I noticed a water sloshing sound behind the dash when first starting out for about a month. I didn't get any warning lights or notice anything leaking under the car but when I checked under the hood the coolant reservoir was empty. I made appointment at GM dealership and they found I had a leak along the side seam of my radiator. The car only has 61k miles! I found online that GM has noted a structural design issue in my XT6. The radiators were engineered with tight thermal break tabs. If they stay locked in place...
Read the full complaint
they trap immense physical stress during engine heat cycles and force leaks along the seams. This appears to be what happened. If it had occurred while we were on a trip and totally failed while on a highway, I can imagine the result could have been catastrophic. I have contacted GM.