I have a 89 Deville 142000 miles on a 4.5L . I don't know the history of this car. After driving 2-3 miles the Engine Collant/ Fan light comes on. At that point the upper radiator hose is real hot & rock hard, the filler cap is cool to the touch, if I open the filler cap about 1/8th of a turn hot coolant blast into the overflow tank. Do I start with the radiator first or flush the entire system first ? What about the thermostat ?
PS. The coolant fan is working. Any pointers? Thanks Dave