At Saijuki Engineering, a specialist construction machinery and heavy equipment repair shop located in Kumagaya City, Saitama Prefecture, the most common requests we receive are for repairs related to oil and hydraulic fluid leaks. In this article, we will introduce common areas where oil or hydraulic fluid leaks occur, and we hope you will use this information for your pre-operation inspections.

Construction machinery and heavy equipment run on oil and hydraulic fluid

Construction machinery and heavy equipment run on oil and hydraulic fluid.
It is no exaggeration to say that oil and hydraulic fluid are used throughout the machine, not only in critical points but in many areas.

Where it bends, extends and retracts, or rotates—any moving part involves oil or hydraulic fluid.
We will now introduce these areas in detail. Checking them during routine pre-operation inspections, or when you feel something is not moving smoothly, can help you detect issues early and enable simpler, smoother repairs.

Oil leaks from hydraulic cylinders

One of the most frequent repairs for construction machinery and heavy equipment is oil leakage from hydraulic cylinders.
Hydraulic cylinders are used in many types of machines, such as excavators, forklifts, and dump trucks, and they are fundamental to all kinds of work, including excavation, transporting building materials and supplies, grading, scrap handling, and mowing.

Causes include oil leakage due to wear from aging seals, oil leakage from cracks or splits in hoses, and oil leakage caused by damage to hydraulic lines from impacts when the machine is physically struck.

As a countermeasure, it is important to perform routine visual checks and not assume that “it will be fine.”

If this is difficult, requesting regular on-site maintenance from a construction machinery and heavy equipment repair company like ours can help prevent serious accidents before they occur.

Looking further into it, damage to seals caused by scratches, rust, or bending of the cylinder rod can also be a cause of oil leaks.
In such cases, our company can provide repairs at any time, including re-plating the cylinder, cylinder repair, or replacement with economical, high-quality remanufactured (rebuilt) units.

Oil leaks from the engine

After oil leakage from hydraulic cylinders, the next most common oil/hydraulic fluid leak issue in construction machinery and heavy equipment is likely oil leakage from the engine.

Causes include wear or damage to various parts due to aging.
Specifically, wear or damage to components such as gaskets, packings, piston rings, and valve seals can be the cause.

The primary measure is to replace them with new parts regularly before oil leakage occurs.
Other options include using an oil stop-leak additive or choosing a higher-viscosity engine oil; however, the parts listed above will inevitably wear or fail, so replacement before that happens is recommended.

Oil leaks from travel motors and swing motors

Because covers are often installed around travel motors and swing motors, dirt, dust, and foreign matter can accumulate inside, causing hoses to deteriorate or corrode and leading to oil leaks…

We sometimes see cases like this.

As a countermeasure, open the cover regularly and thoroughly wash away dirt, dust, and foreign matter.
That small effort alone can help you avoid needing oil leak repairs.

As this area can be costly to repair, we recommend requesting regular maintenance and cleaning from a construction machinery and heavy equipment repair company like ours to avoid expensive repair costs.

Summary

In addition, if we list smaller items, oil or hydraulic fluid leaks can occur from virtually anywhere, including hoses, swivels, and control valves.

Ideally, you would inspect, maintain, clean, and replace parts early every time, but in the reality of demanding daily work, we honestly feel that is difficult.

To put it bluntly, it is no exaggeration to say that all causes of oil or hydraulic fluid leaks are due to deterioration of consumables such as packings. Therefore, if you notice even slight seepage, we recommend having oil leak repairs performed.

It would be disastrous if your construction machinery or heavy equipment stopped working at an important job site, causing you to miss the site or significantly delay the schedule.

If you feel concerned and have found your way to this article, we would be grateful if you would feel free to contact Saijuki Engineering for consultation regarding inspection and maintenance of construction machinery and heavy equipment.