engine drinks loadsa water,?

my zafira is drinkin too much water,has gunky stuf on oilcap, hav smoke from tailpipe, and water splutering out like drips, iv done oil change, witch oil was brownish, offcolour, iv used kseal in waterbottle to try bloke a hole? still smokey, havnt lost any compression, still pulls, ?? its ovaheating,??? thanx