heater core

hello, I just replaced my heater core and the new one is the same a sthe old one, leaking from the overflo valve. and now over heating bad. Then also I started my engine and attempting to manuver a way to keep the brke lights off, I was moving around the main wires near the stearing column and it stalled my car, so I removed some of the electrical tape and found 2 wires coming from the column and then 3 wires coming from the other direction and they appear to be spliced and soldered. Do you know if thats normal? Thanks for and ideas and comments.

Sounds like you need to flush your cooling system.