Hydraulic fluid foaming?

[J_J]

I can see that this is one of those cases where a picture is worth a thousand words.

Should I hear a sucking sound or see any fluid leaking with a suction leak? Would the power of the suction leak be based only on engine RPM since the pump is in theory always moving the same amount of fluid?

Thinking I can go around with an eye dropper type device to try and check connections. Is that a decent idea?

No, you won't hear a sucking sound unless you have a severe leak. and then you will really see a lot of bubbles, and foam.

If you have an 8 GPM pump,at 3000 psi, at max RPM, that only means that at the highest RPM , and you have enough resistance to the pressure, then you will produce a pressure of 3000 psi. At low RPM, you might be only 2 GPM, and if you have some resistance like a cylinder lifting a half load, then you might see 1500 psi. A hydraulic gage is very handy to have and use.

 

[IslandTractor]

I don't know if this is relevant as you have double checked your HST fluid levels but I had a lot of foaming one day with my CK20 when I inadvertently overfilled the HST oil reservoir. In my case it was due to checking the fluid level before running the motor then adding fluid when it appeared to be low. It doesn't sound like that is your issue though. Nevertheless, it does seem that one cause of foaming (my fluid was a light brown is was so foamed after mowing) is too much HST oil. I never saw foam again after realizing my error and draining the excess oil.

 

[Highbeam]

Hi IT, how overfull was it to cause the foam? I am a healthy 1/4" above the full mark when the 3ph is at half and the loader is on the ground.

 

[J_J]

Are you checking your fluid cold or hot. It will expand and show more on the dipstick when hot?

 

[Highbeam]

Checking when warm, we haven't had enough grass grow yet to really heat it up.

 

[IslandTractor]

Hi IT, how overfull was it to cause the foam? I am a healthy 1/4" above the full mark when the 3ph is at half and the loader is on the ground.

I had checked the fluid before starting the engine that day and noted the level was very low (below minimum). Loader would have been on the ground and 3PT would also have been down with a mower on it. I therefore filled it to the max normal level and then just started and used the tractor without rechecking. I imagine that the original level was probably within the normal range really and that it was just the vacuum lock or whatever phenomenon is responsible for giving low readings before starting the engine. I therefore think I added about a quart or maybe a bit more than needed so I'd guess there was an extra quart above max.

I did not notice anything wrong until I stopped mowing a couple of hours later and saw a small amount of HST oil bubbling out of the dipstick tube. When I checked the level I immediately saw the foamy light brown fluid full up the dipstick tube. I muttered and scratched my head but did not check again until the next morning when the foam was gone and I saw that the reservoir was way overfull. After draining out about a quart all was normal afterwards.

 

[TBDonnelly]

I had checked the fluid before starting the engine that day and noted the level was very low (below minimum). Loader would have been on the ground and 3PT would also have been down with a mower on it. I therefore filled it to the max normal level and then just started and used the tractor without rechecking. I imagine that the original level was probably within the normal range really and that it was just the vacuum lock or whatever phenomenon is responsible for giving low readings before starting the engine. I therefore think I added about a quart or maybe a bit more than needed so I'd guess there was an extra quart above max.

I did not notice anything wrong until I stopped mowing a couple of hours later and saw a small amount of HST oil bubbling out of the dipstick tube. When I checked the level I immediately saw the foamy light brown fluid full up the dipstick tube. I muttered and scratched my head but did not check again until the next morning when the foam was gone and I saw that the reservoir was way overfull. After draining out about a quart all was normal afterwards.

You have me wondering if your HST vent may have been plugged...

Don

 

[Highbeam]

Not sure if this would cause foam but, have you blown out the vent on the HST tranny lately?

Don

No, never, I'll get right on that. The red rubber has faded into pink and there is an oily dark spot below the little outlet from the vapor I assumed. Easy to clear and check.

I think I will plan on removing some fluid soon to get the fluid to within the dipstick range. As I recall, the final drives had only a small amount of UTF in them so it should be easy to control the release.

 

[TBDonnelly]

No, never, I'll get right on that. The red rubber has faded into pink and there is an oily dark spot below the little outlet from the vapor I assumed. Easy to clear and check.

In case anyone is wondering where the vent on a CK30 HST is, here's a couple pictures.

Don

 

[IslandTractor]

You have me wondering if your HST vent may have been plugged...

Don

If a clogged vent would cause there to be "hydro fluid lock" as the tranny cooled down the night before I checked the level cold then perhaps that was a factor. That might have mislead me into thinking the level was low. I would have removed the cap/vent in order to put more fluid in and perhaps that cleared any clog. I did not specifically look for a clog or notice one.