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Hydraulic Repair

Trouble Shooting












Typically, 90 to 95 percent of pump failures can be attributed to one or more of the following causes:

  • Aeration
  • Cavitation
  • Contamination
  • Excessive Heat
  • Over-Pressurization

Each of these conditions leaves its own distinctive type of damage marks. It's important to recognize & understand those telltale signs. That way, the real cause of pump failure can be corrected.

Use this guide to determine the type of damage that has been done to your pump so the cause may be corrected. Use this information to prevent future pump failures. Detailed Photos indicate the type of damage that has been caused.


Contamination - Any Material foreign to hydraulic fluid that has a harmful effect on its performance in its system.

Types of contaminants: Solid Liquid or Gas.

Metallic Oxide: Improperly cleaned welding burrs breaking off in the system

Absence Of Filters: Dust particles enter the system

Aeration: The presence of dispersed bubbles of air in a system's hydraulic fluid. An implosion effect occurs when the compressed air bubbles are subjected to system pressure at the pump outlet.This implosion can cause metal to be removed from the pressure plates, etc. near the implosion point and result in extremely high local temperatures.

Pump Aeration: A loud, crackling noise like marbles being pumped. The noise is higher pitched at higher pressures. Excessive aeration makes the fluid look milky. It also causes components to operate erratically because of the compressibility of the air trapped in the fluid. Possible ways that air could be sucked into a pump are through faulty shaft seals and leaky inlet joints

Cavitation: When the fluid doesn't entirely fill the existing space. The noise from cavitation is similar to that heard from aeration. Cavitation can be caused by over speeding of the pump, including a restricted or excessively long intake line, or fluid viscosity that is too high.

Contamination: Any material foreign to a hydraulic fluid that has a harmful effect on its performance in a system. Contaminants can be solid particles, liquid or gasses. Most contaminants cause an abrasive action in the close mating tolerances between components. This results in accelerated wear and tear.

Excessive Heat: Thermal condition above specified limit causing fluid viscosity to be affected. An extreme system duty cycle, aeration, cavitation, over-pressurization, and contamination are all factors that contribute to excessive heat in turn, accelerates oxidation in the system fluid, deteriorating its viscosity. This creates a chain reaction. Therefore, the root cause of excessive heat must be eliminated in order to effectively cure the problem.

Implosion: A sudden, violent, Inward collapse. Implosion of air bubbles when subjected to hydraulic system pressure. This can cause severe pump damage.

Over-Pressurization: Subjecting a pump to operating pressures grater than those for which it was designed. Over-pressurization creates extreme forces against various internal components and can result in premature failure.

Viscosity: A measure of a fluid's internal friction resistance to flow. Higher than recommended viscosity (as might be the case with very cold oil) may cause pump cavitation. Lower than recommended viscosity can cause increased internal pump leakage and an accompanying increase in heat . Therefore fluid of the recommended viscosity level, to which the manufacturer has added appropriate additives, is one key to longer pump life.





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All manufacturer's names, numbers, & descriptions are used for reference purposes only.
It is not to be implied that any item is the product of these manufacturer's.