Why Does Hydraulic Oil Get Hot – Common Cause & Solutions

Is your hydraulic oil getting too hot during regular use? Running pumps naturally generate heat, but designers have set specific heat limits for them. Overheating is not normal. It can cause problems such as thinning hydraulic fluid, reduced lubrication, increased wear on parts, and pump failure.

Ignoring a pump that exceeds its heat limits under normal load isn’t advisable. Several factors can cause excess heat buildup, which we’ll explain in this article.

In heavy machinery, the hydraulic system handles the heavy lifting. It’s crucial for many business tasks. Proper care is vital to avoid component damage, maintain efficiency, and keep workers safe. 

Hydraulic systems are crucial for heavy machinery, but they can overheat. Understanding why they overheat helps maintain efficiency, prevent downtime, and extend equipment life.

Importance of Hydraulic Oil in Maintaining System Performance

Hydraulic oil is crucial for various industries. It helps machines run smoothly by transmitting power and reducing friction. From construction to aerospace, it’s essential. 

Hydraulic oil is made to move power in hydraulic systems. It’s a mix of base oils and additives, chosen based on system needs like temperature and pressure.

Hydraulic oil is important for keeping machinery running smoothly across industries. It helps transmit power, reduces friction, and handles temperature changes. From construction to aerospace, agriculture to manufacturing, it boosts productivity and safety. 

As technology advances, specialized oils are being tailored to meet specific industry needs. This promises better efficiency and performance for the machinery driving our modern world.

Why Hydraulic Oil Gets Hot

When hydraulic oil overheats, several common causes can lead to system overheating. To troubleshoot the issue effectively, it’s essential first to understand the type of hydraulic system you’re using.

Regular system maintenance is crucial for identifying potential overheating issues before they escalate. It ensures that hydraulic fluid, parts, and components are all functioning optimally.

The System Parts and Components are Wearing Out and Require Replacement

One reason hydraulic oil overheats is when system parts near the end of their useful lifespans. As they wear out, internal leakage increases, making them work harder to maintain pressure.

If your hydraulic pump is wearing out and needs to be replaced, internal wear is causing fluid to leak. The fluid is leaking from the high-pressure side to the low-pressure side. This generates heat, raising the oil temperature and causing overheating in the circuit.

Contaminated Hydraulic Fluid

The system must work harder when dirt, sludge, debris, or water is present in the hydraulic fluid. This extra work generates more heat as the fluid is moved. So, it’s important to regularly check for contamination and replace the fluid or improve filtration when needed.

The System Pressure Unexpectedly Rises

In a hydraulic system, each component applies pressure to the pump, known as the pressure drop. This pressure drop varies with the flow rate. The fluid loses energy due to this pressure drop, converting it into heat. If the pressure drop in the circuit goes up, the heat generated in the circuit will also increase.

Without cooling to offset this, the fluid temperature keeps rising as other parts and components generate excessive heat.

Effects of High Oil Temperature

Extremely high temperatures can have several harmful effects on hydraulic systems, including:

Increased Oxidation

High temperatures cause hydraulic fluid to oxidize faster, creating sludge and varnish. These byproducts can block lines and valves, decreasing efficiency and performance, and may even cause a system failure. For every 10-degree rise in temperature, the oxidation rate doubles.

Loss of Lubrication

High temperatures reduce the oil viscosity in hydraulic cylinders, making them less effective at protecting moving parts. When the oil gets too hot, it increases mechanical wear, leading to more frequent pump and cylinder replacements.

Seal Failure

Hydraulic seals work best between 110 to 130°F. If they get too hot, their properties can change, causing them to fail. This leads to oil leaks, system contamination, and metal-to-metal contact, which can damage cylinder parts.

Importance of Monitoring Oil Temperature

Hydraulic oil temperature is the range of temperatures it faces in a hydraulic system. It can vary a lot based on different factors, which can make it dangerous if you’re not experienced in handling it.

The outside temperature matters: hotter climates mean hotter oil, while colder ones mean cooler oil. And, how much work the system is doing and how much pressure it’s under also affect how hot the oil gets. More work and pressure mean more friction, which makes the oil hotter.

Another thing to consider is how fast the hydraulic fluid moves through the system. Faster flow rates can make the oil hotter due to more friction and heat. Slower flow rates might mean less heat generated.

The design of the system also matters. Good cooling systems like heat exchangers or cooling fans keep the oil at the right temperature. If the cooling is not enough or the design is poor, the oil can overheat. This can lower efficiency and damage the system’s parts.

Checking the oil temperature in hydraulic systems is crucial for smooth operation and longer lifespan. Too much heat can break down the oil, make lubrication less effective, and speed up wear on parts.

So, using temperature monitors and doing regular maintenance is important to prevent overheating and keep hydraulic systems working well.

Tools and Methods for Measuring Oil Temperature

You can measure hydraulic fluid temperature using simple tools like thermometers. Advanced devices are also available that send signals to the control unit in hydraulic systems.

The CFP Cubic sensor can check the oil level and temperature in a hydraulic press tank simultaneously. It can do this regardless of the material it uses. It detects even the smallest levels with minimal dead zones. You can also use the LFP Cubic TDR level sensor with the TBT temperature sensor.

For the highest quality components, use either the PBS Plus digital pressure switch or an analog PBT pressure transmitter. These devices measure the pressure in the system and during forming processes.

Having these important hydraulic tools will reduce downtime and save money by checking for failures before replacing components.

Infrared Cameras 

Heat is a major issue in hydraulic systems, but finding its source can be tough. Most systems run between 100-120°F. Infrared cameras are the go-to tool for pinpointing heat sources and are invaluable for troubleshooting hydraulic problems.

Portable Pressure Testing Kit

The pressure gauge is vital for troubleshooting hydraulic issues. Gauges permanently installed on equipment can become damaged over time, which can make them hard to read.

A portable pressure testing kit ensures accurate readings. It is designed to work with the common quick disconnect ports that modern equipment has. If your equipment does not have these ports, you can add them to ensure compatibility.

Voltage Detector

An often overlooked tool for maintenance technicians is the voltage detector. Using it simplifies the process of checking if a solenoid is energized, making it quick and easy. When troubleshooting, start by using the voltage detector to rule out valves that aren’t causing the problem. Then, focus on identifying valves that could be the issue.

Preventing Hydraulic Oil from Getting Too Hot

Overheating is the second most common issue in hydraulic systems, after leaks. It occurs when the system isn’t efficient, leading to power loss converted into heat. To keep the fluid temperature stable, the system needs to remove heat more effectively than it generates. 

We can prevent overheating by reducing the heat load on the hydraulic oil or improving heat dissipation. If your hydraulic oil exceeds 82°C, it can damage your system and degrade the oil faster. Preventing overheating is vital. It’s a common issue in hydraulic systems, so keeping the oil cool is key to avoiding costly repairs and downtime.

Typically, you can detect high temperatures when the oil thins beyond the optimal level for hydraulic components. Even temperatures below 82°C can affect viscosity, depending on the oil’s viscosity index. To keep the oil temperature stable, the hydraulic system needs to dissipate heat faster than it builds up.

To prevent your system from overheating, focus on two key steps: lowering the hydraulic oil temperature and improving heat dissipation.

Heat dissipation mainly happens in the hydraulic reservoir. Check its fluid level and ensure it’s right. If it’s low, top it up to the recommended level. Also, check for any obstructions, like dirt or debris, that might block airflow into the reservoir.


If the pressure in a hydraulic system decreases, it can lead to excess heat generation. Likewise, overheating can result from any component leaks. Regularly inspect for leaks and promptly repair them.

Heat Exchangers 

For heat exchangers to work well, they need the right flow rate and temperature of both the hydraulic oil and coolant. Keep an eye out for any dirt or debris buildup, and make sure nothing is blocking the core.

If there are problems with the cooling circuit, you might have to replace parts. Checking the heat exchanger and oil flow with infrared thermometers is a smart idea for efficiency.

Bottom Line

In conclusion, controlling hydraulic oil temperature is crucial for smooth system operation. Excess heat leads to fluid degradation and system failure. Regular maintenance and monitoring, along with tools like infrared cameras, help prevent issues. Emphasizing temperature management maximizes performance and safety, minimizing downtime.


Q1: Can using a different type of hydraulic oil help prevent overheating?

Yes, using a better heat-resistant hydraulic oil can sometimes prevent overheating.

Q2: Can any additives reduce hydraulic oil temperature?

Yes, some additives can help lower the temperature of hydraulic oil. These additives make the oil better at conducting heat or releasing heat. These additives can improve the oil’s performance under high-temperature conditions and help prevent overheating in hydraulic systems.

Q3: How do I know if my hydraulic system is at risk of overheating?

Ans: System issues like noise, high temperatures, and erratic operation are signs of trouble. Contamination, clogged filters, high fluid temperature, or using the wrong fluids often cause poor hydraulic performance.

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