Pull the t-stat and you can do a flush in 5 min. and the engine never gets hot enough for the next batch of fresh water to hurt it. 5 flushes takes a long time with the t-stat out and a lot longer with it in. For the drain I, 1st open petcock, 2. pull lower hose and 3. pull block plug on drivers side. Reverse procedure for next flush. Do 5 times with distilled water and the last flush will look like you can drink it.