Hey guys, I ran upon a 2005 Yukon Denali with 87k miles on it and bought it the other day. Yesterday when we got back from goofing off I parked and come out to coolant all over the ground. I can drive it with and temp never gets hits 210* . Truck DOES NOT over heat. When I park it empties coolant reservoir with engine off. It has a new water pump. I'm at a loss. Any ideas? Well 20 min later and I may have found it. My coolant tank is leaking from bottom. I'll fix that and report back.

 

Update and solution. Problem solved. Coolant reservoir tank had a crack that opened when hot.