What Causes a Hydraulic Pump to Lose Pressure on a Dock Leveler?

A dock leveler is a piece of equipment that bridges the gap between the dock and the truck’s trailer bed. It is typically used during unloading and loading. The leveler operator can raise the machine and extend its metal plate “lip” in order to form a seamless ramp onto the truck.

Hydraulic dock levelers are one of the most common types of levelers. Hydraulic dock levelers are operated by pushing a button, whereas manual dock levelers require the operator to use a pull-chain. Hydraulic dock levelers use hydraulic pumps to automatically lift and place the leveler and lip. 

However, hydraulic dock levelers can have issues with losing pressure. This article will explain what causes this, what to look for, and how to troubleshoot these issues. 

How to Test the Hydraulic Pump

If a new hydraulic pump is installed and has trouble building pressure, the shaft could be rotating in the incorrect direction. If pressure does not build, the relief valve or pump compensator could be bad. Before checking these components, verify that the pressure at the outlet port is 0 psi. The relief valve and compensator can then be disassembled and inspected for contamination or worn or broken springs.

You can perform the following tests:

1. Check the tank line temperature of the relief valve.
2. Install a flow meter and check the flow rate.
3. Check the current on the drive motor.
4. Ensure the compensator is above the maximum load pressure.

Performing these tests should give you an idea of the condition of your hydraulic pump.

The following issues may cause the relief valves to have low pressure: 

• Incorrect adjustment.
• Dirt or small debris is holding the valve open.
• Poppets are damaged or worn out.
• Valve piston is sticking.
• Valve in the body is cocking.
• Spring ends are damaged or worn out.
• Spring is weak or diminished.
• Balance hold is blocked.

The following issues may cause the relief valves to have no pressure:

• Balance hole is clogged.
• Valve has a loose fit.
• Valve in the body binds.
• Spring is worn out or broken.
• Dirt or small debris is holding the valve partially open.
• Poppet is worn out or damaged.

The following issues may cause the pressure reducing valves to have erratic pressure:

• Oil has dirt in it.
• Balance hole is plugged or restricted.
• Poppet is worn out.
• Drain line does not open to a reservoir.
• Spring  ends aren’t square.
• Valve has the wrong spring.
• Valve could use an adjustment.
• Spring is fatigued.
• Spool bore is damaged or worn out. 

Contact Us Now

Parts Brite can assist you with your hydraulic dock leveler maintenance needs. We are proud to provide a wide variety of state-of-the-art aftermarket dock leveler parts. We have the parts that your docking business needs. 

While our sales office is in southern California, we have distribution centers in both Wisconsin and California.   Call now 1-855-PARTSBRITE (1-855-727-8727) to learn more about how we help.