How to---------???

Hello, i have a 1980 deville, 368, I would like to drain cooling system,I heard if you disconnect small hose near top of rad ,right behind the filler hole and put a garden hose into it ( the small hose) that this works good,would the thermostat stop the flow from getting into the block?.tnx

That will not work, put a flush port in one of the heater hoses.