It's funny you mentioned "broke loose chunks." The previous owner of my truck seized up the original 01 engine and replaced it with a newer 80k mile salvage motor.

When cleaning up things under the hood, I grabbed the heater core feed line to move it and it crunched. Before I realized how stupid of a thing I was doing, I squeezed it a few more times then moved over to the other hose and did the same thing.

After pulling the hoses I found them rotted on the inside and breaking apart pieces. ..probably jamming them into my system.

No issues yet but I'll be tearing it all down soon anyway for the forged bottom end, cams and blower. :0)

Long story short, The hoses could look fine on the outside but be corroded on the inside.

 

I agree with about all of the above. A thermostat is cheap and motorcraft is your best bet since changing it would eliminate one possible cause of your probem. Also check your water pump. The impellers might be rusted off and you are not getting the circulation you need. Also, there is a good chance that some of the rust you had in your cooling system broke up when you flushed it and it is now blocking the flow of water. As a result, your heat is sporatic because of the blockage. I would reflush your system and make sure you take out the drain plugs in the block to get out all the rust.

 

Well I took out the t-stat and drove for 45 minutes and no issues. I got a little above C but not much (it was 40 degrees out). Still doesn't have the greatest heat, but it's blowing warm air. Before I ran it without the t-stat the coolant reservoir was as green as can be and after it was dirty brown. Don't really understand that because I flushed it with water 3 times in August so I would have thought all of the crud would have been gone.

 

Must have a bad thermostat. Hey a brand new one, and flush the block. Don't just replace the coolant, flush it with fresh water. Full with coolant and distilled water and your corrosion should stop for a while. Gotta make sure the system had no air in it.