Air in hydrostatic fluid

Anonymous Poster · May 19, 2003

I have a B7200HST. When changing the hydrostatic fluid, I noticed that it was milky looking when drained (I had run it a few minutes to warm it up). I put the new oil in (clear from the can), ran it a few minutes and this new oil also had a milky look which I determined was air in the oil. The tractor seems to perform fine but I am concerned that there may be a problem that may cause future damage. Does anyone know if this is normal? If not, what may be causing it?

Anonymous Poster · May 19, 2003

If there is actually air whipped into your hydraulic fluid, just about the only place it could enter the system is between the hydraulic reservoir and the pump or pumps which pressurize the hydraulic fluid and send it out under pressure. A hole/loose fiting between the reservoir and the pump will allow air to be sucked into the system, and usually causes noisy pump operation and a lack of power and slow response to the pedal in an HST. The first thing people will think of when they hear "milky fluid" will be water in the hydraulic fluid. Are you sure the cause of the milkiness was air? If you haven't recycled your old fluid yet, check again carefully. If it is/was water, a single oil change may still leave a significant amount of water in the system. And if it is water, you WILL have to figure out where and how it's getting into the reservoir. Wash your tractor with the reservoir fill cap loose? Best of luck tracing the problem.
Bernie

Anonymous Poster · May 19, 2003

Thanks for the input. I'm almost positive that it is not water. I'll check for leaks in my hydraulic lines but fluid is not leaking anywhere. The HST has always had a "whine" but I have been told that it is normal. By the way, there are 615 hours on this unit for what that is worth.

5030 · May 19, 2003

If you can't figure out if it is water or air, send a sample of the fluid out for analysis. Your local friendly New Holland dealer has a test kit that you can buy from him that will have a pre-paid sample bottle in it. Put a sample of theoil in the bottle and send it off to the address provided. The lab will do a spectroscopic analysis of the oil and tell you exactly what is in it. It will list the oil, it's additives and any foreign substances. It's a good idea to do a spectroscopic analysis of your engine oil once in a while too. It's a good indicator of the condition of your engine, especially the bearings and injectors.

Anonymous Poster · May 19, 2003

A small hole or loose fitting between the reservoir and your pump(s) wouldn't necessairly show up as a leak when the tractor isn't running. The line from the reservoir to the pump(s) is under negative pressure when the tractor is running, and (obviously) that's when air might be being sucked into the system. Once the tractor is shut off, the line is under no pressure, and oil leaking out may never be evident. As a matter of fact, if there is a hole or loose fitting above the level of fluid back in the reservoir, oil can just drain back into the reservoir, and you could never see a leak. (Kind of like drinking water through a straw with a hole in it. Once you stop sucking, air enters through the hole, the water flows back into the glass, and you never see water on the outside of the straw. But you do get alot of air mixed with water in your mouth when you try to drink!) I'm not familiar with how the B7200 is plumbed, so maybe someone who owns one can tell you where to begin checking and where the reservoir to pump hydraulic lines are located. The only other possibility I can think of for getting air churned into the hydraulic fluid is if a pressurized return line to the reservoir is squirting oil back into the reservoir above the level of the fluid. (Kind of like squirting water into a bucket with a garden hose.) This would churn the hydraulic fluid and cause a good deal of air bubbles to get into the fluid. But since tractor manufacturers don't want air bubbles in the hydraulic fluid either, they take steps to avoid this happening. When you drained the fluid, were the bubbles dispersed throughout the oil, or did you only notice them in the last gallon or so to drain out of the tractor? Perhaps a small amount of air bubbles which slowly rise to the top of the reservoir is normal in a B7200 (although I've never noticed any air bubbles in the hydraulic fluid of my two JD tractors). If there were air throughout the fluid, I'd be concerned, too. But, again, rule out the possibility of any water contamination. Hopefully, someone on the board will have seen this problem before and be more helpful. Best of luck.
Bernie

Anonymous Poster · May 19, 2003

At the least, take a sample of the oil when it is milky, put it in a jar and check it after a while. If it is entrained air, it will slowly migrate out, and the oil should clear. You may have a clogged pickup, or a leak in the pump suction, or the oil level is low. If it is water, it will clear somewhat, but leave a layer of emulsified oil on top (milky gook). Are you sure the fluid wasn't low when you changed it? My old power king leaked oil like a pig in a jungle, and the fluid was always low. Scared me the 1st time I changed it when it came out looking like sloppy whipped cream.
Hope this helps. Keep us posted.
DaveL

Anonymous Poster · May 20, 2003

Thanks to everyone for the suggestions. No, the oil was not low when it was changed. As a matter of fact the new oil looked the same when it was checked after the change and after running it for a few minutes. If anyone knows about the plumbing on this unit and has a suggestion as to where to check, I would appreciate the input. There is no seperate reservoir for the oil but you just pour it into the top of the transmission. There is a fill plug next to the dip stick right under the front of the seat.