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Hydraulic maintenance 101

How to properly maintain the hydraulic system on a mid-size crawler excavator

Hydraulic maintenance performed on a Doosan excavator
With regular maintenance, a crawler excavator's hydraulic system should perform well season after season.

At the heart of a crawler excavator is its hydraulic system. Without a properly maintained hydraulic system, it's impossible for an excavator to work efficiently.

With regular maintenance, a crawler excavator's hydraulic system should perform well season after season. Without consistent care, there is potential for real risk for both the machine and the operator. 

Hydraulics 101

Originally called the hydraulic excavator, a crawler excavator is controlled, unsurprisingly, hydraulically. An excavator's hydraulic system allows small forces to be converted into big forces.

"Nearly every part of an excavator is tied to its hydraulic system," says Aaron Kleingartner, product and dealer marketing manager, Doosan Infracore North America. "For example, the excavator's diesel engine is connected to the hydraulic pump. The pump supplies the flow and pressure to the various functions of the machine. As the pump spins, oil travels through the system, allowing the excavator's tracks, boom, arm and bucket to operate." 

The excavator's front workgroup can be precisely controlled with fine movements of the joystick controls. The hydraulic travel motors are what makes a machine move from point A to point B on a job site. Most machines have 2-speed travel motors; high range for travelling and low range for better power when working. When an excavator needs to turn while travelling, some machines will auto downshift into a low range to more effectively manage the turn.

How important is fluid?

Hydraulic systems run on fluid. The correct fluid, specifically oil, should flow through an excavator seamlessly. There are additives within the hydraulic oil that can help keep the components, or the entire system, clean. Additives ensure that any water or condensation that makes its way into the tank is separated properly. Water separators can assist with that process; however, they need to be drained regularly to keep the systems running optimally.

"Quality hydraulic oil is necessary to ensure the crawler excavator is working properly," Kleingartner says. But what if the wrong or contaminated fluid makes its way into the machine's hydraulic system? "The machine simply won't run properly," he says. "If you suspect that the incorrect fluid has entered the hydraulic system, it's best practice to speak to your service technician or dealer as soon as possible to avoid further damage to the system." 

It's also highly recommended to keep track of how often the excavator's hydraulic oil is changed. For a standard, mid-size crawler excavator, the oil should be changed every 2,000 operating hours. Additionally, for every eight to 10 hours of work time, it's suggested that an operator checks the hydraulic oil level to ensure everything is working properly. Owners and operators should follow the prescribed maintenance schedule in the machine's Operation and Maintenance Manual. Every new machine should come with this manual. If you don't have a copy, contact your dealer to order a replacement or get access to an electronic version.

"If the excavator's hydraulic oil is never changed, it will age and can cause buildup of contaminants in the machine's hydraulic system," Kleingartner says. "The old oil can damage other components of the hydraulic system, leading to a reduction of the machine's overall efficiency." 

Daily maintenance 

As you or your excavator operators prepare for work, they should perform a machine walkaround. They should check the machine's overall condition. Particularly, they should look for any leaks or damaged hydraulic pipes or hoses. Making sure that nothing looks suspicious before operation may prevent a headache later on if something goes wrong. 

"When examining the machine's hydraulic pipes and hoses, you or your operator should specifically note if they're well-secured to the excavator," Kleingartner says. "If not, the mounting hardware should be fixed immediately. A damaged hydraulic hose could vibrate excessively and may leak oil. Any sign of wear on pipes and hoses should be addressed as soon as possible."

Work with your local dealer to make sure the hydraulic pipes and hoses are installed and maintained properly to avoid unplanned machine downtime. If there is a hydraulic oil leak, be sure to address it and avoid contamination.

At the heart of a crawler excavator is its hydraulic system. Without a properly maintained hydraulic system, it's impossible for an excavator to work efficiently.

Prepare for storage

When it comes to long-term maintenance, properly preparing a machine to be stored during winter is a crucial step. If you need a refresher on storage procedures for your excavator, refer to your Operation and Maintenance Manual. 

"Before storing your machine during winter, ensure that all fluids are topped off and any water is drained from the hydraulic system," Kleingartner says. "If the water isn't drained from the system, this can potentially lead to a frozen or busted pipe. Additionally, if there is a slow hydraulic leak that sits for multiple months, it can lead to a negative environmental impact. All of this can be avoided by doing one last walkaround before storage. You may want to periodically check your machines during winter if they sit for an extended time."

As the snow melts and the ground thaws, you should prepare your machine to get back up and running.  Check that there weren't any leaks during winter storage. If there are any, be sure to repair them before operating the machine


In warmer months, you or your operator needs less time to get your excavator up and running. However, during colder months, it's important to follow the machine's hydraulic system warm-up process. The excavator's hydraulic system runs more efficiently when the hydraulic oil flows smoothly, especially in the colder months. In cold weather, the hydraulic oil may become thicker than normal. To combat that, many manufacturers offer a hydraulic system warm-up procedure.

The warm-up procedure allows the hydraulic system to reach an ideal operating temperature. The pressure of the hydraulic system helps to increase the temperature, allowing the oil to flow through the machine more easily. This gradual warm-up is less harmful to other machine components than if you or your operator immediately tries to operate a machine in colder weather. 

Protecting hydraulic components

Some parts of the excavator's hydraulic system require little to no maintenance. For example, the hydraulic pump only needs to be checked periodically to ensure it's mounted securely and working properly. Since it's in the centre of the machine, it's well protected by the other components. There are many other components, however, that need to be monitored. 

Hydraulic system components to examine more closely include the following:

  • The oil cooling system, a vital component of the hydraulic system, is located near the exterior of the excavator. This allows the cooling system to draw in cool air. 
  • Machine panels, which typically cover vital components. It's important to keep these panels clean and free of loose debris. Make sure the panels close and latch properly.
  • Cylinder guards, which can be both standard and optional components. Depending on your line of work, you may or may not need the guards. Inspect the guards to make sure they are properly mounted for operation.

Personal protection equipment

The best way to prevent an injury when working on or around an excavator's hydraulic system is to carefully follow the maintenance procedures. When working on a hydraulic system, you or your operator should wear the correct personal protection equipment (PPE). It's highly recommended to protect your eyes and skin. 

Pressurized hydraulic oil can break the skin easily and make its way into your body. To prevent this injury, wear the proper PPE as identified in the Operation & Maintenance Manual when working on the hydraulic system. Additionally, be sure to wear well-fitting eye protection in case any liquid splashes or sprays. Immediately seek medical attention if any liquid makes contact with your eyes or breaks the skin. 

By following these recommendations, you can help make sure your crawler excavator's hydraulic system is working properly and help to minimize any machine downtime.

Rachel Ori works in Strategic Communications based in Des Moines, Iowa.

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