95 Roadmaster, nasty heater core, FIXED

Problem:
Heater lines getting hot but no heat to the cab. T-state good. Heater controls good. Air motors good. Unhooked heater lines before and after core. Nasty black flakes and gunk. Flushed out core in both directions until water is fairly clean. Reattached hose, filled to proper level and ran vehicle. While running for 5 min., temp gauge on dash rose to the first white line. Put a thermomitor in middle vent. Temp read 110 degrees while heater control set at 90 degrees (highest position). Will do a complete flush with Prestone if weather permits...

YEA BABY...Problem solved....Nasty heater core..............

Greetings,
I have had the same problem on 2-1995 BREW cars. Flushed twice and problem returns in 1-2 months. Material is solid and not metallic. Finally installed a Brass 1/2inch Y trap in-line with heater inlet hose. Now I can empty material from trap without removing heater core. After 2 months I got out another 1/2 oz. This time without loss of heat. Still checking with GM on source of material. Suspect some kind of block coating for rust prevention? Let me know how your progress. I have a procedure for heater core removal. Thanks Dick M.