160, 170, 180, 195 T-stat's all in good shape, should open, be wide open at or about their designated temp. Could a new one be bad, of course it could. Any question, put in a pot on the stove with a candy thermometer clipped to side of pot. You can see it open (when it gets to specked temp) and see it close as it cools.

What temp do you want to run your engine at? In our 68 F-350 I chose 170 because of Vapor Lock problems and have a puke tank to keep the radiator full to brim at all times hot or cold. It's eliminates aeration in the system that's there when you leave an air gap in the top tank. Eliminating Aeration bubbles in coolant can help in heat transfer away from the metal of the block.

If I have a cooling system open for repair of some kind, I always bleed the air out of it as I fill the system so as to not have an air pocket(s) trapped in there, usually the heater core or a pocket in the block. If the pocket in the block stops the coolant from reaching the T-stat, how is it going to open? Some T-stats have a small weep hole drilled in them and will allow air to pass and let coolant up, tho slowly. Others have no weep hole and can cause a complete blockage not allowing coolant up upon initial fill up.

On fill up and bleeding, fill the system with the T-stat remove OR the heater hose that is highest at the engine disconnected, OR the temp sending unit removed. The block will fill completely to that level. Now the Heater Core, The hot water out of the block to the core is the hose at top of intake manifold near the T-stat, leave that hooked up. If the heater core outlets are one OVER the other, disconnect the top most hose and place the hose to rest higher than the outlet it goes on. Continue filling the system until coolant pours from the disconnected heater outlet. The coolant in the hose will be at the same level as the heater core, slip your hose on and tighten. Now the level in the radiator is at the same level as what is in the block and heater core. Just fill the radiator up to the top and done.

Puke Tank or no Puke Tank, With the Correct Pressure Cap (# wise) on the radiator, I'd use the one recommended for the truck, be it 4, 7, 9, 12, 15# or whatever. When the engine warms up and the coolant expands, it will push the expanded coolant out thru the cap either onto the ground (no Puke Tank) or to the Puke Tank if you using one. If you have a Puke Tank, you MUST have a Recovery Type Cap, to allow the coolant to return to the radiator as it cools.

Any comments about what said here are welcome, especially if you think something I stated is wrong, Thanks.

Cap

 

Thanks for the info , I will go back and make sure all areas are full of coolant. In 302s I have owned previously I always ran a 160 T stat, for whatever reason this one seems to get too hot slower with a 180.
I’m not sure what psi cab is on it , it came with the aluminum radiator, but I’ll check to see what’s called for and change if needed.
I’ll let you know if anything changes
Thanks again, I Hope something easy shows up, I had to do a lot of backing up instead of moving forward. I past ready to go for a cruise and enjoy what I’ve done, instead of getting frustrated cause of problems.

 

Go easy on being frustrated, tho understood. So you'll have to turn over a few more stones to find it. Pressure cap should have a # on it, maybe near one of the ears where your fingers grab putting on or off. Without reading back, are you using a puke tank? The variation of water pumps and housings bothers me. Hope it's simpler than digging there.

Cap

 

I don’t have a tank yet, planning to get one, so I will get a closed system cap. And look up correct pressure before