Water Contamination in Oil
This is water mixing into the hydraulic oil. When the oil takes on more water than it can dissolve, it takes on a milky, cloudy appearance. Water leads to corrosion, breakdown of the additive package, and a loss of load-carrying capacity in the oil film; on proportional valves it shows up as sticking and sluggishness.
Water enters the system by three routes: humid air drawn in through the tank breather condensing as it cools, covers and seals that leak during pressure washing, and internal leakage in the oil cooler.
- Visual sign: the oil turning milky. By the time the cloudiness is visible to the eye, contamination has already advanced.
- Other signs: water droplets under the tank cap on cold mornings, rust-colored sediment, unusual foaming.
- Because water weakens the oil's lubricating film, wear accelerates on pump and valve surfaces; in the cold it can freeze and block narrow passages.
Prevention is far cheaper than treatment: use a moisture-absorbing breather filter, fill the tank so little air space remains, and do not aim a pressure washer jet directly at the area around the cap. Contaminated oil is generally replaced; dewatering units can be used for small amounts, but any measure taken without finding the source is temporary.
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