Recently running my 304.5 mini excavator and within a 2 hour span my hydraulic oil changed from a transparent honey color to a dark grey/ black color. I recently purchased, so it may just be that it took that long for any newly added oil to mix with whatever old oil was already in the system but I have not been able to find anyone with any ideas as to what steps I should take next. Upon opening the hydraulic tank I did not witness any cream from water intrusion or bubbles. So at this time I sent the oil out to have an analysis done and am waiting to hear back. Below are the two pictures of my hydraulic oil sight gauge of the before and after it had changed color. Any insight is greatly appreciated. Before: https://ibb.co/gFp6xcb After: https://ibb.co/k4VFYqJ
You will have a better idea of what needs to happen when you get the analysis report. Color of oil is not a good test.
Any new cylinders on the machine? Are the pumps quiet?
Any hydraulic overheating history ? Do you have a hydraulic oil cooler ? Some machines have integrated engine oil cooler or intercooler and hydraulic cooler so if such is the arrangement you must monitor your engine oil level ,also a fucked up turbocharger too
Your oil level rose too. Engine oil mixing in somehow?
I have had my oil go black about a month ago when I blew a hose and they refilled the machine with a oil that had a blue dye in it (Pirtek) and the oil in the machine was a honey color (Valvoline) the oil went that black you could not see the silver backing of the site glass in bright sunlight, The company assured me it was new oil and may be a reaction in the dyes, all seems to be good on the machine (Bobcat 435) I am not sure?