Top Radiator Hose Collapses

Have you read any of the responses? Stop guessing and think. The pressure in a closed system is directly proportional to the temperature. When the temperature in your cooling system drops the radiator hose is collapsing. What does that tell you? It tells you the pressure is dropping and it is a closed system.

It needs to be vented to atmosphere somewhere, whether at the radiator cap with no bottle or at the bottle.

Read the above as many times as it takes to understand it.