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Old 01-03-2015, 03:38 AM   #10
piecesparts
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Join Date: Nov 2003
Location: Lebo, Kansas (middle of nowhere
Posts: 6,821
Re: No pressure in upper radiator hose. Is this normal?

Think of it this way, IF you boil or heat water in a confined space, it will expand and create pressure. That is a law of physics. So the older systems did not have a collection/return system on them, they just pressed up to a point that they would hold pressure and not boil or they lifted the relief on the radiator cap.. The later systems had a radiator cap that relieved to a bottle and then had a small orifice that would allow water to return to the radiator when the system cooled and the coolant inside shrank back down. The upper hose should get firm or somewhat solid as the system presses up. If it is not pressing up, then something is letting pressure out and your water is going to boil at a lower temperature. If you want to, you can change the cap to a later style and add a return catch bottle to you truck.
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