glad to see I wasn't the only one who pictured some poor schmuck holding the fan with his hands and having his buddy start the car.


If the radiator is full of rusty crap, then it might be clogged up.
and if the water pump is old as balls, then it is probably going bad and you're loosing coolant through the weep holes.
A long screw driver, end on the water pump, handle on your ear, you'll be able to hear the bearings in the pump as it spins. Should sound like water flowing. But if there is a grind/crunch, then the pump is bad.

Since you say the radiator is all rusty and crap, I would want to replace it with at least a more fresh one. And try to flush out as much of that crap out of the block as possible. I've shoved a hose in one end and watched chunks of shit fall out of the other end.

Compression test might help figure out if the head gasket is bad. They can fail in such a way that a little bit of coolant gets into the cylinder but not into the oil or anything. Leak down test might be better.
Or hell, drain out the water, and fill it with antifreeze. That stuff smokes like a mofo.

Beyond that, you really gotta figure out where the water is leaking from.

does it over heat at idle?
Let it sit and run and just go over the whole thing with a fine tooth comb until you can say beyond a shadow of a doubt, there is no leak.
Many times, the heater core lines will have little pin hole size leaks in them that won't show up until the system is hot and pressurized.