What Causes Hydraulics Cylinders to Leak?

Almost all hydraulic cylinders within their working lifetime will show signs of a leak. However, if issues are spotted early enough leaks can be minimised and easily fixed.

Here we look at some of the main causes of leaks in hydraulic cylinders and how to prevent them.

How to spot an internal hydraulic leak in a cylinder.

If you notice a pressure change in your hydraulic cylinder, or the cylinder starts to drop under its own weight, chances are there is internal leakage across the piston seal. Fluid that leaks into other areas of the cylinder, affects the motion of the rod. This causes the movement of rod in the cylinder to slow down, as it disperses the fluid to get back into the open position.

Another tell-tale sign of a leak, is a visual leak and having to replenish the hydraulic fluid in your machine more frequently than usual, causing an increase in your operating costs.

Main causes of a hydraulic cylinder leak

Wear & Tear

A worn or damaged Piston seal or cylinder component can cause fluid leakage. Even the tiniest of cracks can cause hydraulic fluid to enter other parts of the system.

Although the wear is unlikely to be visible without closer inspection, a drop in the machinery’s performance is usually an indicator that there is a problem within the cylinder, and its individual parts should be assessed.


Dirt, debris, or small pieces of metal that break off other parts of the machine and enter the system can damage components within a hydraulic cylinder and cause an internal leak.

Contaminated hydraulic fluid such as water can cause a white milky fluid, which invariably results in corrosion. Some biodegradable oils if not changed regularly at service intervals can break down and cause sludging and components to stick.

Ensuring that your cylinder is kept well lubricated and protected from external contaminants will prevent this problem from occurring. If you suspect your hydraulic fluid is contaminated, you should flush and replace the fluid as quickly as possible.

Poor maintenance

Problems can occur if the individual components of a hydraulic cylinder have been poorly fitted or maintained. For instance, if seals are fitted incorrectly or over-tightened this can cause the seal to crack and lead to the deterioration of other parts over time.

Ensuring the cylinder is properly fitted by a skilled engineer and kept regularly lubricated, will prevent this from happening.

Changes in operating conditions

Exposure to high temperatures, or heat from high-speed or overuse can damage the seals and O-rings within your hydraulic cylinder and cause it to leak.

Therefore, it is vital to take a machine’s operating conditions into account when selecting the right seals and parts for your cylinder. Some applications require seals manufactured in materials that can withstand high temperatures and high pressure.

Replacing hydraulic cylinder seals and parts

FPE Seals provide replacement parts for all hydraulic cylinders and specialise in providing sealing solutions for aftermarket applications.

View what is on offer on our website or contact one of our knowledgeable team today who are happy to advise on finding you the best part for the job.



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