Best way to flush hydraulic fluid

Jaypat88 · Feb 28, 2017

Currently I have about 2 inches of hydraulic fluid sitting in my Hydraulic pump housing after removing the drain plug. I purchased a new lift pump filter and a larger hydraulic filter on the side of my MF40 that runs lines to my front end loader. I am wanting to flush the hydraulic system before send it to the shop to have the lift cover adjusted and installed correctly. What is the best way to flush the hydraulic system and when to install the new filters?

Thank you

BarnyardEngineering · Mar 2, 2017

Normally you just drain what you can, replace the filter, and fill with new. The old oil will dissipate into the new oil and neither you nor the tractor will know the difference.

The problem with "flushing" is that you either drain everything dry, which means the pump has to run dry until it picks up prime, or you have to pump something that is not oil through the system (then how do you get *THAT* out?), which also puts the pump at risk.

ptfarmer · Mar 2, 2017

Jaypat88's setup has the front mount pump, should use the loader frame a reservoir. I wouldn't worry about getting that last little bit out. The hydraulic filter should be on the suction side of the pump so anything that maybe down there would have to make it past the filter. Plus there still is some old hydraulic fluid in the hoses, and cylinders.[/u]

Jaypat88 · Mar 2, 2017

The old hydraulic fluid was coffee brown which makes me think it has water in the fluid. That is why I am wanting to get all the fluid out. Should I fill the reservoir up with new fluid on
top of old fluid and continue to drain until fluid looks clean? Seems like I would be wasting new hydraulic fluid and costly.

Thanks

ptfarmer · Mar 2, 2017

Keep an eye on the fluid, if it changes color after a while change it again (6 months) sooner if gets bad quick. Because the cylinders, and hoses still have fluid in them it may take a few changes. If the fluid you put in stays decent looking change it this time next year.

ptfarmer · Mar 2, 2017

You can put some in, and flush it out the drain. You still won't get all of it out. You can also unhook the hoses, and drain them a long with the hydraulic cylinders by un-hooking the rod end of each cylinder, and move the rod in and out then hook it all back up. Depending on how far you want to get into it.

JBKINWA · Mar 5, 2017

I had some contamination issues with my MF40 Hyd. and steering systems. Wrong fluid (steering) or water in hyd system. It will look more like butterscotch if it is water. Dark fluid that doesn't smell burnt may just be another hydraulic oil type. some are very dark. Best way is change filter and as much fluid as you can in the tank. Once you refill tank, disconnect the return hose for that function of the cylinder (s) you want to flush back at the control valve. Cap the fitting on the valve. I added a union and another length of hose going into a waste barrel and then operated that function pushing the old oil into the waste barrel. Shutting the machine off I then switched the hose and cap to the return line for the opposite function. Topped off the tank and repeated with the opposite function. You just repeat the process as many time it takes until you are satisfied. You can break it all down and do the cylinders and lines by hand but that takes a lot more time and you will have more issues with air in the system.

Best way to flush hydraulic fluid

Jaypat88

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BarnyardEngineering

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ptfarmer

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Jaypat88

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ptfarmer

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ptfarmer

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JBKINWA

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