Cause / 307
1. Low on oil. 2. Too much oil. (Plus water in oil from air line.) 3. Improper grade of oil. (Foaming) 4. Leak in interior air line. 5. Baffle tube in tank out of position. 6. Lift not raised to full rise often enough to allow automatic bleeder to operate. (Semi-Hydraulic) 7. Check disk on bottom of plunger broken apart.
Repair / 307
1. Locate and repair source of oil loss. Add oil. 2. Check level, siphon excess. (Install water trap near control valve.) 3. Change oil. 4. Replace lift. 5. Center and reseat tube. 6. Daily raise the lift to full rise or manually bleed the lift. 7. Install replacement check disk or replace plunger.