Why Is There Water In My Pressure Washer Pump Oil?

Water inside the crankcase of a pressure washer pump
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Why Is There Water In My Pressure Washer Pump Oil?

Discovering water in your pressure washer pump oil and figuring out how it got there can be a frustrating process. It can be caused by any number of reasons, and you have to figure out the problem and fix it, because if you just clean out the crankcase and go right back to using it, then water will find its way back into the oil. This post will walk you through the process of diagnosing one very specific reason why water is in your pump oil: a stuck bypass valve.

Diagnosing A Stuck Bypass Valve

  1. Symptom: water has contaminated your pressure washer pump oil
  2. First thing to check: Ceramic pistons
    • The ceramic pistons in the crankcase are always the first part that we check when repairing a pressure washer pump that has oil in it.
  3. Second thing to check: The manifold
    • When we inspected the manifold, we found crushed spacers. This immediately lets us know that the bypass valve is the problem

Diagnosis: The check valve was stuck in the bybass valve and a spring inside the check valve was broken

Because the shutter bypass valve was stuck, the pressure washer could not go into bypass mode. This caused the pump to over-pressurize, push the water seals against the spacers, and crush the spacers. After this, water can escape from the brass manifold and be drawn back into the crankcase by the pistons' in-and-out movement.



Fixing The Pump:

Replace the bypass valve and the crushed spacers. Make sure to check your instruction manual to ensure that you are ordering compatible parts for your specific pump. Then thoroughly clean out the crankcase (we have instructions for this here). After this is done, your pump should be ready to reinstall and test on your pressure washer.


Do you need help troubleshooting your pressure washer problems? Leave a comment below, or you can talk to a technician today by contacting us.

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