Top Radiator Hose Collapses
Every coolant recovery can I have seen has a vent. We sell 2 sizes at work. They are vented. I am in the process of adding one to my truck now. I decided against either we sell at work, because they're stupid lookin. I am going with the 87 model Ford truck one, because it is the coolant recovery tank and washer tank in one unit. Since my washer motor was toast, I thought I would do something to fix the whole thing.
But the tanks have to be vented or you will experience what you have.
Bottom line is this. SOMETHING is holding the vacuum. 'TAINT too many things it can be and they have ALL been listed.