Autopilot hydraulic oil contamination

[Northbound44]

Did anyone experiencing hydraulic oil contamination in autopilot system?
The bypass solenoid valve in my unit was clogged with the same kind of fungus or bacteria we could find in diesel fuel in the tropics. Since the complete system appears to be contaminated, I would like to purge and replace the oil and I want to know if adding biocides like the one we use for diesel could be a preventive measures. I want to know if this could be harmful for the system.


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[exMaggieDrum]

We never had a problem in ours and I don't remember anyone else that I ran in to ever mentioning it. That's not to say it may be a broader problem. I doubt that the hydraulic manufacturers of your system would recommend adding anything to the fluid. You certainly need to thoroughly purge the system. I'd contact the hydraulic company(ies) and ask them for what they would recommend. Or there may be a lot of info on line. And then put in the fluid they recommend. I used ATF instead of the "recommended" stuff but if I get a new one (soon) I will use the vendor-specified stuff, at least until the warranty is over. They are pretty fussy about that.

[Lepke]

Micro organisms need water to survive. Their growth in a system means water is getting into the system either thru leaks or condensation. Without biocides, changing the oil will not solve the problem. Hydraulic biocides are available from professional hydraulic supply companies.
Some diesel biocides contain ethanol that may hurt seals and o-rings. A filter might help, but most small boat hydraulic steering doesn't really circulate. It just goes back and forth in the lines enough to move the cylinder.

[exMaggieDrum]

Thanks Lepke. You seem to be on top of this subject. I found this:

Stopping Bacteria Growth in Hydraulic Oil - techenomics.net

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