Update : Just drove the truck from a cold start for less than 2 miles and she loss heat to the cabin, the temp gauge fell to cold and immediately to overheating, oil light came on(gauge showed good pressure), threw the code for engine fail safe mode and spewed coolant from somewhere near the reservoir tank. I turned it off for less than 10 seconds, turned it back on and it was at regular temp again, with heat to the cabin. I opened the reservoir tank and there was a bunch of pressure. I drove it back home, and the whole way back it sounded like there was water rushing behind the head unit. Finally got home and checked the tank and hoses. The upper radiator hose that leads out of the thermostat housing was tight and hot. When I opened the tank,there was pressure...but not a ridiculous amount. There was an immediate drop in the firmness of the hose once I opened the tank to release the pressure. Has anyone ever found a solution to this yet? If so, care to share? If not, any thoughts? Thanks in advance!

Also, was there two versions of the CHT? I see one wire that has two connectors (1 prong and 2 prong) and lead to the same location. The only ones I've been able to find have had two prongs, and I would like to change it out. This is what I believe it to be. It's low on the front of the driver's side of the engine.

Red circle is sensor in question.
Red arrow is lower rad hose.

 

When the engine is already warmed up, disconnect the cht in question when engine is off, then start it again, check temp, if gage did not move than you found your sensor,

 

Alright, so I found online where the actual sensor is. It's behind the alternator under the intake manifold.

 

Alright, so I went and grabbed one of those exhaust gas testers, and tested for gases present in the coolant reservoir tank while the truck was idling and cold, warm, and after a trip to the store. The fluid never changed color, so I guess it's not a head gasket leak. Now I have no idea what the issue might be. The upper rad hose was hot and tight when I got home again. I went to Walmart real quick and there were no issues whatsoever. From there, I went to Target. The truck was still warm, so I went on my way. At the end of the trip, it sounded like there was water rushing behind the head unit. On the trip back home, there were no issues still, but it still sounded like there was water rushing behind the head unit again. I was in both stores for like 20 - 30 mins, so not too much cooling was able to happen. Any thoughts? Thanks in advance!

 

It sounds to me that you have some blockage in the system. Have you confirmed that the heater core is flowing ? You might try flushing the whole system

 

The radiator, hoses had heater core were all replaced. With the heater core came a fluid flush, so I believe it was taken care of.

 

So just to make sure dud u change all the hoses, upper is a given from your previous post, but I'm also referring to the lower, both heater core, and resivor over flow hose (small one on top left side of resivor connecting back to radiator) if so then has the engine block been completely flushed, perfect example using a water hose spraying water into the thermostat loc a tion (without the thermostat obviously) and seeing how much pressure is coming out the block where the lower hose would connect.

 

i had this exact issue in my 97 years ago when i had the coolant changed by one of those 10 minute oil change places. It totally screwed up my truck for a long time. It would operate fine, heat up fine and then out of nowhere i'de loose heat, temp guage would fluctuate then ping at overheating spitting coolant out the cap. Then i'de hear a "burp" type noise and then coolant flowing fast, temp guage would drop to normal and heat would come back.

My mechanic was stumped, he purged teh system several times and it would just come back. He was set on thinking the headgaskets were shot and spewing exhaust into the coolant. I didn't want to go that way.

This is what I did, i took the thermostat and drilled 2 small holes in it. This way if the tstat doesn't open the coolant would still flow through or let any airbubble through. I also added redline water wetter. This to me helped, as I started to think i was suffering from electrolysis of the coolant. Once I did these 2 things, the truck never once ever again overheated or had the issues I was experiencing.

 

oh and your going to have some pressure in the coolant system and when you release the cap you also release the pressure so the heater hose will go limp.

 

I sold parts for a big auto parts store for many many yrs...and the one thing I can tell you fir sure is that there are indeed brand new replacement parts that are bad right out of the box,bag,ext....I'd bet money your thermostat is bad...I had it happen to me before ...I'd have a problem install brand new parts and still have a problem and fight with it fir a long time because the new part was bad..we don't expect our brand new parts to be bad,but it happens...I'd bet anything that if you replace the thermostat again all your problems will disappear and your prayers will be answered....I can't imagine how frustrated you are...and if you don't figure it out soon that old truck isn't gonna handle getting hot too many mire times before something major like warping or cracking a head is gonna happen...hell take the thermostat o it all together and drive it around....I would bet the house you'd have no problems with it ever getting hot....good luck my friend....I feel for you