1995 Chevy Corsica cool heat...

Hello I have a 4 cylinder 1995 Chevy Corsica which blows out cool air. I checked my heater core its not leaking and I flushed it to make sure coolant can flow thru easily and no problems there. I changed the
thermostat with no luck. But today I noticed that my upper radiator hose is soft I can squeeze it together while the engine is running. I assume no pressure is building up in my system. I tested my overflow tanks cap and my system for 15psi and no leaks. SO my question is what builds up the pressure in the engine? Does the water pump bring the pressure up?
TIA for any help!
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It is pressurized by expansion of the water when it gets hot. The hose isn't necessarily going to feel hard as it is only 15 pounds and when you squeeze it you push antifreeze into the expansion tank through the pressure release valve. Is the radiator full? Is the water getting hot? do the hoses to the heater core feel hot when the engine is warmed up?

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I cant tell if the radiators full because there in no cap on it. My system gets filled thru the overflow tank. Yes the hoses do get hot to the thermostat and the thermostat does open. I've ran the car to operating temp with the cap off to burp it to release any air.
Thanks

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30W wrote:

Basic physics: Things expand when they get hot and they shrink when they get cold. A system at ambient temp should have no pressure. Throw a sealed can in the fire and it will explode from pressure build up.
Does your engine heat up at all?
A couple of things come to mind: 1) The thermostat is bad. 2) There is a lot of air in the system.
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The engine does heat up. The upper radiator hose gets hot where i can only touch it for a couple of seconds before I have to pull my hand away. The radiator also gets hot. I changed the thermostat twice already and no luck =\. I burped the system to release any air but maybe there is still more air. I dont believe my system has a bleeder to release any air. You have any suggestions for releasing the air? The way I did it was run the car to operating temp with the cap off, I also squeezed the upper raditor hose to force any air out.
Thanks
On Sat, 24 Dec 2005 02:33:16 GMT, " Paul " <" Paul

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30W wrote:

The upper hose is discharge into the radiator. If it is hot then odds are the thermostat is working correctly. The heater core bypasses the thermostat. With me not knowing the history of the car... 1) Are you sure the heater hoses are not on backwards? 2) There could be air in the system - heater core especially. There should be an air bleeder near the top of the engine.
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Did we ever determine whether the hoses to the heater core get hot. If everything else warms up maybe the valve that lets the water into the heater core doesn't work. Some of the older cars used a vacuum operated valve, maybe that valve isn't working.

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