How to Properly Bleed Air from a Dump Truck Cylinder

Published: March 4, 2016 Last Updated: July 20, 2021 Industries, How To Series, Waste

Trapped air can contaminate the hydraulic fluid in your system and affect overall performance. For this reason, bleeding air from dump truck hydraulic cylinders should be part of your regular maintenance program and performed before installing a new hydraulic cylinder.

Bleeding dump truck hydraulic cylinders involves bringing air to the top of the cylinder, then releasing the trapped air. The process varies slightly depending on the type of cylinder installed and whether you have a bleeder valve on your dump truck cylinder below.

Follow the steps for your cylinder type below to bleed air from a dump truck hydraulic cylinder properly.

Bleeding Air From Single-Acting or Lift Dump Truck Cylinders

  1. Raise the dump body and cylinder to full extension. Leave the dump body in this position for several minutes to allow air to rise to the top of the cylinder.
  2. Lower the dump truck cylinder until the front of the dump body is approximately 2 feet off the chassis frame.
  3. Put the body up lever in the center/hold position.
  4. If your dump truck hydraulic cylinder has an outside bleeder valve, crack the valve open. If the bleeder valve is located on top of the cylinder, use a wrench to remove the dog box cover and move it to the inside of the dump body, then crack the bleeder valve open.
  5. Wait until all trapped air has escaped from the valve and a full stream of hydraulic oil is escaping from the valve.
  6. At this point, the cylinder is bled, and the bleeder valve can be closed.

Bleeding Air From Rod Type Hydraulic Cylinders

Before releasing air from the dump truck cylinder, make sure the hydraulic cylinder is not pressurized in any circumstances. The bleeder valve should be pointing upwards when the hydraulic cylinder is positioned horizontally. The piston rod must be in a fully retracted position at first.

  1. Open the air valve at the upper side of the hydraulic cylinder.
  2. Check all hoses or pipes the sure they are connected properly.
  3. Set up the hydraulic system and start it up.
  4. Extend the piston rod slowly with no pressure built up. Keep extending the piston rod until there is oil/foam coming out of the air valve. (Hydraulic cylinders that go over-center must be air-released before mounting in the construction!)
  5. Shut down the system and close the air valve.
  6. Depressurize the system before opening the air valve at the lower side of the hydraulic cylinder.
  7. Startup the hydraulic system.
  8. Retract the hydraulic cylinder slowly with no pressure built up. Keep retracting the dump truck cylinder until there is oil or foam coming out of the air valve.
  9. Shut down the system and close the air valve.
  10. Retest the hydraulic cylinder by extending and retracting the piston rod until it is running smoothly.

Refilling Your System with New Hydraulic Fluid

Refilling your system with new fluid after bleeding air from your dump truck cylinders will further improve performance.  Always use clean, high-quality fluid with the right viscosity to ensure your cylinders operate smoothly and efficiently.

Help prevent hydraulic system contamination by only using fluid that has been stored properly. Other fluid contamination prevention measures include installing fluid bypass filters and replacing worn valves and components during preventative maintenance.

At Hydraulic Cylinders Inc, we have the product & knowledge to serve you in choosing the right dump truck cylinder for your equipment. Contact us to discuss your hydraulic cylinder needs or explore our blog to find answers to common hydraulic cylinder maintenance questions.