 2 1/2 hours so temp gauge had not even started moving yet. Turned truck off and here I am.