BMW: 92 325i overheating problem, radiator fluid, coolant level

Question
Hi,
 I have a 1992 325i (E36) and need an experts opinion.
 A few days ago I noticed my anti-freeze was a little low, so I filled it up.  A few days later the computer told me to check the coolant level, so I did and found it was a little low again.  This time I filled it up, but cross threaded the cap and was in too big of a hurry that day to notice.  Later on that day on my way to work I started to smell anti-freeze coming through the a/c vents, so I checked my gauges and realized my temp. was climbing.  I pulled over and checked it and there was radiator fluid coming out of the expansion tank where it has been cross threaded.  I let it cool down till I got off work (about 6 hours) then added some more anti-freeze and tried to drive it home, but after about 5 minutes of driving the temp. started to climb again.  I had my dad help me tow the car home because I didn't want to drive it hot and create even more problems then I already had on my hands.  The following day we replaced the thermostat... tried driving it... and it overheated... again.  Today we replaced the water pump, but now we can't seem to get the anti-freeze to circulate through the radiator and motor.  We tried letting the motor run for a few minutes, but it didn't suck any of the anti-freeze out of the expansion tank and into the motor.  I'm not sure what step to take next.


I know this is a lot of stuff to read over, but any would be greatly appreciated!

Thanks,
Mike

Answer
Mike,
 Unfortunately I am not an "expert" on the E36 3-series.  I do own one, but I'm still learning about them.  I am more familiar with the E30.  
 I do know that there is a bleed screw on the expansion tank, right beside the filler cap (that you cross-threaded).  Take a large screw-driver and open this cap a little, and you will hear air coming out of the system.  

 What is happening, is that air is trapped inside the engine or somewhere else in the system, and it's keeping the coolant from entering.  I would open this bleed screw slightly, start the engine and turn the heat as high as it will go, inside the car.  This will allow coolant to flow into the heater-core and flush air out of there as well.

 Once the engine is started, you will notice a small ammount of coolant running out of this bleed-screw.  Its fine, just watch for bubbles coming out.  you can idle the car up some to help remove the bubbles as well.

 I think that once you have air out of the system you will be up and running like you were.

 Good luck,
 Josh