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Hey guys, I am new to the 7.3 world and need a little help with my 96 f250 7.3. I bough the truck with 164,000 original miles on it, all stock. A couple of days later I was driving through town and the heater core cracked, sprayed a coolant mist all over the inside of the cab. I immediately shut the truck off and got it towed home. I replaced the heater core, as well as thermostat, and did a full coolant flush. After install, I fired it up and had no heat inside the cab, and the truck temp (using the stock dash gauge) slowly and steadily climbed up to between the "R" and "M" on the normal before I shut it off. The upper radiator hose was also gaining a good amount of pressure when the cap was screwed on all the way, and was hard to squeeze after a couple minutes of the truck running. I let the truck cool and tried this a few more times with the same result. So I thought maybe it could be a plugged radiator. So I pulled the radiator and flushed it until I was confident there was nothing left in there (clean water flowing out as fast as it was flowing in) and reinstalled it. I also flushed the new heater core I had put in just to make sure it was not blocked. I then put in new coolant and started the truck, with the same results as before. Finally, after searching some more, I decided to replace the water pump and put in another new thermostat to ensure that was not the issue. I also replaced the degas cap to eliminate that issue as well. I replaced all of those components and still have the same issue. The truck will slowly but steadily run hot (between the R and M on normal) over a span of about 30-35min when idling. If I leave the cap off the degas bottle, the coolant level will rise some, occasionally overflowing a little but and let out some large bubbles. If the degas cap is on and I let it run for a while, the pressure seems to build in the upper radiator hose to the point where it is very difficult to squeeze. I also still have no heat in the cab at all. Any ideas on what's going on or what I can try next? Is there a possibility it's just air still stuck in the system, or is it the dreaded head gasket failure? I have no signs of smoke or milky oil, and I cannot smell any oil or diesel in the coolant, as well as no smell of coolant in the exhaust. Any help would be greatly appreciated!
 

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The system will have some pressure when up to temperature.
The stock gauge on most trucks at operating temp will show the needle near the middle / at the R or M.
There is a temp valve for heat on the heater hose just before it goes into the heater core under the hood. It runs on vacuum. It could be stuck closed and that is why your not getting any heat (hot antifreeze) to the heater core.
 

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The upper radiator hose was also gaining a good amount of pressure when the cap was screwed on all the way, and was hard to squeeze after a couple minutes of the truck running.
That's normal.
If I leave the cap off the degas bottle, the coolant level will rise some, occasionally overflowing a little but and let out some large bubbles.
Also normal.
There is a temp valve for heat on the heater hose just before it goes into the heater core under the hood. It runs on vacuum.
Got a pic of that? Mine doesn't have it, and the A/C control has no way to operate one.

(phone app link)


(phone app link)


(phone app link)
 

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There is a temp valve for heat on the heater hose just before it goes into the heater core under the hood. It runs on vacuum. It could be stuck closed and that is why your not getting any heat (hot antifreeze) to the heater core.
That may be a modification that some have done to keep hot coolant from circulating through the heater core when the AC is on. It is a fairly popular mod in the hotter climates.
 

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That may be a modification that some have done to keep hot coolant from circulating through the heater core when the AC is on. It is a fairly popular mod in the hotter climates.
Yeah there was probably an article on it in the old FAQ section that is MIA. Older Ranger valve I think? Cheers!
 
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