Water in hydraulic fluid..

[skeer]

So yesterday was rolling the driveway with the Cub and a bump mustve dislodged the dipstick.. because I noticed the whole *** end wet. Promptly parked and pulled the drain plug.. maybe a 1/4 cup or so of water preceded the oil.
IDK where the pick up tube is inside this unit but I assume some water got into the pump. Best way to make sure it's cleaned out I figure is to maybe fill it up most of the way and let it run for 20-30 seconds then stop and drain again. That sound decent?

 

[larry_g]

There are a lot of tractor models under the CUB name. What specific tractor do you have? Is the hydraulic system separate, is it a transaxle where the fluid is used for both the trans and hydraulic, is it standard shift or hydrostatic?

Me, I'd run it and see if the fluid turns milky. If it does then change it along with the filters.

 

[skeer]

Yeah sorry, model 3184. One of the last models before MTD bought 'em out. Anyway I threw a couple quarts in there and ran it for about 30 seconds or so then killed and re-drained. Had a small bit of froth come out.

 

[Firebrick43]

Yeah sorry, model 3184. One of the last models before MTD bought 'em out. Anyway I threw a couple quarts in there and ran it for about 30 seconds or so then killed and re-drained. Had a small bit of froth come out.

MTD bought out the cub cadet brand in 1984 and continued building the 82 series for a few years with only minor changes (changing the transmission case and axle housing to aluminum), long before your tractor was built

As far as water in the hyd oil. I am surprised it wasn't emulsified but the sump you drained did its job. Water vapor finds its way in via the vent and as the case heats and cools due to air temp the vapor condenses and precipitates out.

We always drain the sumps every spring of water on our tractors by loosening the drain plug (while cold) and keep backing it out while holding it and you can drain just the water and just as soon as the oil comes out screw the plug back in. The amount you drained isn't that uncommon. I wouldn't fill and flush again unless the oil on the dipstick is cloudy with emulsified oil after running it.

How long does it take you to mow? Hydraulic system designers want the oil to be a 180-200 degrees typically on purpose so any water in the oil is vaporized while its running and expelled via vapor out the vent. Just like those that drive in town only, it your yard is small and the machine doesn't reach operating temps for any extended time you should drain more often.

 

[cannuck]

Different oils have very different additive packages based on what the designer specified to do what he/she wanted. Some have emulsifiers, so the water is kept in suspension until drained with oil (typical of most motor oils) while others have demulsifiers because the want water to drop out and remain at a low point to drain or more easily knocked out by an oil treatment process. I was once paid to haul away a semi load of new oil when the engineering company building a steam turbine power station didn't understand that. Most profitable oil deal we ever had.

Back to OP: yes, drain it and refill is all you need, but doing a flush will not hurt. Water could be getting in from leak above oil level or just from condensation from air in the housings. Worth noting that one of the first things you do when going out to fly an airplane is drain the water out of the tanks. Aluminum tanks are especially efficient at condensing moisture from the air space above the fuel - and nobody ever flushes the system - just drain until water doesn't show up in your sample cup.

 

[Firebrick43]

The cub cadet horizontal shaft hydrostat transmissions don’t have issues from rain or wash water getting into them because of their design. The gear drives did if the shift boot was torn.

 

[skeer]

Yeah insofar as how this water got in there it was definitely thrown towards the unplugged dipstick by the lawn roller splashing. Either thanks guy, I'm sure it's fine now.

 

[nadogail]

I have worked in a Rubber Parts Manufacturing Plant and our Hydraulic Fluid was a mixture of Water and Soluble Oil.
That probably is irrelevant to your situation, but AFAIK, Water was the original hydraulic fluid.