drive it around until the thermostat opens up then pull the upper radiator hose off the thermostat cover then stick a garden hose in there and flush it until the water comes out clear or until the thermostat closes up. Then put the hose back on and drive around for a little while then do the same thing. Do this 3 or 4 times then pull the lower radiator hose to drain the water and add a gallon of coolant to your system and then fill the rest with water and you'll have most of the crap out of it.