Taylor Stove issue- cold water coming from return line

[Scrapiron]

Have an issue with my Taylor 750. On the return line, I'm getting cold water when I bleed it.

Water temp is 160 degrees in stove. Went into attic and both the radiator in and out valves are scorching hot to touch. Air temp from vent is warm (usual). If I let the line bleed for about 5 minutes, I will get lukewarm water.

Any ideas?