Originally Posted by Coolerking
Perhaps a dumb question but I'm assuming that to drain out / replace the antifreeze in a closed loop coolant system (on a salt water series LY6) you just remove the petcock or drain
plug from the lower side of the engine. Let the antifreeze drain out, replace the plug and then top it up again from the expansion tank?
Not sure about the LY6 but when I drain my GM 275hp TBI cooling sytem there are two drain plugs for the block, one on each side. port side is a plug, starboard side is a knock sensor. Pulling only one plug will only drain one side of the block.