Pressure build up in cooling system on 1990 Dodge Ram Wagon B150

From a cold start the truck begins to build temperature almost immediately. I have changed the thermostat and in the process i hooked it up without the thermostat to make sure the water pump was working (it was). The return line that comes from thermostat back to top of radiator is building a lot of pressure and does not seem to be getting hot at all. why is the truck getting hot? also, if i take the radiator cap off while the truck is running it will actually start pushing fluid out.. light it doesnt have anywhere to go

by in Warrens, WI on December 12, 2012
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1 answer 3 comments
ANSWER by , December 12, 2012
You cooling system is vapor locked, is there a small 5/16 hex head screw or bolt at thermostat housing, most newer cas have this to bleed the air out of block and hoses.Its building pressure do to not enough water in block. System seams to be full but is not. Hope this helps!
COMMENT by , December 12, 2012
i do not see a bleeder anywhere. could I take the cooling temp sensor out and bleed it through there?
COMMENT by , December 13, 2012
From a COLD (sitting overnight) START , with system full and cap on , start engine and put hand on top hose(safely) if you feel 'bubbles' or hose is getting firm within 1-2 minutes , then have qualified shop do tests for leaking headgasket.
COMMENT by , December 14, 2012
It will spit water all over if ya try and start it. Mabee while you fill it ok. Sometimes starting the motor with it cold and water ful at radiator for short spurts several times sometimes breakes it loose. checking manafactures coolant quantity and adding that amount to make shure full is a good idea. If water pump is working most likly, and coolant full, you might have other issues.