Heater problem fixed!

I fought with the heater core on my G/F's 96 blazer all day last Saturday and no matter what I did, the core would not let hot water through the inlet. I finally took the hoses off and tried to blow back through outlet with compressed air. I could not get it to budge until I finally let it have all 120 psi and it finally blew back through the inlet. Next, I ran the garden hose through it for 20 minutes and could hear the water circulate from the inside of the truck (no leaks from the 120 psi luckily). Lastly I flused the radiator with the Prestone kit and refilled the system. As the motor came up to temp the thermostat open and I thought everything was great right..... wrong, no @*#@ heat! Well in one last hope of desperation, I poured a little more in the funnel and I watched coolant slowly rise up the funnel, until it farted and pushed about a quart out. I topped off again and checked the heat... awesome hot air pouring out!!! Morel of this story is the these vehicles are a nightmare for air lock, I tried driving for 2-hours with the cap loose, everything I could think of, nothing would let the air out, I even parked on a steep hill with the nose pointing up.

Just thought I would share this in case anyone is battling the same problem.

I had a car (thirty years ago) that would air lock the heater anytime the coolant got low, and would not clear without intervention. I ended up putting a straight splice at the top of a heater hose loop. When the problem occurred, I would fill up the radiator, loosen the splice and pressurize the system with a tester. When liquid came out of the splice I would lock it all up, top off the fluid and wait until it happened again.

Also, remember to replace the faulty stock rad cap that causes this problem.

Why didn't you flush the heater core? You flushed the rad, why did n't you do it too?

Also, remember to replace the faulty stock rad cap that causes this problem.

Why didn't you flush the heater core? You flushed the rad, why did n't you do it too?

I took your advise and pitched the old Delco cap and also forgot to mention that I spliced into the inlet hose with the Super Flush adaptor when I flushed it with the hose.