Losing Coolant Please Help!

I spung a leak in my expansion tank so i changed it but since i did i have been losing coolant with everyother start..........initially my mechanic and i thought it wasnot properly bled so we did that but its still somehow warning me that my coolant level is low every second day.
none of my hoses seem, busted and i'm mystified as to where the heck this coolant is going....a couple of times my temp started on the high side and then cooled off as opposed to the normal left to right movement.
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