99 Chevy Malibu fluid loss?

[lostin90s]

I have a 1999 malibu with 3.1 it will go for months with no problems and then puke out ant freeze. Can be 80 out or 30 below ant temp. Happened several times over years. The oil clean .no white in it . Not a clue .

New hoses ,water pump , pressure tested OK clean plugs . had intake redone . Still same.

Any ideas?