The pressure is caused by the rise in temperature of the coolant, and is regulated by the cap, either on the radiator or on the coolant recovery bottle. Typically I think pressure caps are rated at between 8 and 16 PSI. You really need a well sealed system to make it function correctly. If you remove the cap and get no pressure, then when the system cools down you will also not have a vacuum to pull the coolant back into the radiator. I would certainly make an effort to re-attach that hose with epoxy. Liquid steel or JB Weld, are both excellent for the purpose. Clean the surfaces very well, then attempt to roughen the surfaces up that you are going to apply the epoxy too. I think if you work it right and carefully, you will get it done.

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Junqueyardjim
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1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
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