Well the hot water valve is definitely not closing completely. Either the cable is out of adjustment or the valve itself in the heater hose is leaking past the seal internally.

 

Mine does the same thing. Gets hotter than the blazes in the cab on hot days. I put a new valve on, but, it still won't completely stop the water flow apparently. I am going to check and see if maybe it isn't closing all the way. Other than that, not sure how to cool it down.

 

My use to do all the above also.
1.I replaced the water flow valve an adjusted the cables an it still had warm air coming into the heater box vent.
2. Aw all the flapper valves side foam had dry rotted to stop the air flowing around the sides.
3. I have pissed away money on the rebuilt heater box kits the don't really stop the air flow around the sides.
4. I ended up gluing the kits together to stop the side flow of air.
5. Back in the 70's I used some felt pad my wife had an it works good for yrs.
Then one day noticed, I had warm air flowing in and all the slider levers were closed that's when, I dug into it.
After replacing the heater valve ab adjusting the cable in the engine bay was when I found that the heater box rear flapper lever switch cable was not holding the cable
an broken. I hit pick n pull got another heater box from a 70 pickup. This was when, ordered a heater box kit an found none were worth a dam.
I should have left the foam alone that was in the replacement box. That when I order the H box kits as each one from DC, NPD,MAC, Were all to narrow to for the flapper lever seals. I have found some packing foam ideal but all to late as, I put my heater box back together.
Once you get your heater box apart you'll see what, I am talking about the side flappers need the sides sealed also you'll have to make your own.
Good luck.
Orich
.

 

Same thing in mine. But not hotter. I put a new valve in last year or the year before and it shuts off the heater core pretty well.

The foam is definitely shot though. Maybe I'll take it apart and seal it up again before this winter hits.

 

You could always disconnect the hoses where they go into the fire wall (on the engine compartment side) and connect the two hoses together for the summer. That way the coolant just makes a loop and doesn't go into the heater box.

 

 

 

I have a 3 hour trip in 90 degree weather tomorrow towing the boat. I am taking two measures for a comfortable, and hopefully trouble-free trip:

1. Taking the Interstate all the way to keep my airspeed up (as in the speed of air flowing through my radiator, and transcooler), and to minimize starts and stops.
2. Just got the blue painters tape out and taped closed the heater box outlets. I couldn't find my duct tape. But, the blue should work fine short term. I like the idea of hooking the lines together for the summer time.

 

 

I dunno. The ones I post are ones Numberdummy has posted in the past and I saved them. I think maybe you can save a pic to a pictures file. Then post from there.

 

It's probably the vent door inside the heater box that is not closing or is leaking.

 

Actually you will still have the same problem. The unwanted heat from the core will overwhelm the A/C and performance will be poor.
I also have the same issue, and had to bypass the heater core to get the A/C to actually cool anything. But who needs a heater anyhow?

 

Has any one checked out http://www.detroitmuscletechnologies.com/ DMT for a heater gasket kit?
I have not for any Ford stuff but have used them for my 70 AMC Javelin heater box restore.
If they don't have a kit for your truck you can talk to them and see what it takes to make one.
May need to send them a HVAC box so they can see what is in order to re-seal one.
I know that's what they did of the AMC guys and once it is made they then have the pattern for others.
Dave ----

 

had the same issue with my step dads truck . found the heater hoses were going to the wrong side. Switched the hoses and no more heat when off.