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Mechanics Corner: Preserving your machine’s hydraulic system

Jeff Brown for Progressive Dairyman Published on 05 August 2016

It’s no secret that a healthy machine translates to increased uptime and efficiency on your farm. Therefore, implementing a strong maintenance strategy and preserving the machine’s hydraulic system are critical. However, it’s easy to overlook the hydraulic system when completing machine walk-arounds, as it’s not always visible from checkpoint areas.

That doesn’t mean it’s any less important. A machine’s hydraulic system determines how much material you move and how fast you move it.



One of the most important items to check on a daily basis before operating your machine is the hydraulic oil level. Operating on a low level generates more heat in the hydraulic oil and can cause faster breakdown of the fluid and machine components.

Think of the hydraulic oil as the lifeblood of the machine and the pump as the heart. Heat causes thermal breakdown of the hydraulic oil, ultimately causing it to lose lubrication. This broken-down oil will then circulate through the machine pump and other components, causing wear on the parts. Which brings us to a key point: Heat is the silent killer of a machine’s hydraulic system.

Increased system heat (above 190ºF) is an early warning sign of a hydraulic system issue. Thermal breakdown of the oil starts to occur when temperatures begin to rise above this point. Another early warning sign of an issue is machine performance loss or atypical machine movement, such as cylinder drift. If you notice any of these symptoms, it’s time to contact your dealer.

Fortunately, today’s advanced machines have been engineered with features specifically designed to keep the hydraulic fluid cool during operation to avoid breakdown of the pump and other important components. If you are spec-ing a new machine, ask your dealer the following questions:

  • How large is the hydraulic fluid tank? Larger tanks allow the fluid to cool faster before circulating through the system.

  • How large is the hydraulic cooling pack? Similar to the hydraulic fluid tank, the larger the cooling pack, the more effective it is in cooling the oil.

  • How are the engine cooling pack and hydraulic cooling pack positioned within the machine? If the cooling packs are stacked on top of one another, they allow airborne debris to get trapped in between the components.

    This positioning makes them harder to clean out, thus creating inconsistent airflow through the cooling system. Machines with cooling packs positioned side by side are ideal to maintain consistent airflow for the maximum cooling effect.

  • Is the fan speed controlled by the engine or the hydraulic system? An engine-driven fan is a constant parasitic load on the engine and may not spin fast enough to cool the oil.

    A hydraulic-driven fan is temperature sensitive, meaning that it measures hydraulic and coolant temps, and only spins as fast as it needs to in order to cool the oil. That way it doesn’t become an unnecessary load on the engine when it is not needed, which saves fuel.

  • Can the fan’s airflow direction be reversed? Reversing fans allows you to redirect the airflow to blow away any debris that has accumulated on the grill throughout the day.

Another common issue that occurs in machine hydraulic systems is cavitation. Cavitation happens when high pressure generated by the machine pumps causes voids, or holes, to form in the hydraulic oil. If these voids are drawn back through the pump, as soon as pressure is applied, it causes them to explode.


These void explosions cause erosion of the metal parts of the pump. Unfortunately, it is impossible to detect cavitation with the naked eye, so it is hard to catch the erosion in an early stage in order to prevent further issues, such as pump efficiency loss. On a positive note, many advanced machines are equipped with anti-cavitation hydraulic oil tanks.

These tanks force the voids in the oil to disperse in order to avoid being circulated back through to the pump, ultimately preventing pump and component erosion.

An additional component of the hydraulic system to consider is the hydraulic oil itself. It is important to pay attention to the manufacturer’s recommended oil change intervals.

With many manufacturers recommending hydraulic oil changes every 1,000 hours, machines that employ extended-life hydraulic oil can help reduce your overall maintenance costs. Today’s advanced hydraulic systems utilize hydraulic oil that can last up to 6,000 hours.

Last, but certainly not least, let’s talk about hydraulic oil leaks. Leaks can quickly cause reduced oil levels and degraded machine performance. It is important to periodically check for leaks throughout your machine.

However, this can be a time-consuming task, as many hydraulic system lines and components are often located underneath the cab, especially on compact machines. In this case, you must raise the cab in order to properly inspect for leaks.


If you are spec-ing a new machine, the component layout underneath the cab is certainly something to consider. Look for features that will make inspections and repairs easier, such as:

  • Organized, open-space component layout and contrasting part color – This will make it much easier to spot leaks or any other issues.

  • Labeled hoses and components – If the hydraulic hoses and components are labeled with part numbers, you can easily call your dealer to order it for pick up or delivery if a leak or issue is detected.

    If the hoses and components do not have labels, they typically have to be brought into the dealership to make sure the replacement part is properly matched, translating to a longer period of machine downtime.

Preserving your hydraulic system and acting on early warning signs can help you avoid costly repairs and reduce downtime.  PD

Jeff Brown
  • Jeff Brown

  • Compact Equipment - Product Specialist
  • Caterpillar Inc.
  • Email Jeff Brown