Foaming Hydraulic Fluid

BarnabyHooge · Nov 3, 2017

Installing this 703 loader has been pretty fun. It's taken just about every tool, trick, and lesson I've learned. That said, I'm just about ready for this thing to work.

I'm now getting foamy hydraulic fluid. Any lift is erratic and the cylinders are soft/bounce. When brought all the way down, it gushes foam from the breather.

It's filled to an appropriate level with new fluid. I understand the cause is likely a leak on the suction side, but I don't see anything. The frame to pump looks really tight, and the return from the controller to the frame looks good as well.

Any tips on finding where the air is getting in?

Larry NCKS · Nov 3, 2017

Are you using hydraulic fluid that's spec'd for that application?

BarnabyHooge · Nov 3, 2017

I believe so. I'm using the premium trans/hydraulic from TSC. I had read in a couple different spots it would work, and preferred it since I use it in the tractor anyway.

sotxbill · Nov 4, 2017

then your sucking air or cavitating?

does it only do it when your lowering the cyl? or when your not using the hydraulics? Try to figure this out and it will lead you to the problem.

If all the time.. suspect pump, relief valve, feed line and return line for the problem.. If only in certain cyl movement, suspect blow seals and air getting into system that way.

When lowering the weight will push it down faster than the fluid can go to the other side, assuming you have two way cyls... and not gravity drop.. if you have gravity drop, your cyl seals are leaking and letting air in... or the "return to tank" is problem.

BarnabyHooge · Nov 4, 2017

I'm not hearing any cavitating, but the cyl do seem to stall out for brief periods when I try to raise it up. Not sure if that would be a symptom of cavitating.

The down movement is steady, and it only gushes the foamy fluid when it comes all the way to the down position. If not in use or going up, or coming down only part of the way, there is no gushing. The cylinders are double action.

Sorry for my ignorance, are the blow seals part of the cyl?

Larry NCKS · Nov 4, 2017

(quoted from post at 12:27:33 11/04/17) I'm not hearing any cavitating, but the cyl do seem to stall out for brief periods when I try to raise it up. Not sure if that would be a symptom of cavitating.

The down movement is steady, and it only gushes the foamy fluid when it comes all the way to the down position. If not in use or going up, or coming down only part of the way, there is no gushing. The cylinders are double action.

Sorry for my ignorance, are the blow seals part of the cyl?

I think his blow seals were intended to be blown seals.

Here's what I now suspect given this latest information. You have trapped air in your lift (raise) lines or cylinders. That accounts for the "stall out" on your raise. Air escaping out of the lift side into the reservoir at complete drop accounts for your foaminess. It should eventually all bleed out and be fine. you can hasten the bleed by loosening fittings on the raise hoses as you drop the loader if you need to.

BarnabyHooge · Nov 4, 2017

(quoted from post at 10:43:28 11/04/17)

I think his blow seals were intended to be blown seals.

- Ha, I probably should have figured that one out myself...

Would trapped air in the lift cause sponginess in the whole system? The bucket doesn't cause the gushing foam, but it doesn't hold tight as it should either.

I should head to the library, see if I can't find a book on basic hydraulics.

Thanks for the input, it's greatly appreciated.

Sean in PA · Nov 4, 2017

Any line, hose or connection that is too restricted can cause cavitation bubbles. The pump itself might even have something foreign inside blocking something up causing cavitation.

Foaming Hydraulic Fluid

BarnabyHooge

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Larry NCKS

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BarnabyHooge

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sotxbill

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BarnabyHooge

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Larry NCKS

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Sean in PA

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