my truck 2004 Chevy 5.7 sometimes has a big white puff of smoke come out

[Tom]

on start up then normal.? on cold start white puff smoke comes out then its normal,not all the time though have had to add a gallon of antifreez (water).i can see no leaks never change the antifreez the truck has onehundredthousand miles on it.what do you think?

 

[ScottW]

If ur truck is 2004 it will be either 5.3 or 4.8 they did not use the 5.7 in 2004 anyway the white smoke is oil that leaked in from the valve seals leaking over night,but keep a eye on that antifreeze to make sure its not a head gasket thats bad.