The Number One Cause Of Water Contamination In Pressure Washer Pump Oil: Cracked Pistons
The most common cause of water contamination in the oil of a pressure washer pump is cracked or fractured pistons. Pistons are the core component that helps generate pressure in the pump, and when they crack or break, they become a channel through which water is pushed into the pump as the pistons continue to move.
The pistons are, without fail, the first thing we check when investigating why there is water in the pump oil.
What Causes Pistons To Fracture And Crack?
The main reason pistons crack is due to stress caused by the pump freezing. If the pressure washer is exposed to freezing temperatures and the pump has not been winterized, then the water can freeze and expand, which puts significant pressure on the pistons, causing them to fracture and crack. Excessive heat can also ocassionally cause stress fractures on the pistons.
Identifying A Cracked Or Fractured Pressure Washer Piston:
Small fractures can be hard to see, expecially if the pistons are ceramic. If you see any fine lines or cracks, the piston needs to be replaced immediately. Even if the fracture looks harmless, it will turn into a crack, which could shatter inside the pump.
If you have pistons with fine lines and fractures, and you flush out the crankcase/change the oil without replacing them, you will run into the same problem again with contaminated oil. It is not a matter of "if" but "when" they will break.
"Fractured" Piston
"Cracked" Piston
What To Do About Cracked Pressure Washer Pistons
If you discover that your pistons have fractures or cracks, they must be replaced. Once you have repaired the cause of the oil contamination, you'll need to clean out the crankcase. We have a blog post on how to properly clean a pump that has contaminated oil here: https://www.allpartsinc.com/blog/changing-pressure-washer-oil-that-has-water-in-it.html