2002 Mitsubishi Montero help

Had a problem yesteday with my car. Noticed the Engine overheating and leaking some fluid. Took it to my shop and he showed me that the radiator had a crack in it. He fixed that with a brand new radiator. Drove it home and it appeared to be fine howver the internal heat gauges seem to be going up and down. When it was getting warmer the ac would be less cool. Thought nothing of it till the next day.

started it up and got in. The check oil light came on and the heating gauges are going way up. I turned around and took it home. Checked the oil and it looks full. Engine is making a small knock sound. When I first stopped it at the gas station I saw something leaking from the bottom. I think it was the same fluid from yesterday's radiator.

help