Below are some photos showing my attempt to extract air pockets from coolant line in a F150 Lariat 2017, 5.0L, 167K miles. I am getting cold air out of my vents, both drive's side and passenger side. Cold hose to the touch flowing out of heater core since mechanic took off coolant lines to do some work under the manifold covers.
As a little background on the results of my experiment the following things I noticed:
1- I kept getting air bubbling out for some time. Just when I thought it was done burping, more air would appear in the clear hoses I used on the output of the heater core hose line. Seems as though air is being introduced into the system from somewhere.
2- when I revved the engine to 2-3K I would get a gush of coolant in my makeshift funnel on the ladder (see pics below). This I would assume is telling me I am getting flow in the outlet line of my heater core? Maybe the heater core is clogged and I am only getting flow exiting my tranicooler? I burbed air out for an hour and still no heat. The other day I sent about 30 PSI of house water via garden hose through the heater core in the opposite direction from which it flows normally (back-flushed). It flowed fine with no sign of debris floating in exiting water. I even changed out the water pump expecting to see an impeller worn to nothing, but it looked like new. I put in the new one anyway. It was an OEM unit.
3- Whenever I revved the engine I would get the gush into my funnel on the ladder, which would start filling up. The degas bottle would then run low. I would transfer coolant from funnel to degas bottle periodically. I filled the degas bottle whenever it looked a little low, hoping it was enough to not introduce air into the system.
4- I burped the lines from the heater core outlet because I had trouble finding a no-spill coolant fill funnel that fit my degas bottle. I tried making one custom but that went sideways due to a funky pressure relief cap. I bought a no-spill funnel that was supposed to fit on top of my degas bottle but the one I got from harbor freight did not have the right cap set to fit my truck, so I returned it and then made what you see in the below photos. Maybe someone can give me a link to a refill funnel that fits my truck?
5- I changed out the thermostat with a Motorcraft thermostat which I got from a local Ford dealership. That did not make a difference, still no heat.
6- I would like to add that if I rev the engine for a few minutes between 2-3K RPMs I do start feeling a little warm air coming out the vents but as soon as it comes back down to idle, outside air temperature blows out. It is kind of weird, but it seems like the vent temp gets cooler when I call for more heat. Not sure if that is just my imagination though.
7- I may be getting some humidity in the cab now but I am not sure if it was just moist morning air piling up since no heat available to chase it away. Smelling a chemical smell in the cab but I did not identify it with the coolant smell. Maybe the pink coolant smells different than the yellow? I know the yellow coolant smell for sure, and I do not think the odor was that.
8- I changed the blend door actuator with a Dorman about 6 months ago when the driver's side heat was lacking. That issue went by the wayside when the summer came in.
9- Driver's side heating issues started in Dec. 2023 when another mechanic took off manifold covers to change out a VVT solenoid. It is funny because in mid-September another mechanic changed out all 4 VVT solenoids and had to take off the heater hoses and that is when the truck was returned with no heat. When I went back he put the truck on a hill, took the degas bottle cap off and revved the engine and got a little heat. Shouldn't he have used a no-spill coolant refill funnel on the degas bottle? Is that the professional thing to do, just burp it with the lid off. Didn't they invent the refill funnel because burbing the coolant lines with the degas bottle cap off just doesn't do the trick?
10- I notice that for my truck at Rock Auto they sell a "Heater Valve" (see screen shot below) which I am hoping is somewhere under the hood, but I have my doubts. A bad one of these would be the perfect problem.

Any insights will be greatly appreciated. I am about ready to send it in to a professional.

 

That heater valve should be forward and below the battery/washer fluid fill spout in the direction of the arrow. (as per my observation on a 2016 5.0) I am guessing that it opens or closes depending on rotating switch in the cab? Check the electrical connections on it I suppose. Impressed with your setup - had a chuckle at the ladder against your house -from that height you'd really have a gravity feed. Hope things work out.

 

Thanks for your kind comments. I am starting to get coolant fog in cab. It took a while to get to that point, so it was tough to diagnose. I would guess that the hole in the heater core was responsible for the introduction to the "impossible to purge" steady flow of air into the system. I will take a look at that valve. Do you know the functionality of the heater valve? Thanks again.

 

After seeing all the coolant fog in my cab I know now I have no heat due to a leaking heater core. Must be sucking in enough air to stop flow through the core. The l leak was far from a gusher, never wetting the floor mat up under the glove box. I would think that you need a pretty sizable hole in the core to completely stop heater from working. Today I will be shunting the heater core out of the coolant loop and getting in line for service at a dealership. I am leaning towards a dealership since the entire dash has to be removed to get to the heater core from what I see on YouTube. I installed an intake manifold on my 2017 Lariat 5.0 F150 which was a real challenge for me. I am afraid of damaging sensitive wiring in steering column (YouTube video showed that entire steering column has to be taken out to get dash out far enough to access heater core) and breaking off tabs when dismembering dash so I will have to pay for that experience in doing this all the time. Any advice will be appreciated. I have to wait one week if I leave them the truck or two weeks if I want to sit around and wait while the work is done. Now that I am thinking about it might be better for me to wait the two weeks. I am a general contractor and can really need a truck every day. Renting a vehicle in Vermont (rural) can be a real hassle, not to mention expense. Maybe I will only lose 1/2 a day of work?

 

And the saga continues... Let us know how you make out.