Buzzing From Hydraulic Pipe - Cause for Concern?

[sconnie]

Hi all,
Bought my first tractor last summer, a little Mitsubishi MT180HD and it has been great for around the house so far. When I bought it, I went through and changed the coolant, engine oil & trans/hyd. fluid. Sometime later, I was operating the tractor when I noticed this buzzing/ringing sound coming down near my feet. After listening closer I found the pipe it is coming from (diagram below). The buzz/ring is not audible immediately upon startup. However, within 10-15 seconds it starts to build until it is at the level illustrated in the video (link attached). When the clutch is depressed, the buzz/ring stops.
I replaced the hydraulic fluid with Mystik 80w-90 from Farm & Fleet (image below) and replaced the hydraulic filter with a CAT 4T-6915 (manual calls for Donaldson P556005 but I could not find any around. I found several websites saying the CAT filter was approved equivalent, link below). I removed the hydraulic filter screen and cleaned very gently with diesel fuel and starting fluid. I was careful not to damage this delicate mesh. I do not remember this sound when I first bought the tractor, but then again I was new to the machine and also very excited to use it so there is the possibility that I was just oblivious to the sound at first.
I realize that tractors are big machines with a lot of moving parts & sounds, but this one seems distinct to me. I was hoping to get your opinions on the following:
1. First and foremost: Is this a concerning sound that requires immediate attention?
2. What is causing this sound?
3. If this needs to be addressed, what can I do to fix it?
After doing research my fear is that it could be cavitation and running the tractor any longer could damage the hydraulic pump. However the videos I've watched on cavitation do not sound the same as what I'm hearing on my tractor. I don't know if this is due to the majority of cavitation videos I found being on large scale industrial type hydraulic systems vs a little 18 hp tractor?
Below are pictures of the referenced information and a link to the video of this buzzing sound.
If I've forgotten to include any information please let me know and I'll respond.
Thanks in advance for the help!
Sconnie

Location of pipe producing buzzing sound


CAT approved equivalent for Donaldson p556005
FBW-BT8314 FILTER-Hydraulic(Spin On) - Buy Online - Next Day Delivery

Manual info on hydraulic fluid



80w-90 from Farm and Fleet


Video of tractor buzzing/whirring noise
Mitsubishi MT180HD Hydraulic Buzzing - YouTube

 

[oldnslo]

sconnie,
I suspect the 80W - 90 fluid is not the correct fluid for your hydraulic system. Most tractors today use a universal hydraulic & transmission fluid the is more like an SAE 20 weight. I would recommend looking for any information on the fluid type recommended by Mitsubishi.

Buzzing is potentially from the pump cavitating (starving for oil) which will destroy the pump. You may have to replace both the oil and filter.

 

[feasant]

do you have the old oil you drained out? if so, compare. i'm thinking the same. you used the wrong oil

 

[BeezFun]

Is it possible the lube chart you have is for a geared transmission? It would be common for a geared transmission to use 80W. But the parts diagram posted indicates you have an HST, and I've never heard of an HST that uses 80W. As was pointed out, it should be calling out some kind of hydraulic fluid that's much lighter weight for the transmission. It should be easy to tell the difference when you drained it, 80W would come out like maple syrup and transmission fluid would come out like warm engine oil. I can't explain why the clutch makes the noise come and go.

 

[Dave M7040]

There is a Mitsu owner on this forum who I regard as a very knowledgeable person on this brand. Piloon.

In your shoes, in addition to accepting you likely used the wrong oil, Piloon could possibly give more specific advice if sent a PM.

The info posted sure appears to be for a manual gear type transmission not an HST. The noise you are hearing is coming from the HST suction pipe and filter which is calling HELP!!

Don't ignore it for a moment longer

Dave M7040

 

[sconnie]

Thanks all for the info.
I can come to grips with the fact i screwed up. I am just a bit confused as to where i went wrong in understanding the manual. I will read through it closer and see if i'm missing the differentiation between the hydrostatic vs geared transmission. Thanks for the advice Dave, I will shoot Piloon a PM and see if he has any advice. Very good to know it is something that should be taken care of right away. Looks like I have my project set up for the weekend.
Thanks again everyone for advice.

 

[mercdv]

According to both the manuals I found for the MT180HD it says to use TOU or EP Hydro that is GL-3 or better. I'm not sure why your manual says something different. I wonder if you have a manual from a really early model. I found both online with a quick search. One of the manuals I found had a section that listed gears/hydraulics/4-WD front axle in the same column listing 80W-90 for gears but had a line and an a asterisk that said to use the hydro oils in farm equipment transmissions. Neither manual had pages that look like the ones you posted so I'm wondering if they had a multiple manuals over the years and some are for the much older MT180HD's. Just a thought.....had to edit because I posted the wrong thoughts in my head....I do that sometimes....I don't own one of these so I can't tell you anything past the manuals I found.

 

[swnoel]

You're using the wrong hydraulic fluid...

Which Tractor Hydraulic Fluid Do I Need? | Blain's Farm & Fleet Blog

Valley Power

Q: My manual says to use gear oil in the transmission. Is this right?

A: No. The manuals were incorrect. Most Mitsubishi tractors use a single system in which the transmission uses the same fluid as the hydraulics. Use Universal Tractor Fluid, AW46 Tractor Hydraulic Oil, JD Type 303 Special Purpose oil or the equivalent. An exception to this is the Satoh S650G, S670 and ST2500. These tractors have a split system with a separate hydraulic reservoir.

 

[BeezFun]

A: No. The manuals were incorrect. Most Mitsubishi tractors use a single system ...

That's incredible, I'm surprised there hasn't been a class action lawsuit over all the dead hydraulic pumps.

 

[ovrszd]

And while on this subject, can someone show me manufacturer's evidence of the "weight" of Universal Hydraulic Fluid? This issue comes up often.

 

[sconnie]

Ha, you guys beat me to it, i was just writing a post with the screenshot below:

Ok so then I just need to get some universal AW46 fluid and a new filter and replace. I don't know why my manual isn't including the lines/asteriks you're referncing, mercdv. I have both a hard copy and an electronic copy. I have not seen any glaring differences between the two but I'll check them out again to see if either have any mention of those addenda.
Hopefully this hasn't caused any problem to the pump & the rest of the hydro system. I suppose if I find it has, keep an eye out for some questions about replacing a hydro pump on an '84 MT180HD. BTW, anyone in the market for several gallons of 80w-90 gear lube?
Thanks again for the info everyone. I really appreciate the help.

 

[Peter 315]

We use 10w motor oil for hydraulic oil in the Komatsu equipment wheel loader and excavators

 

[CincyFlyer]

You're using the wrong hydraulic fluid...

Which Tractor Hydraulic Fluid Do I Need? | Blain's Farm & Fleet Blog

Valley Power

Q: My manual says to use gear oil in the transmission. Is this right?

A: No. The manuals were incorrect. Most Mitsubishi tractors use a single system in which the transmission uses the same fluid as the hydraulics. Use Universal Tractor Fluid, AW46 Tractor Hydraulic Oil, JD Type 303 Special Purpose oil or the equivalent. An exception to this is the Satoh S650G, S670 and ST2500. These tractors have a split system with a separate hydraulic reservoir.

Yeah, the little 24 hp manual transmission Mahindra-labeled Mitsu that my brother has uses UTF, as do the shuttles and HSTs.

 

[swnoel]

Ha, you guys beat me to it, i was just writing a post with the screenshot below:
View attachment 549998
Ok so then I just need to get some universal AW46 fluid and a new filter and replace. I don't know why my manual isn't including the lines/asteriks you're referncing, mercdv. I have both a hard copy and an electronic copy. I have not seen any glaring differences between the two but I'll check them out again to see if either have any mention of those addenda.
Hopefully this hasn't caused any problem to the pump & the rest of the hydro system. I suppose if I find it has, keep an eye out for some questions about replacing a hydro pump on an '84 MT180HD. BTW, anyone in the market for several gallons of 80w-90 gear lube?
Thanks again for the info everyone. I really appreciate the help.

I'll keep my fingers crossed nothing happened. By the way it appears that AW46 is equivalent to 15w or 20w just in case.

 

[Fallon]

We use 10w motor oil for hydraulic oil in the Komatsu equipment wheel loader and excavators

There are a number of machines from big brands that spec engine oil for hydraulic oil. As far as I'm aware it's always speced way lighter than gear oil though.

Probably goes to show that squabbling over minor variations in brand isnt as relevant as most people think. As long as you are in the right ballpark it will generally do the job needed. Unless it's way to thick to be pumped.

 

[IceStationZebra]

If given the choice between engine and hydraulic oil you should always go with hydraulic. Engine oil is often listed as an acceptable alternative for those parts of world where any oil is difficult to get but hydraulic will have a better additive package and will provide more life.

Tractors usually use a universal tractor oil that is compatible with piston pumps, hypoid gears, wet clutches and brakes.

ISZ

 

[Coyote machine]

To the OP: to make reading your posts easier to read add some paragraphs rather than just running on like one long sentence.

To the issue of the correct fluid for your transmission: consider that HST transmissions have many minute passages through which fluid needs to flow very rapidly and at very high pressures. Gear oil is just that- an oil that has a heavy weight of 80-90 and is designed to do a completely different job- basically to stick to gears and keep them from wearing at mating surfaces among other specs. Totally different purposes, which do not overlap, and are NOT interchangeable.

Hydrostats are looking for, in some instances, wet brake immersion and similar needs of other components bathed in the transmission. It's all about flow, without contaminating particulate matter, temperatures inside the HST, and delivering the correct pressure to the various items sharing the fluid in question. Without the necessary flow and viscosity and pressures the HST is designed to maintain during use, the HST could easily be damaged.

My selling dealer was telling me about a case in which someone used a generic HST fluid and completely lost their brakes. The dealer switched to the correct UTF with wet brake additives included, and the brakes worked as they were designed.

BTW, I change ONLY my HST filters and have NEVER changed out my HST fluid in over 9 years and 1500+ hours on two Kioti HST transmissions; per my dealer's recommendation. I trust his experience and judgement on this.

You however, MUST get the correct fluid in your HST without delay. The HST filters are NOT designed to handle the viscosity of the gear oil you have in place currently; a definite factor in the noise you are hearing. Your HST is screaming for the correct fluid.

You can probably use your 80-90 gear oil for your front axle, depending on what's called for...

Post back results from the outcome.

 

[mercdv]

If it were me, I'd change the fluid twice more. I'd change it once and run it with a new filter and any attachments on the machine that were put on during the period of the wrong oil being used. Get it all warmed up and then change the fluid again and the filter. I'd at least drain half of it again at the bare minimum after the initial complete change. You really want to flush out as much of the 80W-90 as possible. The extra fluids are gonna cost a bit but that's better than having to buy a new pump and parts, not to mention the time required to switch out the pump. Just something to think about....

 

[sconnie]

Thanks all for the additional information. I will try to be more cognizant of paragraph structure going forward.

I finished changing the fluid yesterday. I drained the the entire reservoir tank, removed the screw on filter, and removed the mesh screen filter way at the bottom of the reservoir tank. A note to anyone who's draining out the hydraulic fluid on this machine: removing the screen filter at the bottom is crucial for removing as much of the fluid as you can. I thought I had drained the majority of the fluid through the three drain bolts, but once i took out the screen mesh filter I'd estimate another quart of fluid came pouring out.

Once i removed the three drain bolts, the screw on filter, and the screen mesh filter, I started dumping the new AW46 hydro fluid into the system through the checking plug on top of the transmission housing (between your feet when sitting on the tractor). I poured ~2-3 quarts and then observed the fluid run out through the still open drain plugs. Once I saw the color running out change from pink/red (the 80w-90 was red) to clear (the new AW46 is clear) I screwed on the drain plugs, screen mesh filter and a NEW hydraulic filter (I bought a hydraulic filter from NAPA that was the equivalent, NAPA Gold 1663) I filled the reservoir up to "FULL" based on the dipstick and started her up.

To my disappointment, albeit naive in hindsight, the buzzing was still present although much more faint. I ran all the hydraulics throughout their full range of motion a couple times. I then actually ended up doing what you are suggesting merdv. I took all the drain plugs out again and removed the screen mesh filter and let it drain out again. It was clear that some 80w-90 had contaminated the AW46 as the fluid that drained out this time was not fully red, but also definitely not clear. One additional thing I tried on this round of draining was turning the tractor on for a couple seconds and working the loader levers. My thought was that this could help fully drain the hoses of the contaminated fluid. I may be informed that this was incorrect, but it did work in accomplishing my goal. I only did this for a total of maybe 10 seconds and then turned the tractor off and looked at the fluid draining below. Their was additional fluid that was streaming out of the drain plugs.

I then dumped a few more quarts of AW46 into the system and let it drain. At this point, the fluid draining out was nearly clear. I reinstalled the drainplugs and the screen mesh filter and filled the system up with AW46. I started up the tractor and the buzzing is nearly gone. I worked the hydraulics and took it for a spin around the property. There is still a buzzing sound relating to the clutch position as before but extremely faint. The swap to AW46 has helped the sound greatly. I drained out maybe a cup of the fluid to check. The fluid was not perfectly clear as it is in the bucket from the store but had an extremely slight pink tinge to it, I thought to an acceptable degree. The one thing I did not do and am debating if i should: after draining the first fill of AW46 that became pink and contaminated, i did not change the hydraulic filter again. Do you think that it would be beneficial to change the filter out one more time?

Something else i noticed in the cup of hydro fluid I drained out was there seem to be very small bubbles suspended in the fluid. Is this cause for concern? I've read that a small amount of bubbles is expected since the fluid is exposed to air in the reservoir tank but it should not be "foamy". I forgot to take a picture of this, I most likely will not be able to the next couple days but once I do I will post a picture to give an idea of the number of bubbles.

Overall I'm happy the fluid swap has seemed to greatly reduce the buzzing. It hasn't completely eliminated it, but I'm not sure how much should be expected. I know hydraulic whine is something guys on here mention so maybe the amount of buzzing i'm hearing at this point is regular hydraulic system sound? Additionally, I found some very fine metal flakes in the drained hydro fluid (picture attached). From what I read on other related forums, as long as there is no large chunks, this can be expected from he constant metal on metal movements?

Thanks again for the info everyone. Really appreciate it.

original buzzing sound
Mitsubishi MT18HD Hydraulic Buzzing - YouTube

buzzing sound with correct AW46
Mitsubishi MT180HD - Post Hydraulic Oil Change - YouTube

Metal flakes in drained hydro fluid

 

[Fallon]

Bubbles are bad & usually indicate an air leak. Generally the only place that can happen is the suction lines between the tank & pump.

Air (like to thick of fluid) causes cavitation. Cavitation is when a pump pulled a vacuum. This generally happens at the operating parts. The fluid gets pulled apart & microscopic bubbles form. When the vacuum is removed (part way through the pump) they violently collapse causing tiny shockwaves that can erode tiny bits of metal. Over time things start to look pitted & sandblasted. Not good for precision parts that need to be within a thousands of an inch & perfectly smooth to seal & operate right. Air just causes the process to accelerate as there are already bubbles to grow & collapse.

Cavitation & making sure there are no inlet restrictions is why hydraulic filters are usually on the return lines not the suction line. Cavitation from intake restrictions will kill a pump faster than lightly contaminated hydraulic fluid.