It's not antifreeze, I guess I should have been more specific, it's just white un-burned diesel smoke... I don't know enough about these engines to diagnose them. It runs well enough, and doesn't burn much oil, so I don't think it's just to worn. It will run all day long with no problems except the smoke. I don't have a good Detroit mechanic around (as far as I can find out) or I would just have them come out and take a good look at it.
Thank you all for your help.
P.S. if it is worn out, does anyone have an idea of the material cost of an in-the-tractor overhaul on that engine?