I just submitted a question about leaking antifreeze. Maybe this will make it ea

the water pump will cause me to lose antifreeze?

Yep, when it leaks it will, every time!!! Check radiator also. Look very close, hard to find at times..even under pressure test!!

Like pushrod said, we can see the water pump leaking from here! GM 5.3L = Water Pump leak!

Bypassed the Heater Core. No more leak.

Ok. No more heat either but you wont need that for awhile!

Nope not in Houston, TX! 104 yesterday.

Crap! Ac ok? These 5.3 engines are just famous for mystery H20 leaks and most of the time it's the pump or rad. A little unusual for the core to leak. When you get it fixed use good old fashion antifreeze, not Dexcool.

A\C blows artic cold. I was told I had to use Dexcool and not to change it. What's up with that?

That is just a bunch of B.S.!! After working on these GM vehicles and seeing the effect of Dexcool, first thing i did, after warranty, on my Blazer is flush that crap out and replace it with the old green stuff. Google Dexcool, look around a bit and you will see, i think. Probably the reason your heater core is leaking!