Summary of Common Malfunctions of Manual Hydraulic Forklifts

1、 Hydraulic system malfunction

Forks cannot be raised or raised slowly

reason:

Insufficient hydraulic oil or deteriorated oil quality (such as impurities or air).

Improper adjustment of the oil drain valve (due to tight top thread or internal leakage).

The wear or aging of the pump core plunger and oil seal leads to insufficient pressure.

Hydraulic cylinder leakage (excessive clearance between valve body and cylinder, damaged seals).

Solution:

Check the hydraulic oil level, replenish or replace clean hydraulic oil (recommended ISO VG32).

Adjust the top screw of the oil drain valve to the appropriate position, or replace the valve core.

Clean the internal dirt of the hydraulic system and eliminate air (by repeatedly pressing the handle to exhaust).

Replace worn pump cores, oil seals, or hydraulic cylinder seals.

Forks automatically descend or cannot maintain height

reason:

Impurities in the hydraulic oil prevent the drain valve from closing.

Seals (such as oil seals, O-rings) are worn or damaged.

The safety valve spring has failed, and the system pressure is below the specified value.

Solution:

Replace the clean hydraulic oil and clean the inside of the valve body.

Replace aging or damaged seals.

Adjust or replace the safety valve spring to ensure normal system pressure.

Hydraulic system leakage

reason:

The seals at the connections of the oil cylinder, valve body, or pipeline are aging.

Parts cracking or wear (such as cylinder body, piston rod).

Solution:

Replace the seal at the leaking location.

Check and repair cracked or worn parts, and replace the cylinder block if necessary.

2、 Mechanical structural failure

Arm deformation or fracture

reason:

Long term high load use or improper operation can lead to metal fatigue.

Solution:

Weld reinforcement for minor deformations.

When it breaks severely, the pull arm needs to be replaced.

Unbalanced fork arm

reason:

Deformation or wear of the pin shaft (such as at the connection between the square connecting rod and the wheel fork).

Solution:

Replace the worn pin shaft.

Adjust the length of the square connecting rod (right-hand shortening, left-hand lengthening) to balance the fork arms.

Nylon roller and fork malfunction

reason:

Roller detachment (elastic pin worn and broken).

Bearing wear or fork deformation (long-term heavy pressure or lateral force).

Solution:

Replace the elastic pin or bearing.

Heat and correct the deformed fork (using gas cutting flame to heat and apply inward force).

3、 Steering and operation malfunction

Steering wheel stuck or making abnormal noise

reason:

The bearing is damaged or the axle clamp spring falls off.

Solution:

Replace damaged bearings or retaining springs.

Malfunction of oil drain valve handle operation

reason:

Improper adjustment of gap between hard or soft connections.

Solution:

Adjust the connection gap, or directly replace the top screw of the oil drain valve with a long bolt and operate with foot pressure.

4、 Other common questions

There is air in the hydraulic oil

Phenomenon: The fork rises slowly or shakes.

Solution:

Place the forklift on a level ground and repeatedly press the handle to exhaust (about 10-20 times).

Seal aging

Phenomenon: Hydraulic oil leakage or insufficient pressure.

Solution:

Regularly replace seals (the lifespan of oil seal repair kits varies depending on the brand, with imported parts typically lasting 3-5 years and domestic parts lasting several months to 2 years).

Valve body wear

Phenomenon: Hydraulic oil leakage, weak or automatic lowering of forks.

Solution:

Chrome plated and polished the slightly worn valve stem.

Replace the valve body or stem when it is severely worn.

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