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.