Im thinking its heater core time

[ARogg619]

I'll be the snake-oil salesmen "blue devil" it works just be sure to follow the directions properly,
they have 2 different kinds.
1. you leave in
1. you use once then flush it out
I used the one you leave in. It's not cheap the 2 bottles will run you about $65
good luck!

you might also try swinging by a dealer and ask for some "cadillac tabs"

i actually just bought those "AC Delco sealing tabs" online. Gonna try those first since it was only 6 bucks lol. Just need to find the time to throw them in and let the truck run for a while with the heat on. Im hoping I can just throw them in the overflow since we dont have a radiator cap and i dont wanna pull a hose off. The truck has been pretty ok as long as the AC is always on but it definitely needs to be addressed.

 

[ARogg619]

I'll play the devil's advocate... what if it's NOT the heater core? Are you going to have any diagnostics done before pulling the trigger?

This mechanic always does diagnostics first. He then makes his recommendation on work to perform but he said from what im telling him, its almost definitely a small leak at the heater core.