Air in oil. What is normal?
- Thread starter Lrex
- Start date
There’s no water in the oil. Here is the same cup of oil after sitting. The oil level is normal.
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Excessive air in oil comes from two methods. One, too low an oil level, the oil scavenge sucks in air and churns. The other, too much oil and the crank spinning froths it up.
Russell King
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T
Think about a kid trying to get 110% of a drink out of a cup through a straw. Slurping is another way to think of it.
Russell King
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Yes.
But you may want to look at all the rubber hoses and the connection points on the suction side of the pump. There may be some issues that allow air to be sucked into the oil. The issues are loose connections, cracked hoses or leaky joints.
But honestly you have shown a cup of oil with entrained air and asked if that is normal. But you don’t say much else. Like how you got the oil out of the tractor, why you are concerned about it, why you started to even look at the oil.
I don’t have a hydrostatic drive tractor so can’t say if that is normal or not. I can say that oil returning to a transmission case may have some entrained air in it but if there is foaming that is not normal. The air should get out of the oil quickly and not foam. There are additives in the oil to help that happen. Are you using the correct type of oil? Is the tractor trying to creep foreword or backwards at all? Is there any squealing noises? How long have you noticed this happening or has it suddenly started? Has anything happened to the tractor and then this started?
But you may want to look at all the rubber hoses and the connection points on the suction side of the pump. There may be some issues that allow air to be sucked into the oil. The issues are loose connections, cracked hoses or leaky joints.
But honestly you have shown a cup of oil with entrained air and asked if that is normal. But you don’t say much else. Like how you got the oil out of the tractor, why you are concerned about it, why you started to even look at the oil.
I don’t have a hydrostatic drive tractor so can’t say if that is normal or not. I can say that oil returning to a transmission case may have some entrained air in it but if there is foaming that is not normal. The air should get out of the oil quickly and not foam. There are additives in the oil to help that happen. Are you using the correct type of oil? Is the tractor trying to creep foreword or backwards at all? Is there any squealing noises? How long have you noticed this happening or has it suddenly started? Has anything happened to the tractor and then this started?
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Anytime you pump oil through a hydraulic system it creates aeration. Lots of factors affect the amount of aeration including oil temperature, sump size relative to flow rate, orifice sizes, etc. Some aeration is normal and I think you are looking for a problem where none exists.
Dan
Dan
I respect Dans’ expertise with hydraulic systems but I strongly disagree that “Anytime you pump oil through a hydraulic system it creates aeration”.
In a healthy system NO aeration should occur. Aeration is harmful and is the result of either low supply in the sump (where the pump sucks air up with the oil)…Or, a leak in the suction-side of the system. Look for a leak or a break between the oil in the sump and the pump.…or a leak or crack at/in the pump itself.
(Very rarely oil being injected into an existing sump of oil can inject air into the system, …but that is not something to be found in a closed system.)
Nonsense. Do a little research. Or a sumple experiment like filling a bucket with a garden hose.
Gas entrainment is an unavoidable phenomenon in any hydraulic system where fluid is being pumped at high pressure and flow rates. Limiting it is a primary concern when designing any system.
In addition to ordinary turbulence the cavitation mentioned below occurs at many places in a high pressure high flow system, not just the pump. Cavitation and resultant aeration occurs in any high shear region - e.g flow restrictions like the glands on valve spools.
All of that adds up to bubbles in the sump where the bubbles are given time to dissipate.
Causes of Air Entrainment
- Suction Leaks: Loose hose clamps, microscopic cracks, or worn pump shaft seals allow the intake side to pull air directly into the fluid. [1, 2]
- Reservoir Issues: Low oil levels create vortices that suck surface air down, while undersized tanks or missing internal baffles give bubbles too little time to escape. [1, 2]
- Turbulent Returns: High-velocity oil or return lines dumping fluid above the tank level cause splashing and constant aeration. [1, 2]
- Pressure Drops: Sudden pressure releases or restrictions at the pump inlet cause dissolved air to turn into gaseous bubbles. [1, 2]
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North Idaho Wolfman
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Looks normal to me too.
Depending on how you got the sample that might explain some of it too.
Depending on how you got the sample that might explain some of it too.
Runs With Scissors
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Maybe I missed it, but is there a problem the OP is trying to solve? (i.e. FEL not working, strange noise, tractor not moving?????)
I mean, no disrespect intended, but how/why would someone take a sample of their hydraulic fluid?....Just for "kicks and giggles"?
Just curious.
I mean, no disrespect intended, but how/why would someone take a sample of their hydraulic fluid?....Just for "kicks and giggles"?
Just curious.