Chrysler Repair: No heat in 95 Concorde, automatic climate control, copper tube

Question
Hi,
I bought a 1995 Concorde with only 55,000 miles in 2005. Car has the Automatic Climate Control. First winter heat worked fairly well. Last winter no heat. Checked heater core temps and inlet and outlet were within 10 degrees of each other. Flushed the system. Heat worked for about a month then nothing. No error codes showing up on the ATS. One garage replaced the Heater core. I cut up the old core and found what looked like springs in every copper tube. I thought they may have left production tube bending fillers in and forgot to remove them after bending the tubes. If they are in there for a reason the resulting hole through the center is only about .090" in daimeter and would be very easily clogged. The new core worked for about 3 weeks then heat faded to nothing again. Assume clogged again maybe from residual "gunk" in the system. Got in touch with the original owner and she said she had the water pump replaced 3 different times and the heating system flushed at least 5 times for the same reason. What could be clogging the system so quickly and repeatedly? Thanks.

Answer
old engine  it just happens the coolant used brakes down stuff  and eats away things. If u had a clog then one side of the heater tubs would be hot and the other colder. And u say flush the system  do u mean taking it to a shop where they attach it to a machine and suck out the old stuff and have fluid that will clean out clogs  or was it just a drain and fill??