1/2" is way too big, 3/8" is iffy due to the tight quarters between the housing and block 1/4" works great. Yes, you'll have to drain the coolant, but you don't even have to remove the lower radiator hose if you're careful. Just the 3 bolts and off comes the housing (still attached to the hose), swap t-stat and o-ring, put the housing back together top off with coolant and water.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.