Turns out is was the cap. The tank was replaced in 08' with the original cap. The cap we tried yesterday was also bad. No gasses were found in the coolant. $33, LOL. Thanks everyone, olsusana.

Thanks everyone, will post what is determined.

Thanks for the time!

My 1999 V70 Turbo Wagon has 156,000 Mi. The low coolant light came on so I fillled the expansion tank to max level. I started looking for leaks and found it would leak coolant after shutdown thru the expansion tank cap. It doesn't overheat. Runs fine. Tried a different cap, same problem. There appea...