Stop in for a cup of coffee

Block seems to be much cleaner now. Started on radiator. Filled with vinegar, rad laying flat. Filled through lower outlet, had most of vinegar poured out of bottle and top tank was still dry, near zero flow. Poured it out three times and got sediment every time. This last one is with some more simple green.
Its getting better. I put a heater on one end now, see if heat changes anything.