Removing Rust from Cooling System

[Luva65wagon]

Just be careful not to get water down the oil holes...

[BPVan]

I heeded all warnings. I carefully flushed the block and radiator with hot water until it came out clear. I am going to pull the thermostat housing and water pump to carefully clean them, run hot water through the heater core, then call it good until reassembly. The freeze plugs look good and all else seems to be checking out.

[Luva65wagon]

Hmm... and all this time I thought your motor was pretty new. Not sure why I thought that, but the picture would indicate otherwise.

That looks pretty normal for water-only coming from a block. Left there overnight fresh water would do the same. Lots of raw cast-iron in the water jackets. Takes no time at all to turn brown. That's why you add green.