Hello to all and forgiveness please for my not having the patience to search through hundreds of pages of tips and info here.
I did try though without much help, at least nothing that I didn't already know.
The search box wasn't much help either.

I have a 94 F-150
5.0 EFI
4x4
Auto
Approx. 150,000 miles

Ok then, much to my dismay my truck is overheating.
I have a plow blade on it and went out to plow my drive and road the other night.
The second time I've plowed.

Everything was working as should, heater... defroster... and so on.
My cooling system has never leaked since I've owned the truck.

At some point about 45 minutes into plowing I noticed my windows fogging up so I opened up my passenger window.
I did not think to look at the temp gauge, nor did I notice that the heat wasn't working because I plow with my driver's window open.

A short time later I noticed the steam coming from under the hood.

I parked the truck at that point.
I was too busy to mess with it for a couple of days, as well as I had a client's vehicle in my shop at the time (98 Dodge Ram 1500) with the rear-end taken apart.
I didn't have any room in the shop for my truck and I wasn't working on a fluid issue outside in the freezing cold here in northern Minnesota in late Dec.

The following day, without really diagnosing the issue (my stupidity, I'm just too tired and busy these days), I bought a new thermostat from my local auto parts store and installed it promptly so I could get back to plowing my place (no, it wasn't Motorcraft and I DID do it outside the front of my shop door).

The truck still overheated.

Ok, what have I done now ?
In the past week now, I've replaced that thermostat, then replaced the water pump (forgot to burp it though), and now I've bought that no-spill funnel to "professionally - right" burp it.
I've purchased a new radiator cap (13 psi) but haven't used it yet as the system isn't burped / functioning properly.
I've removed one heater hose end at the engine (coming out of the pump) and was able to blow through it, pushing coolant out of the pumps outlet tube on the top of the engine. Note, no coolant fell from this hose when I removed it from the tube. It seemed dry !

Years ago (I'm nearing 60 now) I remember burping the system by just leaving the radiator cap off and watching the coolant cycle while the thermostat opened and closed until the bubbles stopped appearing.
My system isn't operating like that though.

While trying to burp it with the funnel, I noted these things:
The "burp" kit is cheap to say the least, but with the aid of a couple of larger o'rings I was able to get the funnel to seal... sort of... it still leaks if I push slightly on the funnel ( I may have fixed this though).
A lot of air bubbles DID come out, then they stopped appearing.
When the bubbles quit, the coolant began to push up and out of the funnel in a surging motion, it would suck in and then push out... and usually pushed more out than it took in.
I was struggling with my turkey baster to remove the fluid as fast as I could to prevent it from spilling over onto my shop floor (I have a shop kitty).
When I began the process there was only about an inch and a half of fluid in the funnel, even less than the instructions called for. It filled up and over pretty fast though, maybe 3-4 minutes.
The heater hoses (neither) did NOT get hot, not even warm ! However, the tube coming from the water pump that supplies the heater hose (input I think) got HOT ! Hot Hot !
Two inches to the left though, on the other side of the "T" the hose was COOL.

So to summarize;
I lost heat @ the heater.
Engine overheated briefly.
Replaced Thermostat.
No leaks observed.
Engine overheated still.
Replaced Water Pump.
No leaks observed.
Engine overheated still.
Tested Heater Core - it was clear enough to easily blow directly through the entire system.
Attempted to burp the system.

Do I have a blown Head Gasket ?
I don't have a pressure tester, yet.

What else could I be missing ?
Why did the heater hose seem "dry" on the inside when I took it off ?
Why did that same heater hose remain COOL while the tube that it is connected to that comes directly from the water pump get HOT !
There is a "T" at that connection point that leads upwards and apparently preheats the air intake before returning to the block ?, but I have no clue what that could have to do with interrupting the flow between the tube and the hose ?

I hope I've included enough necessary details to help without going overboard.
I'm headed out to the shop to take the thermostat out and make sure that it does indeed work (boil it) and at what temperature it opens (infrared thermometer) and that the unit is placed facing the proper direction, something that I DID note while putting it in, but hey... anybody can make a mistake, even me.

 

I see a lot of overheating threads on this forum, and the two things I notice in yours are that you did not use a Motorcraft thermostat, and that the best way to check for the type of HG leak you're looking for is the combustion gas in the coolant chemical test.

Maybe it just got low on coolant and overheated and you could have just refilled it, and the non-Motorcraft T-stat actually created the new problem. Or maybe it overheated and and blew a headgasket and it's overheating now because of the blown HG. Or maybe the HG blew and that's why it overheated and still overheats.

The main point is that you changed the T-stat without knowing if was really bad and now you might have the "non-Motorcraft T-stat" overheating that many people seem to have. It seems very common, don't understand why, but seems to be a real thing. But, for problem-solving, you created a new possibility instead of eliminating one when you installed the aftermarket T-stat.

If I were you and had the time I might just put the original T-stat back in, refill, and see what happens. If it still overheats get one of those chemical combustion gas testers and test for a bad HG. A pressure tester will test the coolant passages but won't test the cylinder sealing rings that contain combustion gases. You want to know if the high pressure of the cylinders is pushing gases in to the cooling system.

Merry Christmas and good luck.

 

BarebonesXL,
"Maybe it just got low on coolant and overheated and you could have just refilled it"
"If I were you and had the time I might just put the original T-stat back in, refill, and see what happens"

Actually, the first thing I did was to start the truck the next day, thinking that maybe it just overheated due to plowing.
It did over heat again. . . with the original thermostat in it.
Thank you for your reply though.

 

That, and ALL the truck's OTHER details & history, should be in your signature as this page explains:

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Have you MAINTAINED the cooling system since you've owned the truck? The coolant must be changed after 3 years of contact with metal (or sooner) regardless of miles driven (even if it's zero).That indicates a leak, or venting of coolant due to overPRESSURE; it does NOT indicate or even suggest overHEATING. After an engine is overheated once, it will not run properly again without a rebuild (at least) or replacement.No, it didn't. It might not have even gotten hotter than normal. The release of steam cools the system even moreso than the same coolant passing through the radiator would.With what (brand/PN/source)? Why - what test did either one fail? Did each replacement pass the same test?If the system is working normally, it will automatically release the air through the cap & refill itself from the overflow tank.The system will work better with a working cap.So you unhooked 2 hoses? Because you only mentioned 1. Pics would have helped.Then there's no flow through the heater core, which should ALWAYS have flow when the engine is turning. You should unhook both its hoses FROM THE ENGINE and use a garden hose to backflush it until it flows clear & easy in both directions.

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That means there WAS flow through the other branch of the T, so the WP was probably working.No reason to think so, but a quick check of the spark plugs would answer that. If one is sparkling-clean like new (distinct from the others), it's being steamed by coolant coming into the combustion chamber.That's not much use except for finding leaks. To use it for a head gasket leak, you'd have to remove all the plugs, pressurize the FILLED coolant system for a while, and then spin the engine. If coolant shoots out of a plug hole, that cylinder has a HG leak.Maintenance, usually.Because there was an air pocket there, probably due to the restricted heater core.Partly because there wasn't enough flow through the heater; partly because the thicker hoses take longer to transfer heat than the small one or the T.Flow is the other way; it comes from the pump, goes into each side of the block, mostly to the rear, up through the HGs, forward through the heads, back together at the front of the intake, and then out to the heater, throttle body, thermostat/radiator, and bypass (back down to the pump).The spring & wax chamber go to the engine side; the pointed end goes toward the upper radiator hose.