Okay to start off bought truck back in August. bought it with 153k and currently has 192k miles. AC worked great would definitely freeze you out of the truck. It has the digital temp control unit with auto setting. So now here is whats going on.

Couple weeks ago started to get cold out and I went to use the heat so i had auto temp set on 80 and it just always seemed cold for 80. So last week i needed the defrost so i choose that option and after 20 mins at idle and temp set to 90 on defrost well i still had to get out and scrap the window clean as it was blowing cool. so I thought maybe a bad heater core but I have to moisture on passenger floor board and coolant level is good. So I checked both hoses coming out of the firewall and both are warm to the touch. My temp guage is always ran a lil under half way but my scan tools claim its running right around 190 give or take a couple. So need less to say I happened to put the heat selector to the floor last week and wow it cooked me out of the truck. So obviously I have something wrong as the ac option works in all vents just fine but I only was getting heat to the floor. Well then the cold front swooped in Friday night and we got some snow and Saturday morning I went to use the truck and it was in the high 20's and low 30's all day and I barely had heat at all coming from the floor. It was warm but well I was prolly breathing hotter than that. So now I'm stuck with lil heat and well its gonna get colder this winter.

So what I do know is most certain is I drove the truck at highway speeds for about 200 miles today and when I got home I went to check the level of coolant and wanted to make sure I had good pressure so I started to take the cap off the degasser bottle which yes I know I shouldn't do this but as the jug showed full on the cold mark and I was able to touch the radiator with bare hands I figured I should be good but was prepared for the worse. and well after being able to take the cap off I guess I can only be prepared for even worse. So go ahead and lay it on me I need ideas as I'm scratching my head.

Oh yea I even thought back in the day we use to take cardboard and put infront of radiatior to help keep in some heat so I tried that tonight and took truck for a spin and went about 20-25 miles and needless to say the heat got a lil warmer but not much and temp guage stayed the same as well.

 

I'm not sure that I follow your description but it sounds like you have two or more problems. One, your engine isn't getting very warm and second you only have heat coming from the floor vent. First check and make sure that there's a thermostat in the engine. It's there specifically to block the water flow in order make the engine get up to it's proper temperature as quickly as possible. Make sure that it's actually closing when it's cold. A missing or open thermostat will cause an engine to take forever to get to operating temp in a cold climate.

Second, you might check and see if the previous owner put a manual shutoff valve in one of the heater hoses. That could be preventing hot water from getting to your heater core.

You might also want to completely drain your cooling system and replace the coolant with the proper mix. When I first moved the far north, I didn't have enough anti-freeze in my coolant and the stuff would would freeze in the heater hoses and block them so that no how water could get to the ice. The engine and radiator where fine, but NO heat! I drove one long cold miserable trip several hours long before I got that fixed!

 

Ok so today I ended up having the truck start to rise on the temp guage after 50 miles of interstate driving so I got rid of the card board and temp went back to what it was before roughly normal. I also emptied the antifreeze out of it and filled it back up. i tried burping the system by massaging the hoses as well put truck up on ramps to get the front end raised. Also as stated before the cap on the fill jug seemed to have no back pressure and I know have went and installed a new cap thinking that may of been the problem. well after putting an additional 150 miles on the truck today and right after shutting truck off I was able to unscrew that cap with no pressure in the system again. Also the hoses are all really hot now. and not sure if there is still air in system but the upper hose isn't as tight as a regular cooling system would be with just a radiator cap. So not sure if I am going in the right direction but the water pump is what circulates the antifreeze. So making it circulate would build pressure..... So would that mean water pump is failing but just hasn't given out yet?

 

The "digital" control head is known for having issues with it leaking vacuum internally. People have opened them up and replaced some Orings

It sounds like your cooling system is functioning normally.

If the waterpump was failing it would be overheating or having a loss in cooling performance.


I'd start by verifying the heat core inlet/outlet temps. Then look at an issue with the HVAC box (air blend/distribution) Which could also be an issue with the digital head

 

Low or no pressure in your cooling system is a sign of the coolant not being very hot. The ONLY thing that putting a cap on the cooling system does is to ALLOW it have more than the standard 14.7 PSI (absolute) pressure so it raises the boiling point of the coolant so that the designers can safely allow coolant temperatures of about 230 d instead of just 212 d. A slightly hotter engine gives a better running engine, better driveability, better MPG, fewer emissions and less sludge in the oil.

I think your truck is supposed to have a 195d thermostat so your engine should read at least that temperature after it warms up. If it doesn't then somebody has replaced it with the wrong thermostat or it's bad.