Forklift Mast Drops While Lifting Load – Causes and Solutions

Why Does the Forklift Mast Drop While Lifting?

One of the common issues during forklift operation is the forklift mast (hydraulic cylinder) dropping while lifting a load. This problem affects productivity and can pose safety risks. Let’s explore the main causes and how to fix them effectively.

1. Worn or Damaged Hydraulic Cylinder Seals

The seal (or gasket) keeps hydraulic fluid pressure inside the cylinder. When the seal is worn or damaged, fluid leaks, pressure drops, and the mast slowly lowers. This is the most common cause.

➡️ Solution: Disassemble the cylinder, inspect and replace seals as needed.

2. Leaking or Stuck Hydraulic Valves

Control valves such as lowering valves or check valves may become stuck or worn, causing hydraulic oil to flow back, reducing pressure and causing the mast to drop unexpectedly.

➡️ Solution: Inspect the hydraulic valve block, clean or replace parts as needed.

3. Low or Contaminated Hydraulic Oil

Insufficient oil or oil contaminated with dirt or air reduces pressure and fails to hold the load.

➡️ Solution: Refill with proper hydraulic oil, replace oil regularly, and bleed air from the system.

4. Worn Hydraulic Cylinder Bore

Over time, the cylinder bore may wear out, reducing sealing efficiency and causing internal oil leakage.

➡️ Solution: Re-machine or replace the cylinder.

5. Leaks in Hydraulic Hoses or Fittings

External leaks in hoses or fittings can also reduce system pressure, causing the mast to drop.

➡️ Solution: Check and tighten or replace damaged hoses or connectors.

How to Prevent Forklift Mast Dropping

Perform routine inspections of the hydraulic system (seals, valves, oil).
Use quality hydraulic oil and replace according to service intervals.
Avoid overloading the forklift.
Follow manufacturer maintenance guidelines.

FAQ

1. Is it dangerous if the forklift mast drops while lifting?
➡️ Yes. It can cause sudden load drop, putting the operator and nearby workers at risk.

2. Can I replace the hydraulic seal by myself?
➡️ Not recommended unless you are experienced. Seek help from a trained technician.

3. How often should hydraulic oil be replaced to avoid pressure loss?
➡️ Every 1,000–2,000 working hours or as advised by the manufacturer. Replace sooner in dusty environments.