Buzzing From Hydraulic Pipe - Cause for Concern?

[mercdv]

You probably introduced some air into the system when you ran the attachments with the drain open. The fluid coming out had to be replaced by something (that something being air). It should bleed itself out over a short period of time. I'd run it a bit but make sure you don't do any heavy work and stay off hills until you know most of the air is out. If the bubbles don't start disappearing, something has failed and is letting air into the system.

 

[Leejohn]

I have seen this a number of times and it is good reading on hyd oil.

 

[Coyote machine]

Good paragraph structure! A+
Thanks, it makes reading one's post soo much better.

As far as changing the new filter out I wouldn't right yet. By leaving the plugs out and running the engine you most likely did introduce unwanted air into the system. I'd wait and use the tractor lightly until all the fluid has settled out the air. I'd also use the implements that had the 80-90 run through their hoses so it can be mixed in with the new correct HST/UTF, AND run through your current new filter. Let the current filter work the mix of the new and wrong fluid until it's well diluted. Then, after a week or two, maybe screw on a new filter to keep 'cleaning out' whatever remains of the 80/90W.

I also suggest asking here on TBN before going rogue and doing something like starting the tractor with the plugs out of the transmission. Likely you would have been advised to not do so.

In general, most long time tractor owners working with HSTs are aware that even when using the correct fluid, when it comes to do an entire system fluid change, one never really gets it all because of fluid left in hoses and hydraulic cylinders. It's one of the reasons to change fluids regularly, it and the HST filters do a good job of keeping contaminants out of a darn near surgically clean environment.

What you don't want to see is milky hydraulic fluid. That would indicate water contamination. Air is not good as already addressed, but what you allowed to enter is not the same as an air infiltration leak happening constantly or intermittently.

Your buzzing noise may continue to dissipate over time as things in your HST settle down. Remind us what # of hours was on the clock when you changed the fluid originally? How many hours have you put on it since?

What possessed you to change your HST fluid to begin with?
Are OEM Mitsu filters not available via your dealer or some other source?
I checked the filter link from your first post, and it came up with a UK address- aren't you in Wiscon? I'm getting confused by all the inconsistencies....
Please clarify the answers so we all can be on the same page.
Am I understanding that you bought the tractor new -what year?
And to best guess you did not hear the buzzing until after you put the 80-90 WT in, with a filter change at that time.

 

[ovrszd]

My wild side says, problem not solved. I'm trying real hard, but try as I might, I cannot swallow that 80-90 versus Universal Hydraulic Fluid is causing this.

Yes, I'll totally accept defeat when this is proven to me.

 

[Coyote machine]

My wild side says, problem not solved. I'm trying real hard, but try as I might, I cannot swallow that 80-90 versus Universal Hydraulic Fluid is causing this.

Yes, I'll totally accept defeat when this is proven to me.

I tend to agree the noise could be something totally unrelated, but your post got me thinking so I adjusted my post above to get a clearer picture of the timeframe of wrong fluid and noise first heard by OP.

I theorize so far, assuming I have the correct info- that the noise was NOT present from day 1, but did begin AFTER the fluid was installed and due to it's wrong viscosity and designed for an entirely different application, the HST trans AND filter could not handle the need to pass thick 'molasses' through micronic sized filter media, and the transmission could not achieve the correct pressures, etc. In fact, it's possible the noise is the result of an artificially induced overpressure as a result of the fluid not being able to pass through the HST as it would with the correct UTF....
I'm not a hydraulics engineer- next life, but it's possible the restriction could cause too low pressures too in some crucial part(s) of the HST passages/filter - I just don't know enough to know which way it might have manifested.

BUT, it's entirely possible using a gauge set to see where the pressures are now could help further diagnose/render a viable solution to the noise/function of the HST now and going forward?

What thinks you folks reading this thread?

 

[mercdv]

My wild side says, problem not solved. I'm trying real hard, but try as I might, I cannot swallow that 80-90 versus Universal Hydraulic Fluid is causing this.

Yes, I'll totally accept defeat when this is proven to me.

I would certainly agree with this statement if the noise doesn't settle down after running it a bit. There are a lot of reasons a noise can be created in a hydraulic system and the wrong oil can certainly be one of them. Even with the right oil, there can be many other reasons. Just as an idea of how one thing being off can cause noise problems in a hydraulic system, check out this.

Noise control in hydraulic systems | Hydraulics & Pneumatics

If the tractor doesn't return to the original noise level after you are confident the bad oil is out, I'd take ovrszd's advice and start looking for another cause. Do you have anyone near you that has knowledge of hydraulic systems that can help? I'd drop by and help take a look at it but I'm WAY to far away from you.

 

[Dave M7040]

I think you need to look at the original schematic you posted with the yellow highlights

It shows the HST oil flow going to the filter not sucking from the filter.

It is hard to tell what exactly is in the green circle I made but it seems to be where both HST and hydraulic systems suck their oil.

Checking it out for restrictions might be wise.

The metal particles. Use a magnet to determine is they are iron or steel or alternatively if not magnetic, aluminum.
A fridge magnet is all you need.

Dave M7040

 

[Fallon]

I tend to agree the noise could be something totally unrelated, but your post got me thinking so I adjusted my post above to get a clearer picture of the timeframe of wrong fluid and noise first heard by OP.

I theorize so far, assuming I have the correct info- that the noise was NOT present from day 1, but did begin AFTER the fluid was installed and due to it's wrong viscosity and designed for an entirely different application, the HST trans AND filter could not handle the need to pass thick 'molasses' through micronic sized filter media, and the transmission could not achieve the correct pressures, etc. In fact, it's possible the noise is the result of an artificially induced overpressure as a result of the fluid not being able to pass through the HST as it would with the correct UTF....
I'm not a hydraulics engineer- next life, but it's possible the restriction could cause too low pressures too in some crucial part(s) of the HST passages/filter - I just don't know enough to know which way it might have manifested.

BUT, it's entirely possible using a gauge set to see where the pressures are now could help further diagnose/render a viable solution to the noise/function of the HST now and going forward?

What thinks you folks reading this thread?

The HST pump & motor combo are a unique unit completely separate from the rest of the hydraulic system. Other than they share a common sump. HST pressure is going to be unrelated to loader or 3pt pressure. I'm not sure if your HST system has an easily accessible pressure port.

 

[oldnslo]

Sconnie,
On your first post you stated the noise stops when you push in the clutch. Does the clutch provide the input power to the HST? I know it does on my Branson.

Does the noise change with engine RPM? I.e. from idle to half throttle.

Does the tractor drive properly now with the AW46 oil? If yes the noise change while driving?

If you hold onto the tube can you feel it vibrating?

Reason for all these questions is that there is a possibility that the charge pump and or charge relief are produce some noise ripple that is being transmitted through the tube in question.

 

[sconnie]

First off thanks for all the responses. I do not have an update on the noise dissipation as I've not had a chance to start it up and use it these past few days. I'm hoping Friday but if not, Sunday for sure. I'll post back on how it sounds.

To clarify a few questions:
-I bought the tractor used with 636 hours. right now I'm at 676.
-I do not remember the buzzing noise occurring at the time of purchase. Again, I'm hesitant to say it 100% wasn't there because of unfamiliarity with the machine but I'm fairly certain it was not present until the fluid/filter change.
-I decided to change the all the fluid because I wanted to go through the whole tractor and start with everything fresh so I knew exactly when it had been changed.
-UK address on link was just a reference page to see equivalents for filters.
-I believe the clutch does provide power to the HST, but I will have to test it this weekend to varify.
-If I put my hand on the pipe, I can feel very small vibrations.
-The noise does seem to be related to engine rpms, but at a certain point >15 maybe, it all sounds the same.
-After changing the fluid, i noticed pushing the pedal into the forward position and making the initial transition from stopped to moving slowly forward is much easier. Before, i might have to press the pedal into the reverse position for a second and then try the front position because I was not able to push it into the forward position. This symptom was one of the red flags that led me to wonder if some thing was wrong.

Dave, good catch on the hydraulic diagram. I thought the flow in that pipe was out from the filter, but that arrow relieves my worries that the filter is clogged and causing tough suction.

I will update with more information once I'm able to run it around a little get more specifics.

Thanks again everyone.