In normal operation the master cylinder splits the flow of the oil and routes the trapped system oil to each side of the planter. The individual wheel lift cylinders are not at the end of there stroke in either the raised or lowered position. This allows the wheel modules to walk independently of each other for a smoother unit ride. When the doughnuts are taken off the front of the master cylinder rod internally the two pistons inside the barrel uncover bypass ports and by holding the control valve in the raise position pressure will extend the wheel cylinders all the way up against internal stops inside of them. Now the trapped air can be bled off. Lower planter and reinstall the doughnut stop and should be ready to go. If the planter soon gets un level again a master cylinder reseal is in the future. Hope this helps.