3.0 Overheating Water Pump Headgasket Issues

[1991brg]

I have a 2001 X5 automatic with the 3.0 liter with 225k miles on it. I bought it with a 'headgasket issue' as diagnosed by a non BMW mechanic from a lady who had been driving when it overheated at the end of the summer. At the time it was around 90-95 degrees here and I'm sure the air was on full blast. Said she pulled over and shut it down as soon as the temp gauge went up and had it towed. The bleed screw had came out and shot coolant straight up on the hood pad.

She had the bleed screw replaced and a new upper radiator hose put on it and it refilled with coolant by the shop. Still has the original 2 bar expansion tank cap. Guy drove it couple of miles and it started running hot. He claimed the headgasket was blown, possible cracked head, time for a new motor at $7k.

She puts it up for sale as is and wouldn't let anyone start it until it they owned it even to just hear it run. Oil is pitch black, oil cap is black... not foamy or white at all. Expansion tank is overfilled all the way to the top with coolant.

I buy it and and start it to load it, runs fine... no issues except throwing a cylinder 2 and 3 misfire codes (cracked head between there per shop). Get it home and get the expansion tank lowered to correct level and clear the codes. Runs great... no smoke, plenty of power. Hisses when removing the radiator cap even when its cold, but no issues otherwise. Drove it approximately 850 miles without any issues at all with a couple of hour long trips and running errands in town over about three weeks time. Only thing I noted was the big cooling fan didn't kick on with the air conditioning on. No coolant loss, oil still very black and needing changed... plenty of power, no smoke or CELs.

I'm thinking she overheated it with the AC on full blast and the shop didn't bleed the cooling system correctly. They weren't interested in fixing it as they had already made their money towing it twice and with the 'repairs'. Lady's husband said to part with it and bought her a new Honda Pilot. I have left the oil alone to keep an eye on it for the time being.

Winter has hit here... over the weekend it went from 60-70 degrees to 30 degrees. Took it to the mountains Saturday, 30 degrees and rainy snow, an hour into the trip it overheats on the interstate. I stop, let it cool and get it to the next exit. With the snow everything was wet... couldn't tell what was going on with it really. But it appears to be leaking from the water pump after its shut down as its leaving puddles underneath, both where it was left the first time and the second time where I moved it to a safer spot until I could go tow it home. When loading it up I noticed a slow drip from the water pump area underneath as well. When moving it I had the heat on as high as it would go and it cut in and out too.

Any initials thoughts on it guys? It appears to have been well maintained overall, its clean and everything works. I assumed I'd be hunting another M54B30 when I bought it but now I'm puzzled. The non responsive wide safe range temp gauge and the 2 bar cap concern me. Sorry for such a long post... and thanks for the input everyone.

Put a water pump on and see what happens?