Extream over heating

3 months ago i replaced my radiator. The car was overheating, the coolent looked like clay sludge and the low coolent light would kick on and off randomly. After replacing the radiator i didn't have the problem untill recently. Some how the powersteering pully fell off i went less than a block found the pully and managed to put it back on no problems. Then the overheating problem came back. The Coolent is the same sludy clay color. For a while the car was fine as long as i had the heater on full blast and kept the speed up over 70mph. Lsat night the car overheated and began to stall out. Unfortunately while going up a hill on a 2 lane highway with no turn outs for 3 miles. The car puttered and chugged and then the engine temp droped to normal with the "temp" light on. The car made it almost home then stalled out in the intersection i was able to start it back up and get it home. each day the problem gets worse. I've drained the coolent and refilled and my oil level is fine although it seems watery.
In addition, when i run the heater coold air will blast out no matter how hot it gets. Then the heat will blow out and i can smell dirty water in the car and the temp will drop a bit.
is there anything i can do to keep this car on life support for a few more weeks without having to spend major $?
Please help
Thank you