My 2012 prius over heating

I changed the engine and transaxle of my prius 2012 for rattling and knocking noise. Now the car is over heating. If i start the car and drive for about 15 minutes. The car will not on its own go off again. At stops the engine stays on and the two fans keeps blowing. The engine is suppose to go off at stops. I noticed that the down holes of my radiator pipe is always cold. The big pipe coming from the engine water to radiator. The engine water pump works fine. I have changed the thermostat. The car has 144,000 miles on it. There is no error codes. Please what could be the issue?

 

It hardly happen.
Even when I wasn't having the over heating. I don't see it

 

The same complete prius engine. 2zr

 

It's gen 3 engine. But year model is unknown. It's 2010 to 2015 prius engine swap

 

I just removed the thermostat. Still the engine stays on after 15 minutes of driving.

I'm beginning to think the issue is my ac.
This morning I was driving without the AC. The car did not give me any issue. Within 5 seconds I switched on my AC, the engine can on upon I still have enough battery charge.

When my engine was changed water poured inside the black electrical socket of the compressor.
We started the car then the AC refused oning. It was after we cleaned the water that the ac switched on.
Could it be that the ac is now damaged causing the engine to stay on?

There is no error codes.