hello all.. we just bought an 05 outback 3.0r vdc ..car has 161k looks like 60k 1 owner ect... in town temp is normal .. wife and i went for a drive 30 miles on interstate and then back another 30 miles on way back car was running verry hot did not go to red bar but the bar before .ran heater on high ..no white color in oil or cap.. exhaust tips look fine no extra oil build up exc... was told to drain coolent and add gallon of amonia and water/coolent let car run for a an half to hour set over night then drain and replace with new coolent .. rad cap has small green slime buld up. fans seem to pull air ok .. is this the correct way to flush and clean radiator ? any sugestions ???