Hello guys, new here with a question

[Andy M]

Hiya folks, nice to be here.
Ive just bought a 1989 supra 3.0 turbo auto in silver for ?450.
It is absolutely mint, it has full toyota S/H right up until 160k which is where it is at now, new turbo so no smoke or anything.
Unmarked blue interior with leather and every electric item working.
Bodywork is stunning, arches are what can only be described as factory fresh, and the rest of the car is consistent.
Pics to follow...

However, i was wondering what the setup was with the coolant/expansion.
Theres a radiator filler and another tank filler, i drive a cavalier which you fill via one expansion point.
On the smaller bottle there appears to be a pipe on the cap which vents to the atmosphere, and this passes steam continuously, hence slowly losing water...

What should be happening here?

Thanks again
Andy