Updated: 4 September 2026
Hydraulic rams — more accurately known as hydraulic cylinders — generate the linear force used throughout excavators, loaders, forklifts, telehandlers, cranes, bulldozers, agricultural machinery and other heavy equipment.
When a cylinder begins leaking, drifting, binding or suffering rod damage, continuing to operate the machine can turn a manageable repair into a much larger failure.
Good hydraulic ram maintenance therefore focuses on rod condition, seals, mountings, alignment, contamination, hydraulic oil and the operating behaviour of the complete machine.
Quick Answer
Heavy-equipment hydraulic cylinders should be inspected for oil leakage, rod scoring or corrosion, damaged seals and wipers, worn mountings, misalignment, hose problems and abnormal movement. Repeated seal failure, cylinder drift or physical damage should be investigated rather than repeatedly replacing the same part.
A hydraulic ram or cylinder converts hydraulic energy into linear force and movement.
Pressurised hydraulic fluid acts on the piston inside the cylinder, creating force that moves the rod and the connected machine structure.
Heavy equipment uses hydraulic cylinders for functions including:
Hydraulic Ram or Hydraulic Cylinder?
The terms are often used interchangeably in everyday engineering. “Hydraulic cylinder” is the broader technical term, while “ram” is commonly used in industry to describe hydraulic linear actuators.
Heavy machinery may use different cylinder designs depending on the application.
A single-acting cylinder uses hydraulic pressure to provide powered movement in one direction.
Return movement is normally provided by:
Single-acting cylinders are useful where powered movement is only required in one direction.
A double-acting cylinder uses hydraulic pressure on alternate sides of the piston to provide controlled powered movement in both directions.
This arrangement is widely used where machinery requires positive extension and retraction.
Examples can include boom, steering, tilt and positioning applications depending on the machine design.
| Symptom | Possible Causes |
|---|---|
| Oil leaking around rod | Seal wear, rod damage, contamination, corrosion, gland damage or misalignment. |
| Cylinder drifting | Internal cylinder leakage, valve leakage or load-holding circuit problems. |
| Jerky movement | Air, contamination, valve issues, mechanical binding, flow problems or cylinder damage. |
| Repeated seal failure | Rod scoring, side loading, misalignment, contamination, heat or unsuitable sealing components. |
| Rod corrosion or scoring | Moisture, debris, damaged surface treatment, impact, poor storage or harsh operating conditions. |
| Binding or uneven movement | Bent rod, mounting wear, side load, mechanical misalignment or damaged cylinder components. |
External oil leakage is one of the most obvious cylinder problems.
Common leak locations include:
A seal may be the component allowing oil to escape, but the seal itself may not be the underlying cause.
For example, a scored rod can repeatedly damage a new rod seal every time it passes through the gland.
Look Beyond the Seal
Repeatedly fitting seal kits without checking the rod, gland, alignment and contamination can result in the same cylinder returning with the same problem.
See Hydraulic Ram & Cylinder Repair.
The exposed rod works directly through the cylinder sealing system and is particularly vulnerable on heavy machinery.
Inspect for:
Rod damage can contribute to:
Depending on its condition, a rod may be repairable, require reconditioning, or need replacement/manufacture.
A hydraulic ram that sticks or binds should not automatically be blamed on dirt inside the cylinder.
Possible causes include:
The behaviour of the machine and the condition of the mounting system should therefore be assessed alongside the cylinder itself.
A cylinder that gradually moves when it should hold its position may have internal leakage.
However, cylinder drift can also result from:
Diagnosis is important before removing or rebuilding the cylinder unnecessarily.
See Hydraulic System Troubleshooting & Diagnostics.
A hydraulic cylinder cannot work correctly if the mechanical structure supporting it is badly worn or misaligned.
Heavy plant should be checked for:
Excessive clearance or misalignment can introduce side loads into the cylinder and accelerate wear on the rod, gland, bearings and seals.
Hydraulic cylinders are primarily designed to generate force along their intended operating axis.
If the machine geometry forces the cylinder sideways, additional loads can be placed on:
Repeated rod or seal problems can therefore indicate a machine alignment issue rather than a defective replacement part.
The hydraulic fluid provides power transmission, lubrication, sealing support and heat transfer throughout the system.
Use the hydraulic fluid specification required by the machine or hydraulic component manufacturer.
Important considerations include:
Do not assume that a particular ISO VG grade is correct simply because it is commonly used in other machinery.
See Hydraulic Oil ISO Grades Explained.
Some machines require specialist or OEM-specific hydraulic oil. Using the wrong oil can cause serious damage.
Check Your Oil NowConstruction and heavy machinery often operates in environments where dust, mud, grit and water are unavoidable.
Contamination can enter the hydraulic system through:
Contamination can contribute to seal damage, valve problems, pump wear and accelerated cylinder wear.
Good maintenance should therefore include clean repair practices and suitable filtration as part of the wider hydraulic system.
See Hydraulic Contamination: Causes, Removal & Prevention.
A hydraulic cylinder depends on the hoses and fittings supplying oil to it.
Inspect nearby hose assemblies for:
A hose that repeatedly fails near a boom or cylinder can indicate a routing problem through the machine’s range of movement.
See Hydraulic Hose Routing Guide.
High-Pressure Hydraulic Safety
Never use your hand to search for a hydraulic leak while equipment is pressurised. High-pressure hydraulic fluid can penetrate the skin and cause a serious injection injury. Follow the appropriate isolation, stored-energy and depressurisation procedures before repair.
There is no universal inspection interval for every hydraulic cylinder.
The correct frequency depends on factors including:
Machines operating continuously in demolition, waste, ports, construction or other aggressive environments may require a different inspection regime from lightly used machinery operating indoors.
What to Inspect
✓ Rod scoring, pitting and corrosion
✓ External hydraulic leakage
✓ Rod wiper and gland condition
✓ Pins, bushes and mountings
✓ Hose routing and fitting condition
✓ Signs of misalignment or side loading
✓ Hydraulic oil level and condition
✓ Cylinder drift or unexpected movement
✓ Repeat seal, hose or rod failures
A professional cylinder assessment should be considered when there is:
The correct solution could be anything from a targeted repair to a complete strip-down and refurbishment.
Typical Workshop Repair Process
1. Assess the reported fault
Understand how the cylinder was behaving and how the failure occurred.
2. Inspect and strip the cylinder
The unit can be dismantled as appropriate to assess internal and external condition.
3. Inspect the components
Rod, piston, gland, bore, seals, bearings and other parts can be checked for wear or damage.
4. Determine the repair route
Damaged components are repaired, reconditioned, replaced or manufactured as appropriate.
5. Reassemble the cylinder
The cylinder is rebuilt using suitable components for the application.
6. Complete final checks
The repair is checked as appropriate to the cylinder and scope of work before return to service.
A damaged heavy-equipment cylinder does not automatically need replacing.
The decision should consider:
Older or specialist cylinders can sometimes be practical refurbishment candidates, particularly where a direct replacement has a long lead time or is no longer available.
Where repair is not the best option, Completely Hydraulic can also support hydraulic cylinder manufacturing.
See our full guide: Repair or Replace Your Hydraulic Cylinder?
The best repair is one that also considers why the cylinder failed.
If the same component repeatedly fails, investigate factors such as:
Root-Cause Thinking
A repeatedly leaking cylinder, damaged rod or failed seal is often telling you something about the machine. Looking for the root cause can prevent the repaired cylinder returning with the same problem.
Hydraulic ram maintenance works best as part of a broader preventative-maintenance plan.
This can consider:
The maintenance schedule should reflect machine usage, risk and condition rather than relying on one fixed interval for every application.
See Hydraulic Preventative Maintenance.
Large hydraulic rams from excavators, loaders and industrial machinery can be difficult to transport.
Completely Hydraulic offers a free hydraulic cylinder repair collection service for qualifying repair work, subject to location, cylinder dimensions and repair requirements.
See Free Hydraulic Cylinder Repair Collection Service.
Jump the queue. Reduce downtime. Pay less for parts, labour and callouts.
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Completely Hydraulic supports construction, plant, industrial and heavy-equipment operators with:
For wider plant support, visit our Construction Hydraulic Services page.
The Bottom Line
Heavy-equipment hydraulic ram reliability depends on more than seals. Rod condition, mounting alignment, contamination, hoses, hydraulic oil and the machine’s working environment all influence cylinder life. When the same fault returns repeatedly, investigate the cause rather than continually replacing the failed part.
If a ram is leaking, drifting, binding, physically damaged or repeatedly failing, Completely Hydraulic can assess the cylinder and advise on repair, refurbishment or replacement.
A hydraulic ram, commonly referred to as a hydraulic cylinder, converts hydraulic energy into linear force and movement to operate parts of machinery such as booms, buckets, blades and lifting mechanisms.
Common problems include external leakage, rod scoring or corrosion, seal failure, internal leakage, mounting wear, misalignment, binding and physical damage.
Possible causes include rod damage, misalignment, side loading, contamination, excessive heat, damaged gland components or unsuitable sealing components.
Sometimes, but the rod, gland and other cylinder components should be checked first. A damaged sealing surface can quickly cause a new seal to fail again.
Internal cylinder leakage is one possible cause, but control valves, load-holding valves and other circuit faults can also allow movement.
The correct repair depends on the extent and type of damage. Some rods may be repairable or reconditioned, while others may require replacement or manufacture.
There is no universal interval. Inspection should reflect OEM guidance, operating hours, workload, environment, condition, machine criticality and previous failure history.
No. Many leaking cylinders can be repaired or refurbished. Replacement becomes appropriate when condition, repairability, availability, cost, downtime or safety makes it the better option.
Yes. CH supports hydraulic ram and cylinder repair for construction, industrial and heavy equipment, depending on the cylinder and application.
CH offers free hydraulic cylinder repair collection for qualifying work, subject to location, cylinder size and repair requirements.
