JD 310D 1991, foam oil in Hydraulic Reservoir

[Southbus]

Hello my friends, first, thank you for allowing me to enter this community, I'm Southbus, i live in Chile a long and flat country in Southamerica, i have a old but strong John Deere 310D 4x4 Backhoe.

The past week a lot of oil foam go out from the reservoir when uncover to inspect hydraulic oil level,
Large air bubbles emerge from the bottom of the tank, after about 10 minutes the level of the foam decreases but the oil stay with gray colour, i think millions of small bubbles are mixed with the oil. When the oil take work Temp i can work but i feel lost of performance, some low noise...
2nd day the same, the turbulence decreases when oil take temperature,

After a visual inspection there are no leaks in the large hose that feeds the pump, either in the joints or in the pump itself.
Today i decided to replace all hydraulic oil from the reservoir, new filter element, I have tightened all the clamps...
Long work day but the problem is still there...

Now I only keep to the minimum the level in deposit to avoid that I go out when I start cold.

I appreciate your help,
Regards from Chile

 

[Delmer]

Welcome to the forum. Maybe you mean a long and narrow country? From what I've heard your country is anything but flat.

Have you been using this backhoe for a while and the foaming just started a week ago? What kind of hydraulic oil did you use when you changed it?

The two most common causes of foaming oil are contamination (water will reduce the effectiveness of anti foaming additives, or something like that), or a suction leak. Large air bubbles almost has to be an air leak somewhere. You could try pressurizing the hydraulic reservoir LIGHTLY to see if it makes any leaks show up. If you suspect water in the oil, you can drip a drop on a hot steel surface and see if it sputters or just smokes. Water will make the oil pop.

 

[Southbus]

Delmer, thanks for you answer, I used the backhoe during this year without problems, the foam start a week ago, yesterday drain the hydraulic oil with 800 hours approx and replace it with new oil ISO 68, and new Hydraulic filter. The large hose between the reservoir and the pump looks good and no visible leaks but it is hard as a rock.
Do you think that too much air in the reservoir is caused by suction leaks in the hose or pump?
There are also fluid returns from the filter and the cooler, Could these returns also suck air?

 

[Southbus]

The problem increases when it is cold in the first start in the morning

 

[Delmer]

...it is hard as a rock.
Do you think that too much air in the reservoir is caused by suction leaks in the hose or pump?

The other returns won't be leaking air, there's no suction. The hard suction hose is probably cracked, with THAT much air leaking, I'd smear the hose with grease while somebody watches the tank from the view of that video, IF you want to be sure before you replace it.

 

[Plongson]

Do the hot plate "crackle" test first. If you suspect contamination in the form of water or something else you can send off a sample for analysis to someplace like Blackstone...or or any local machinery dealer.

Like Delmer said, foaming of hydraulic fluid is usually caused by contamination, mixing non-compatible fluids or air entrainment. Worn out pumps and cavitation might also be considered but that's getting a bit deep at this point. Look for the easiest and most likely culprits first.

An old and hard suction hose can really be a beast to replace. It took me 2 days to wrestle in a new one on my 210LE.

 

[Southbus]

I appreciate your advice, I have washed the whole place and now I prepare to change the big hose, I hope that is the fault, in my country there are very few John Deere spare parts and they are very expensive, not to think that the pump is bad.

PD, A thousand apologies for my "southern" English

 

[Delmer]

Just be grateful that you're not getting advice in my "Spanish".

Do you have a hydraulics shop that can get you the correct hydraulic suction hose for this? Or maybe your Deere dealer is the best place?

I don't think the pump is bad, usually the hydraulics will get weak when really hot if the pump is worn out.

 

[Southbus]

Bad news from south
I have replaced the hard hose between the hydraulic reservoir and the pump and the problem continues, many bubbles in the tank when I run engine, I run out of ideas. Now I have removed the counterweight of the front and I have the hydraulic pump in sight, I see a small screw on one side that seems to let air out, I do not see oil moisture in the pump body.

 

[92U 3406]

I'm more familiar with the newer Deere/Hitachi stuff but I'll take a crack at it.

On a lot of equipment there would be a steel pipe that joins the rubber suction line to the hydraulic pump. Usually the connection between the steel pipe and the pump is a flange type with an o-ring seal. If you have something like that did you replace the o-ring there?

Does this unit have a pilot pump? If so did you check the inlet connections on it as well?

 

[Plongson]

Did you do the hot plate "Crackel" test?? Most easy...

 

[Delmer]

That's not a small amount of air getting into the oil over time. That's a huge amount of air leakage, if you have a helper to watch the reservoir, you could use an oil can to go over the suspected joints/seals until the air stops, it might only stop for a bit. OR, put a few PSI of air pressure in the hydraulic reservoir and see if you can get it to leak.

Concentrate on the suction side of the hydraulic pump, including the pump shaft seal.