Yeah I was thinking it could be a wrist pin loose or a rod bearing but I haven't pulled the engine out yet to check the bearings i.e. The block is still in the vehicle and the oil pan is still in place. First order of business at this point is to get a hoist to pull the engine then I've sourced a local machine shop to do all the measuring and any honing that will be needed, I'm going to have them measure tolerances on my rocker arm assembly as well. As far as the head goes I'm just getting a new complete casting and calling it a day on that one. Looking at the numbers a used JDM 22re goes for around 1200-1400 that would leave me with a lot of spare parts for sure but a rebuild is going to cost me less so unless there is something wrong with the block that makes it unusable a rebuild is gonna be cheaper and more in line with my budget at the moment.

There is actually a relation it just has absolutely nothing to do with the temp sender sensor which I believe to be faulty on its own. The other symptoms were all due to the loss of coolant via the crack in the coolant passage between cylinder 3 and 4 which over the 500 mile drive home caused air lock due to coolant loss or more so air in the cooling system which caused no or very little heat to come from the heater box (no coolant flow to heater core no heat). It also wasn't helping the the radiator that was in it when I drove home had two Jerry rigged JB weld crack repairs that weren't holding all that well further allowing air into the system. Once I dropped in a new radiator and thermostat and filled the system with distilled water (for testing purposes) I had flow in my cooling system again and heat as well. CO_94 had the idea that the temp sender gauge was not working because of air lock not distributing the heat to the sensor which makes total sense but right now it seems more like the sensor its self or the gauge in the cluster because I got heat and radiator flow but the temp gauge still reads 1/4 at op temp.

Basically I started this thread with some rough symptoms and we all speculated as I pealed away from layers ... once I didn't see any real evidence of an intake coolant leak (which was a suggested possibility) I tore the head down and found the crack in the head gasket and corresponding crack in the head and now it seems like a rod knock or loose wrist pin in cylinder 2 piston as well ... at this point I'm pulling the entire engine and taking the block and my top end parts like rocker arm assembly and cam down to get tolerances checked out by a machinist and have the cylinders and journals measured so I know what size pistons and bearings to get. I think overall our speculation has been accurate to the point that it was indeed a one way leak into cylinder 4 but the temp sender doesn't have anything to do with the overall bigger problem. next step for the temp gauge issue is to test the sensor with an ohm meter so I'll be doing that and some other little repairs while I wait for machine work and parts.

Honestly I'm pretty happy with how this turned out (so far) I know that sounds crazy considering the multitude of issues but I really wanted to rebuild an engine and this has been extremely educational so far. In the end I'm gonna know this truck inside and out which will be an advantage when I'm off the grid and a problem occurs.

Thanks that is helpful! I already tested the temp sender sensor that sends signal to the ECU and it seems good but I realized that it wasn't the one that sends to the dash cluster and was going to have to track it down ... I only had a description that it was int he middle of the intake next to the valve cover but that pic nails it down. Thanks for the post... I'm pretty sure the temp sender is having the issue that guy describes.

Well, I got the engine pulled out last night ... took me about 6 hours to pull the block ... damn it was a pain in the rear end trying to get at those bottom bell housing bolts ... especially the two 17mm but the 14mm next to the bracket where the slave cylinder connects was also a a real pain. It will be easier next time I'm sure because a few of those bolts needed a good soaking of PB blast to get them to cooperate. I only ˟˟˟˟ up one thing in the process ... I thought I had all the fuel lines disconnected but the one leading to the fuel filter was still connected and just as I noticed the engine tilting passenger It popped and ripped it to shreds ... gonna pull one from pick n pull tomorrow after I take the block and head to the machine shop to get rejuvenated. Other lesson ... I wish I had just said forget it and pulled the entire motor from the get go ... instead I had it coming out in sections so the wiring harness is all over the place ... I didn't know I would need to go this far though and secondly I didnt know about unplugging he harness from the ECU and taking the whole thing with the engine. I'll do that on my engine stand then drop it in when it's time. Ended up using different m12x1.25 bolts that were 60mm instead of the long head bolts to pull the block.
Definitley going to pull the harness out with the engine next time this has to happen.
Here she is stripped Neked

Oh yeah and I can say with confidence the original owner/seller was a lying sack of turds. No rebuild took place ... he used a cork gasket for the oil pan at some point and several bolts weren't even finger tight so that was a major source of leakage ... same goes for the timing cover ... some bolts were barely wrench tight definitley not torqued to spec even though spec doesn't call for a lot. Also he claimed the timing chain guide was metal backed but it was plastic ... maybe he had the timing chain done but it wasn't the metal kit. Also found bits of bearing in the oil pan which pretty much confirms the knock was one of the crank or rod bearings.

Anyway she's my baby now so time to move on and build it right. My fiancé keeps nagging me to get it finished so we can go camping which I consider a good thing since most significant others would be complaining about how much money I'm spending

Thanks to everyone that helped I'll start a build thread moving forward.

Also as a note related to the original sub-topic of not having an accurate reading on the temp gauge, I verified the gauge works by grounding out the connector and checking that the gauge went all the way to hot and it did which indicates the gauge in the cluster works fine. The manual then tells you to test the sender unit so today I took a little Tupperware container and made a temp sender sensor size hole in it the lid, then I filled it will hot water at 50c and installed the sensor in the hole, then metered it to ground as shown in the FSM and I got bad ohm readings that were way over spec, it should have read 226.0 ohms give or take about 30ohms at 50 Celsius but it was reading almost 400 ohms at 50c. I picked up two other OEM sender units at pick n pull in my recent trips and ohm'ed them out and they both read within spec. So, the culprit was the sender unit its self.