My 2000 s10 pickup has low to no heat. Had garage flush out. Was told needs a new radiator because the old one was filled with junk. Put in new radiator and thermostat $400 - still little to no heat. Garage flushed out again, ran cleaning fluid through and checked the water pump. They then told me the heater core was plugged and I needed a new one. After they put in a new heater core for 800$ I had full heat for a few days then back to little or no heat. Called garage and was told fluid might be low. Checked fluid and it was not low (I was able to add about 1 cup of antifreeze). The line going into the heater core is hot the one coming out is cold so its not circulating. It seems like my new heater core is plugged or there is a air lock. I'm not sure if I should bring it back to the same garage so they can not fix it while maxing out my credit card. Was thinking of taking it to a Chevy dealer to see if they can find the problem. Any suggestions would be greatly appreciated.