1999 Chevy Silverado Dorman heater hose

I would replace the quick connect hose adapter with a simple nipple. Mine was leaking the other day so I went to replace it with one from the store. The cheap metal alloy connector broke off on the manifold. Antifreeze weakens the alloy and makes it brittle.
If this happens take a small rag with a fish hook stuff it in the manifold hole. Keeping the metal bits from falling into the engine. Use a chisel to lightly break the alloy from the threads. use a tap to clean the threads. Then but a simple nipple w/ threads from any auto parts store. Cut the metal end off the heater core hose and attach w/ screw clamp. problem solved and cheaper then buying the hoses and adapters from GM.
I hope this helps.