chances are if you are triing to keep your rad full with of a catch can you prolly have a coolant jug so take a knife and make a hole and run the hose , tada i have a catch can
i filled the jug about a tird full then ran my hose into the jug so it was well into the coolant tehn just ran my hose under battery tray to rad(new by the way put it in today after the shop closed)