every other week something new

[1iwilly]

quick recap
in oct 2016 change water pump then 1 week later radiator upper neck crack
put in new radiator. 3 weeks ago change tstat as the housing was leaking coolant since the it has
been running fine then today bam it over heats. WTF got code for coolant temp sensor low input something like that gauge peg in corner.got it tow home
4 hours later re-fill cooling system took 1 3/4 gallons did the bleeding all seems good drove it for 5 minutes came back took cap off coolant a tad low but no leaks what so ever
the only thing i saw is from time to time coolant work come out from radiator cap even though it was tight. so where is some of the coolant going if not leaking or smoke from tail pipe