B16 fiat x19 2 steps forward, 1.5 steps back. Coolant issue

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so intake (bypass) goes to the closest to the thermostat, and the heater return goes closer to the pump?

I am preeeeety sure yes, that way you are creating a pressurized loop instead of only pushing coolant when the thermostat is open
nvm you have it correct
Where did you find that pic! (Rhetorical question) that is a perfect pic of the coolant system!

Have you tried getting radiator higher than the motor and bled the system? Maybe by jacking the car up or using a Lisle funnel?
Ordered! The fill for the system is in the rear near the engine. It's on the expansion tank (heater circuit). But. We are looking to add a fill point on the main circuit (possible kpro upper radiator fill) and the funnel would probably work there

Testing, testing, 1,2,3. so I figured I would give an update while I am here. 2 seniors in high school, with one of them in softball has dominated my time. Where I am at now. tomorrow I am ordering the Ktuned top filler neck. https://www.rywire.com/product-p/kt-kuw-b16-f16.htm
to put on the circuit going to the top of the radiator. I have put a bleeder valve in the return from the radiator right near the block. I figure between those and the bleeder on the radiator itself I should be able to get all the air out. if that doesnt work, then I get the vacuum method of filling a coolant system. If that doesnt work, then I get a different NEW radiator.

Progress!!!! ok so I put the k-tuned top filler neck, and bought the funnel kit. Things didnt go as planned as the upper coolant host fitting bole broke off in the head. Not enough sticking out to get it with a stud extractor. not enough threads for the double nut trick. we ended up welding a nut to the end and got it out. whew, crisis averted. Using the funnel kit, which totally rocks, anyone who doesnt have it is REALLY missing out. i filled what I could. then started the engine, as it was warming up I had a small bloop of air every now and then. then it hit 200. and one BIG burp and the temp went down!!! woo hoo!!! after letting it sit there for 15 minutes without any bubbles, ant temp never going above 200, i felt I was good. I shut it off and pulled the funnel (did I mention how much I love this thing) and ready for a test drive. Odd, it was acting like limp mode. missing like crazy around 4k. Temps were still in the high 190's. then ugh. afgter about a mile I had to stop to take a turn and up goes the temp. I stopped the engine at 210. DAMMIT!!!. after it cooled to 199, i drove it another 1/2 mile, and back up to 213. shit it down again. and waited. 199, and started it agian, this time it made it ~ 2 miles, then when I slowed down for a stop,, up shot the temp again. the stop was at the house so I pulled in before shutting it down. I got out, felt the hoses going to the radiator and they were warm, not hot, warm. Not sure what this means. but I feel i am getting closer.
so the "limp mode" only ELD shows, and that isnt a code that should cause a limp mode. what i am thinking, when I was driving, in 5th gear at 3200 rpm, the speed sensor was saying 5 MPH... yeah, not ight. looking at the sensor after I pulled back to the house, I saw it was soaked with coolant. I air blew it and plugged in back in. We were towing it back to my house, so I drove it long enough to line it up with the truck, and during that 50 feet the speed went up to 18 MPH< much better. dont know if that cause the limp mode type of miss, but I should have time tomorrow to try it.
one other thing, the ktuned upper coolant, doesnt have the nipple for the hose that goes to the intake, so for now I blocked it off, looking to find a place to tee it from.

so closer!!! thanks guys!

that was my thought as well, driving it shook the small pockets into a bigger one. going to try to burp it again today.

Ok. Update but still overheating. I replaced all the plumbing going from the engine in the rear all the way up to the radiator. I replaced the radiator with a thicker aluminum one. The old one was steel and copper. Replaced the thermostat with a superstat which people either say it is much better or at least equal to stock.
Letting the car sit and idie (which I have a fast idle issue i will discuss later) settled about 196 for about 15 minutes. The radiator was hot so I know I has flow. Revved it up a few times and let it idle again and the temp went up. Thinking I might have an issue with the cooling fans, I took it for a quick run (1/4 mile) and temp was back to 210 and climbing. After I shut it off i went up front and the radiator was warm bit no longer hot. So I am back to circulation. Cracked the bleeders and no air this time.
With this in mind I am back to a new waterpump. The front of the engine is tighter than a Honda so I don't know if I can do it in the car. If not, there goes a weekend with an r&r of the drive train.
Any other ideas on the overheating? Engine purs like a kitten with no misses and no air bubbles.in the coolant so I am not thinking head gasket. And can am blown head gasket ca use this extreme of overheating without a miss? Someone mentioned a possible bad temperature sender and it really isn't overheating. Ever heard of that in hondas?
The idle. Right now it idles about 1400 cold and 1700 hot. Could what is causing this be related?

B16 fiat x19
Is it losing coolant (aka you add coolant each time you've messed with it)? If so, a bad head gasket seems possible.
Not losing any that I can tell with only running it 5-15 minutes a shot. We are going to do a leakdown. We already pressurized the coolant system with no leaks, but 10-15 psi coolant test isn't the 150+ you get in compression.

Also if it is reaching temperatures to overheat within 15 minutes and not driving I would also say underlying head gasket issue
the good part about if it is, that can be done in car. Cracked or warped head shouldnt be an issue either as if it is, I have a second that I know is good. (the one that we should have prelubed after sitting 7 years and beat the heck out of a bearing)