Anyone tried this, my neighbor told me he's done his coolant flushing 1. Drain the radiator then plug it 2. Disconnects upper radiator hose and points it downward to a catch pan/bucket 3. Puts running water hose in radiator top filler but he doesn't "seal" it to create any kind of pressure just wants full, free flowing water going into the radiator 4. On a cold engine he turns the engine over/on for a few seconds to allow the water pump to push out all the old coolant. He says the engine will never approach anything dangerously hot as it just runs for a few seconds, long enough to pump out all the old fluid. He then does his chemical flush with only clean water being in the engine. The reason he says he does it this way is any residual coolant left in the system will retard the cleaners in the chemical flush. I asked him what about the heater core, he said he flushes that out with a final distilled water flush after the chemical clean just prior to adding his premix and doesn't worry about flushing the heater core with a chemical flush because if the chemical flush creates a leak in the heater core, it's expensive/time consuming to replace it. He said he would only ever run a chemical flush through the heater core if he saw that his cabin heat was no longer getting as hot. Any thoughts? Unless I'm missing something, and it's very possible I am, it seems like a legit method.