When you say slushy, was it freezing? As far as the flush, it isn't hard to do. Basically, you drain the radiator (drain on bottom of radiator) and place a product (flush) in it and spray it through using a garden hose. Please review the directions on the bottle when you get it because there are so many different brands, they all seem to have a different way to use it.
I would like to recommend a couple things. Remove the upper radiator hose and the replace the thermostat. They are under 10 dollars. Also, while the thermostat is out, flush the engine block too. Also, remove the heater core hoses and spray water through each hose (both directions to back flush).
When you are all finished, make sure to mix the new coolant 50% coolant and 50% water. Also, if you have water in it now and live in an area that is below freezing, get the water out ASAP or you will end up with other problems if it freezes.
Let me know if you have questions while you do it, and Happy Thanksgiving!
Thursday, November 25th, 2010 AT 5:56 AM