[RawhideKid]

Mr. J
Cleaning the cooling system with the radiator in the car only helps promote the loose rust from the engine to circulate and stick in the top and tubes of the radiator.

If you want to clean the system out, remove the radiator, lay it flat on the front, leave the cap on, pour a gallon of vinegar in and let it set for a couple days, you can agitate it by gently sloshing the fluid toward the top.

After a few days of soaking, drain the contents through a strainer of cheese cloth and see how much rust is removed. I then pressure blow water through from the bottom to the top.

The engine is another story. What I did to mine was, since I had to replace the head gasket, while it was off, I used a bore brush on the drill motor and swept the insides of the water jacket, specially around the #3 and #4 cylinders, then with a magnet, cleaned up the rust. If you use vinegar it will continue to eat away at the metal, so DO NOT use that in the engine. I suppose you could use evaporust or some such remover, but please do it while the radiator is removed from the car.