just as an experiment, I took some brand new red 5606 hydraulic fluid and put it on a dirty old paint can lid. Next morning it wasn't red. (I don't know why: because it spread out, dye evaporates, fluid evaporates or what.) Looked a lot like your picture.
Drying hydraulic fluid evaporates and thickens. More copious old hydraulic fluid very thick approaching gummy.
Your picture also looks a lot like what it looked like around my leaking emergency hand pump. I looked for a hydraulic leak and not an oil leak because that was what was most likely for the circumstances. I found a hydraulic leak and it stopped the problem.
5606 Hydraulic fluid is in the brakes as well as landing gear system.
Last edited by wslade2 : 03-15-20 at 07:16 PM.
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