Sorry for the easy question guys, but I am used to having a pressure relief screw on the thermostat housing.
I got the 5.4 in my 02 Expedition, and just had to replace the overflow tank.

I def feel like I have some air locked in the system, as it still overheats when we head down the road and limps into the Cooling Safe Mode.

I am 40 miles from town, so its hard for me to get into town to buy a Haynes, or other manual for a explanation.

Thanks!

 

To get any air out of the cooling system, just keep the coolant level in the degass bottle up to the specified mark.

The first few times you drive the vehicle any air in the system should end up in the degass bottle. When the coolant 'cools', coolant will be sucked back into the engine and the level in the degass bottle will drop. Just keep the level up to the spec and any air willl stay in the top of the degass bottle.

 

Thanks for the tip. So here is my situation as of now.
I leave the overflow tank cap cracked in attempts of letting any air escape. Every 15 seconds or so the fluid start to rise, sometimes to the point of some fluid escaping but you can also hear air squeeking out. I let this happen for well over 30minutes. When I drive the truck it goes up to about 3/4 Hot.
One thing I noticed is the inlet hose to the heater core is nice and hot, the exit hose is nearly cold.
I'm stumped...at this point. I have replaced the leaking overflow tank, and the thermostat.

 

I'd check for a bad head gasket. Put a pressure tester on the cooling system and see if it holds pressure. Can you see it raise the level in the bottle if the pressure leaks down?

Or have a shop hook up their 5-gas analyizer to the coolant and see if it can detect exhaust in the coolant.

 

Check the temp of the inlet/outlet to the rad. If the return is not hot then sounds like blockage. Can the t'stat be put in backwards? A po'boy check for pressure in the system is to squeeze the rad hose, check for different resistance when hot vs cold.

 

I noticed last night that the top radiator hose was super hot, and the lower hose is just barely Luke warm. Matter of fact the coolant being pushed into the overflow tank I could stick my hand in, pretty cool. The truck said its overheating and the coolant in the overflow was barely hot...thought that was odd....but might be normal.

 

I'd expect the lower hose to be more than barely hot. I'd suspect there's not enough circulation due to blockage or t'stat not opening. Some engines will let you put it in bass-ackwards. You mentioned it was replaced, did it get put in the right way?
PDQ's comments also sound likely. A blown head gasket could be a real PITA. Hope it's something simple.

 

Is the return line hooked up? There should be two lines attached to the tank, coolant and vapor come in from one side, and only the coolant leaves the other side. If the incoming line is disconnected or blocked, the vapor in the engine will push the coolant out and into the coolant tank.
The engine will physically run, and can circulate coolant, but it cant get the vapor out of the block and so the vapor fills the heads and gradually pushes downwards. This will cause all sorts of garbage to burn onto the sparkplugs and will ruin your oil in no time at all.
The truck will also usually tick until you replace the plugs.