assuming you mean flush and not abrupt, I drain all the coolant. Some say you need to use distilled water, Idk, I just run my hose through my radiator with the drain plug open until it comes out clear, then let it drain. Then I flush the heater core by putting a hose on either end (pull the hoses off the fire wall) and flushing it until it's clear. Some people pull the freeze plugs. I've put the hose on the water pump and ran till it came out of the intake clear. That's the thing, just emptying all the old coolant and funk. You can run a radiator flush through it as well if you want.