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what solvent is best for flushing hydraulic system


Ultra Member
I had forgotten about filter carts that could be rented, maybe because of a boss that would not get more filters to do the job right and going on about the cost when we used it. Maybe 40 years got something to do with it too. LOL.
Not sure I would brother with the old oil as it may not be the right stuff anyway and plug filter on cart fast. If do use old oil, run filter cart first for a while to clean up oil in sump before running grinder hydraulic pump.
Sounds like you got a plan!!


Super User
For what it's worth a Shell rep told me once its a good idea if you can, to filter new oil right from the drum as there is usually a small amount contaminants. I've only done it once while replacing oil in a large turbine . Not sure if it really helped , as the gauge on the filter cart never really moved.


Well-Known Member
As others have said, flush it with hydraulic oil. On my TOS SG, the hyd oil sump was horrible. I added a bypass filter off where the pressure gauge goes (just a spin on from PA). A 1/16“ orfice worked out great (remember the oil pressure is pretty low). I added the filter after the first flush. The entire base of the machine is the oil reservoir (no nice little tank). I started by cleaning the sump thoroughly - sucked the oil and crud out, then washed and wiped it clean. The suction strainer was so obstructed , I don’t know how any oil got through. On the first flush I used a mixed blend of whatever I had left in 3 miscellaneous hyd oil pails. The oil was milky in about 10 seconds of operation. I sucked the sump out again, wiped it out and washed it with kerosene, left it to dry. Then I filled with the recommended oil ISO22, this time with the new filter in play. Let it run about 15 minutes, still milky. Sucked the oil out again, cleaned the reservoir and replaced the filter. Refilled with ISO22.

I’ve now run the machine about 15 hours, the filter gauge hasn’t moved (ie the filter dp is unchanged).

I don’t like how this machine has the hyd system set up, any coolant spray or overflow from the grinding table will end up in the oil sump. There is a rinky dink shield that had failed, I fixed it and added additional shielding - still not great IMO. It runs well and grinds nicely, so hopefully all is good.