I was just saying a compression test because a head gasket might have started leaking too. Cheap and easy to check. I still believe the engine over heated causing the soft rubber gaskets to fail. If the head gasket fails completely, it will be a sudden catastrophic failure. The truck will be dead on the side of the road. I have 5 GM trucks. They all run. None leak.

If anything, get the leaking water pump replaced. A rebuilt LQ4 would be a little over $3K

https://www.monstertransmission.com/...B#.Yj95AOfMK5c