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Bleeding a Gravity Tilt Trailer Hydraulic System
#1
Purpose of Bleeding
Bleeding the hydraulic system of a gravity tilt trailer is essential to remove trapped air that can cause jerky or erratic tilt deck movement. Air in the hydraulic circuit reduces efficiency, causes delayed response, and may damage components if not expelled properly. Ensuring an air-free system stabilizes operation and prolongs hydraulic component life.
Typical Components Involved
  • Hydraulic cylinders controlling the tilt deck and reservoir cylinders.
  • Hydraulic pump, often a dedicated external unit such as the KTI DC-4442.
  • T-fittings on cylinder hoses providing connection points for bleeding hoses.
  • Valves or taps to open the system for fluid circulation during bleeding.
  • Hydraulic fluid (non-foaming) to refill and replace displaced air.
Bleeding Procedure Summary
  • Attach hoses from the hydraulic pump’s outlets to the T-fittings on the hydraulic cylinder at the tilt deck’s top and the reservoir cylinder at the bottom.
  • Open the system’s tap or valve to allow fluid circulation.
  • Engage the pump’s "UP" control to raise the tilt deck fully until the pump stalls, indicating the cylinder is fully extended.
  • Without closing the tap, use the "DOWN" control to retract the deck fully until the pump stalls.
  • Repeat the up and down cycles approximately 5-6 times to push trapped air out.
  • Lower the tilt deck fully and let the system rest for 2-3 minutes to allow remaining air bubbles to escape.
  • Remove hoses, top off hydraulic fluid, and reinstall protective caps on fittings.
  • Cycle the deck up and down to verify smooth, responsive operation.
Key Tips
  • Use non-foaming hydraulic oil to avoid introducing new air bubbles.
  • Ensure hoses are tightly connected but only finger-tight to avoid damage.
  • Conduct bleeding in a clean environment to prevent contamination.
  • Carefully monitor fluid levels throughout to prevent cavitation.
Glossary
  • Bleeding: The process of removing trapped air from hydraulic systems.
  • Hydraulic Cylinder: Device converting hydraulic fluid energy to mechanical force.
  • T-Fitting: Plumbing component allowing fluid or air diversion/access.
  • Reservoir Cylinder: Auxiliary hydraulic cylinder maintaining system balance or fluid storage.
  • Pump Stall: Condition where hydraulic pump meets maximum resistance indicating full cylinder stroke.
Additional Resources
Informational videos from manufacturers and supply companies detail step-by-step bleeding procedures, often specific to model trailers such as PJ or Load Trail gravity tilt trailers. Utilizing manufacturer-supplied equipment and following recommended sequences ensure effective air removal and system reliability.
Conclusion
Bleeding is a straightforward but essential maintenance task to ensure gravity tilt trailer hydraulic systems function smoothly. Methodical cycling of hydraulic fluid through the system using dedicated pumps, proper hose connections, and fluid management restores hydraulic circuit integrity, enabling safe and efficient trailer unloading.
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