I had almost the EXACT same problem yesterday. It is all explained here
AOS replaced. Now Coolant Leak.
I found the new coolant cap with the part number ending in .04 that I ordered over a year ago and put it on. I don't think that that is going to fix my problem because I have coolant all over my driveway. Most likely going to be the whole coolant tank for me. I will know for sure when I have time to peel back the carpet in the daylight. I hope your solution is easier than mine.