Foamy hydraulic oil?

davesisk · May 10, 2003

Just curious. When I open the hydraulic tank after the machine has been running and is even a little hot, the hydraulic oil is quite "foamy" (for lack of a better word). I can always see bubbles floating on the surface. When cold, the oil looks very clean and clear.

Does anyone else notice anything similar? I don't think the cause is excessive temperature, because I get this even when the oil isn't all that hot. I'm wondering if it's possibly dirt or impurities in the oil. I have never changed the hydraulic oil since I've had the machine (about 1.25 years now). Does anyone notice anything similar with the new machines that have fresh oil in them?

Any other thoughts?

Thx,
Dave

Bob999 · May 11, 2003

Sounds like air in the hydraulic system. That might be natural since you had to open the system to install the selector valve. If it persists I suggest you check all suction lines very carefully for a possible leak.

duane · May 11, 2003

Dave,

I too, see some small air bubbles on top of the oil. As Bob, indicated, you may have more than normal due to work you just did. Air coming out of solution is normal, and according to what I have read and discussed with manufacturers, one of the design criteria for a reservoir is to allow proper aeration. I also see it on our hydraulic equipment at work. In the vented PT reservoir, air is always in contact with the oil surface.

Duane

MossRoad · May 11, 2003

<font color="blue"> I have never changed the hydraulic oil since I've had the machine (about 1.25 years now). </font>

Even though it is clean and clear, 10 gallons of 10W40 won't cost that much. And all it can do is prolong the life of the beast. /forums/images/graemlins/laugh.gif

As for the air bubbles, I don't know. I just washed mine up two days ago and need to do the 100 hour maintenance the next day I have free. After I change the filter and purge the system, I'll mow with it and then check the reservoir and let you know what I see.

ernemats · May 11, 2003

I used my 422 today to do some mowing the grass was very high, thick and wet. I checked the resivour after mowing for about 30 minutes the cooler fan was running ,and there would be some air bubbles flowing by every now and then not what I would call foaming. I have had my 422 for a little over 3 years and about 440 hours on it and I have never changed the oil in the hydraulics. I have just changed filters, the oil still looks good and clear .

wasabi · May 12, 2003

Last fall I discovered a small hole in the main suction hose from the tank to the pump. One of the indications that caused me to poke around and check al the hoses was foamy oil in the hydraulic tank. PT cautions that the pump is very sensitive to dirt and or air in the oil. Best check carefully.

davesisk · May 12, 2003

Wasabi:

I would certainly hate to burn up the $1200 hydrostatic drive pump in mine. For all I know, that suction hose might be as old as the machine itself (13 years).

What did you do to find that hole in the suction hose?

Thx,
Dave

wasabi · May 12, 2003

Nothing really. Actually, one of the fellows working for me pointed it out and deserves full credit. After seeing oil on the surface of the main hose near the "hinge" of the tractor, he traced it back to the small hole. After he pointed that out I also noticed a hissing sound (wearing my curiously sensitive Pro-ears) when the unit was was under power and then found the foamy oil. I also noticed that the main hose appeared a bit "brittle" (surface cracked when I pushed on it). After that I essentially stopped using the PT until I could get it repaired as I was paranoid about trashing the pump. (I used two hose clamps and piece of rubber tubing to staunch the fairly minor oil flow so I could drive it the 1.5 miles out my lane and load it on the trailer for the journey to PT)

davesisk · May 13, 2003

Well, I started the tractor up this morning and checked the oil in the tank. Cold but at full throttle, I didn't see any bubbles. So, sounds like this may be temperature related moreso than a potentially leaky suction hose? (Of course, the suction hose might only become leaky when the oil in it heats up...that's a thought). I couldn't hear anything that distinctly sounded like hissing. I was on my way to work, so I didn't want to get greasy and dirty, but I'll give the suction hoses a good look over the weekend.

Any other thoughts on things I should check?

Thx!
Dave

davesisk · May 13, 2003

One more thought here....oil is thicker when it's cold than when it's hot. So, if there's a leak in the suction hose, I'd expect to see more bubbles when the oil is cold, because it's thicker and harder to suck, thus allowing more air to be sucked into the mix. Conversely, I'd expect less bubbles when it warmed up. Does anyone who has experienced this agree or disagree?

Of course, I guess a hole in the hose could expand as the hose theoretically expands as it warms up...so maybe the above thought is totally invalid...?

Dave