A bit of background story - in December 2021 I was driving my DeLorean to work and suffered a split hose between the water pump and passenger side head. During this incident the temp gauge briefly hit the 240F mark before I was able to safely get the car out of traffic and into a parking lot. Once I got the car home, I let it sit for a day and then drained the oil to make sure there was no coolant in it. There was absolutely no sign of antifreeze in the oil, and my plastic oil filler screen was fine so I figured I dodged a bullet regarding overheating. I decided it was time to replace all the coolant hoses in the engine compartment for the second time of my ownership (last time was probably 15 years ago). This of course spiraled into other projects while I was in the valley and etc etc and today my car is finally 100% working once again.
The coolant system was actually done a couple months ago but I haven't driven the car much at all since then because I was getting my angle drive rebuilt. So, I had already bled everything a couple times and thought all was well. Angle drive is back in tonight and I went for a long-awaited test drive.
Unfortunately I am finding that my temp gauge, after about 20 to 30 minutes of mixed residential and highway driving, is reading about 215F which is a fair amount higher than it ever used to be for the previous 20 years of my ownership. I used to always sit just above the quarter (160F) mark. My fans are both on but they aren't really doing much to drop the temperature. They are coming on probably around 175F just like before. It's getting just below 220F and even sitting idle, hot, fans and A/C on, it's not on 220F but not falling much either.
A couple other observations and comments -
1) No white smoke or anything like that from the exhaust
2) No odor of coolant while running
3) I checked the overflow tank a couple days ago and the level was about half, maybe slightly below half, full.
4) New 15 PSI radiator cap from DMCMW
5) I have a continuously bleeding radiator housing (DPNW) that returns to the overflow and have had that forever
6) New DPI radiator bleeder kit - I bled the radiator again while it was just below 220F and some air and steam came out so I think it's finally REALLY bled, but I went for another drive after that and no improvement
7) Coolant replaced with fresh 50/50 green during my valley overhaul
Before putting the intake on I rented a cooling system pressure tester from Autozone and I was holding pressure after finding a few small hose clamp leaks.
9) New thermostat and gasket installed from DMCMW
10) Ever since my valley rebuild was done, I seem to be burping a couple ounces of coolant out of the overflow tank hose about the time I pull into my garage after a drive. At first I thought my overflow tank was too full (I filled it to about 3/4 full initially) and I was hoping this burping would stop once it found the right level but now I'm worried it's a sign of something else.
What should be my next steps to diagnose this problem? Here's a picture I took before pulling the car into the garage for the night. Incidentally, my volt gauge does read lower than actual alternator output (actually measuring 13.4V with a multimeter in the engine bay) but it's been doing that since before the cooling system issue.
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