Construction and other equipment - Filtering hydraulic oil

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Filtering hydraulic oil

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Construction and other equipment
Forum Description: everything else with orange (or yellow) paint
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=57639
Printed Date: 25 Jun 2025 at 8:25am
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Topic: Filtering hydraulic oil

Posted By: Dozer
Subject: Filtering hydraulic oil
Date Posted: 30 Sep 2012 at 11:41am

My latest HD6G blew the pressure line at the pump. I replaced the hose and filled up the oil tank. After cycling the hydraulic system the oil was dirty so I changed it again. Then I drained the hydraulic oil to change the steering clutches it was dirty again. I know that hydraulic machine tools filter and reuse their hydraulic fluid. I set up an electric hydraulic pump with a large aftermarket diesel fuel filter and ran the oil thru it. The oil still looks muddy.

My question

Is there a filter available that would allow me to reclaim this oil. I thought that a fuel filter would take out more particals than an engine oil filter. Am I correct?

Replies:

Posted By: DMiller
Date Posted: 30 Sep 2012 at 2:43pm

We filter our hydraulic oil in the plant I work in, mainly to remove the material that enters through the cycle of vent air into the systems. Your tractor should have a filter system on the hydraulic tank to do that, my HD7G is set up that way yet it will still draw some dirt and the moisture that enters in the vent air will cause some internal corrosion which will discolor the oil some, cltches will deliver some particulates as the oil cycles through them. Biggest issue is the break down of the oil corrosion inhibitors and friction additives, you can somewhat replace them but not fully and that is why we change the fluids.

Posted By: Dozer
Date Posted: 30 Sep 2012 at 4:37pm

There are filters in the hydraulic tank. When I drained the tank I probably replaced about half the oil in the system. I have about 30 gallons of oil that was only in the machine a few minutes. I was trying to reuse it because I am miserly.

Posted By: DMiller
Date Posted: 30 Sep 2012 at 4:52pm

May have some 'color' to the new old oil, slight filtering may not remove the really small(<40 micron) particles but it should be safe to reuse. Does not have to be clear to be usable and functional. I have also left drained 'new' oil sit for a few days, as the suspended solids settled I would pour off the 'clean' oil to a clean container and then discard the sludge.

Posted By: Coke-in-MN
Date Posted: 30 Sep 2012 at 8:05pm

I set up some filters using filter cans for AMF Cuno filters , 2 filters in-line the first being a 30 micron and the 2nd being a 10 micron, then circulated the oil on a continuous cycle for a couple days , as the filters slowly filter out they become more efficient and the oil got cleaned well . The 30 micron did plug up and changed it and let it circulate another 2 days , looked almost new when done.

Friend use to get me the used ATF from the machine shop he worked at , would get 3 55 gal drums and leave them filter for a week or two after they had set for a month or so to settle anything out. I just transferred the first 50 gallons and took the lower 5 gallons and disposed of it.

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Posted By: orangeman
Date Posted: 30 Sep 2012 at 8:06pm

How about using a small centrifuge to separate the water from oil? I have not researched this much so uncertain if it would be sufficient enough to remove enough water, particularly those fractions that are soluble.