Volvo 1994 Radiator

try looking in the manual or on volvo's website(they should have online manuals. and i think you are looking for the coolant fill bottle. it should say "caution, high pressure, do not open when hot" or something similar. if i am not mistaken it will also be full of ither green or pink(original) liquid. if you cannot tell, then opn the caps of different bottles(over 2litres) under the hood, the one that smells 'sweet' or similar to the coolant that you are putting in, is the 'rad' cap. (they don't put the rad caps on the actual rads anymore)

hi my name is paul
these days most cars have a expansion tank under the bonnet or hood
this is were you fill it up with water it looks like a plastic bowl with a screw lid
DO NOT UNDER ANY CIRCUMSTANCES UNDO CAP WHEN ENGINE IS RUNNING OR IS STILL HOT *** DANGER OF SCALDING DO NOT OVERFILL CHECK OUT MAX LEVEL
car manufacturers use expansion tanks because as the water in your engine warms up it expands under high pressure and fills up the expansion tank with excess water when the engine cools down the water cools and it shrinks and goes back into the cooling system hope this information has been usefull
regard paul