An SKF SYSTEM 24 automatic lubricator unit shows air between the grease and the piston, is this due to air bubbles or gas leakage by the gas cell?
Most likely the SYSTEM 24 unit could not dispense the grease due to perhaps a blocked feed line, which was discovered rather late. When SYSTEM 24 reaches its time setting, gas production stops. The gas will start to diffuse through the plastic housing (same effect as in an old fizzy drink bottle). Due to the vacuum behind the piston, it will slowly return to its original position. Visually this looks like air between the grease and the piston, but it really means that the piston has started to climb back to its original position. In that case, SKF recommends clearing the grease feed lines with a grease gun, installing a new SYSTEM 24 unit and replacing it in time.
