Have gone through an extensive process to flush my coolant from the radiator/block/heater core. I finally got to the near end today, the step where you refill everything with water and add a coolant flush mix and let it run with the heater on high for a bit. Was going great before I turned the heater on, then a few minutes later I noticed water leaking out of one of the heater core hoses. Since i've flushed the radiator/block/heater all individually, I know each one is flowing well with no clogs. Circled it in the picture:

If this would have been successful the next step would have been simply draining and refilling with coolant, then run the car for a bit with the bleeder screw open to get the air out of the system.
Update: I've removed the bleeder screw and let the car run with the radiator cap off. After about 5 minutes, the steam coming out was extremely hot. I had put a plastic catch can near the valve to catch the squirting fluid, but it became so hot i thought it was going to catch fire. The fluid in the radiator also nearly boiled over out of the top. I'm guessing I need to do this again with the cap ON. Should I just keep running it 5 minutes at a time with the bleeder screw out? The leaking out of the heater hose has stopped since i removed the bleeder screw, but I only got to run it 5 minutes.
Or should I just forget it, drain it, and put in my 50/50 mix now? I didn't run the prestone fluid flush the 10 minutes after reaching operating temperature it says on the bottle yet but not sure how much that really matters.

If this would have been successful the next step would have been simply draining and refilling with coolant, then run the car for a bit with the bleeder screw open to get the air out of the system.
Update: I've removed the bleeder screw and let the car run with the radiator cap off. After about 5 minutes, the steam coming out was extremely hot. I had put a plastic catch can near the valve to catch the squirting fluid, but it became so hot i thought it was going to catch fire. The fluid in the radiator also nearly boiled over out of the top. I'm guessing I need to do this again with the cap ON. Should I just keep running it 5 minutes at a time with the bleeder screw out? The leaking out of the heater hose has stopped since i removed the bleeder screw, but I only got to run it 5 minutes.
Or should I just forget it, drain it, and put in my 50/50 mix now? I didn't run the prestone fluid flush the 10 minutes after reaching operating temperature it says on the bottle yet but not sure how much that really matters.