Change it out! wasn't that bad once all the parts came in to do it. and I've never worked on a bmw before. a little messy but doable. lucky for me it was -5 out when my tank exploded down the side so when i noticed the temp going up was able to park and get a tow. seems perfect now it's been about 1500 miles and no loss of fluid or leaks so pretty happy for that (thanks Breiwa1 for the help!!) at the same time we installed cross drilled and vented rotors on all 4's ceramic pads new sensors , and new tires .. thing rides sweet! car had 113k on it when it failed and got new rad,hoses,sensors,tstat all for about 300 the pump had been replaced before so didn't feel the need.
and in total about 4 hours to do it 1-1/2 dis-assembly and 2-1/2 to put it back together ..