Still indicates being low on coolant.....

 

Thanks buddy, I've bought some more coolant and will take it on a good long run and give the gas pedal a workout at the same time

 

Carrying on with this issue of mine, everything seems fine, heats up nicely from cold, good gas pedal response and the gauge sits on the halfway mark. 2 hour drive, no overheating. Heater works well when it is just idling, however once on the move the heater turns to blowing cold air when the dial is on heat, it blows warm when you gun it but once back driving normally it'll be cold again. Really weird. I have put nearly the full capacity of coolant in as in the quantity stated in the manual. When I replaced the thermostat and radiator, I fitted a 93 degree thermostat, ordinally it was fitted with a 88 degree one. Would this cause this issue with the heating?

 

Thermostat temp won't do what you are seeing.

How are you vents controlled? Are the vacuum, or electric? It seems like the blend door (the one the controls how much air passes thru the heater core) is not staying where you tell it to be.

 

We did start to strip some of the dashboard to get to the door, however it looks like the entire dash needs to be removed. I did notice that everything opens and closes with the door flap when part of the dash was removed.
I'm guessing it is vacuum operated, I can hear the different stages operating when you change the direction control for defrost and facia and floor.
As you suggest, the door isn't staying open?
I really appreciate your help. You have been a great help indeed. Thank you.

 

Since your coolant, and temp are stable, I would think the problem is in the heater box itself...... It's just a guess, but, I've been doin' this kind of thing for a while.

I don't know enough about the newer trucks though, I own/worked on the older fellers.

How ARE the doors controlled? Are they vacuum, or electric actuators?

 

Just guessing but have you looked at the recirculating door above the blower motor? A known problem.

 

if the door is not staying open it could have broke. They typically break near the part that attaches to the actuators.

 

When we had part of the lower dash out there was a movement from what appeared to be the hot and cold flap.
Maybe we need to get the rest of the dash out to inspect further up, would this be correct?
Thanks Guys

 

You can view the recirc door by removing the glove box.