To check for air leaks in the shift tower, unplug the two airlines from the air cylinder on the pump. Cap off the air, be sure not to mix up the proper fittings lines came out of. After capping off ends, operate the up/down control to confirm if air leak stopped. If air has stopped, O-rings in cylinder or pump may need to be replaced. If valve still leaks then O-rings in shift tower may need to be replaced.