I am flushing the cooling system on a 95' 325i 6 cyl. The question is how do i add coolant to the radiator? Do I just keep filling up the overflow because there is no actual radiator cap? Is there a pressure release valve to make the cooling system take the coolant? I have already found the leak it is coming from the top of the radiator but I can't fix it until I can make sure that the cooling system is taking the coolant. Also since haynes doesn't make a manual, any suggestions on the easiest way to change the thermostat? Any help would be greatly appreciated. Also maybe a pdf help file. Thank you for your time!

Yes you fill through the Expansion Tank (Bimmer speak for overflow or recovery tank). After filling you may need to burp the system to get all of the air out, some of these, the E30 models have a little screw at the thermostat housing that you can open a bit, and let coolant slowly drain out until you see no bubbles in the coolant. As long as she does not over heat, the system is good to go. Thermostat should be at front of the engine at connection to upper hose, a matter of removing hose, then the thermostat housing and replacing stat and gasket (probably a rubber "O" ring, also look at the old stat as it comes out and see if there is not a arrow or notch on the stat that shows you the correct orientation for the new stat).