A couple years ago we had some threads re. cooling and after studying a the Service Manual coolant routing diagram I declared that the common wisdom of removing the tstat to improve (or fix) cooling wouldn’t work for us. I said that when the tstat opened up and allowed coolant from the radiator to enter, it also closed off the route from head to pump.
This is important because it means that in the absence of a tstat coolant is free to go from head to pump and bypass radiator. And given that the front of the pump is the lowest pressure in the system, that will be the preferential route.
Yesterday I got to fooling around with one of my take-off tstats. I pulled it open and found that the tstat had been gutted. I reacted to that with “holy shit, if this worked for whatever car this came off of, that means my “don’t remove the tstat” idea was wrong”.
So I went out to the race car so I could see the hoses and spent some time visualizing what the coolant route would be with the tstat both closed and open. I kept coming back to the same conclusion. If that tstat is not in place, functional and fully open, hot water is going to go from the head right to the pump and bypass the radiator. There’s just no way around it. So the PO of this tstat housing punked himself and probably did a lot of wondering as to why his car was always overheating.