Help diagnosing buzzing in hydraulics

[tehans]

I have recently noticed a buzzing in the hydraulic system of my tractor.. I realize the most likely causes are either cavitation or air entering the system. How do I troubleshoot/fix the problem?

It has a new filter and new fluid recommended by the manufacturer. These were done months before the buzzing presented itself. The tractor is a 90's era Kubota B2400 HSD with 800 hrs showing on the clock. Level of fluid is correct. Any help is appreciated

 

[Topzide]

Have you noticed any air bubbles on hydro dipstick? As far as what to check, start with the suction line clamps, then check all pressure line connections. I've had pressure lines work themselves loose from vibration and flexing with pressure from working them. Have you noticed any drops where its parked? Sometimes the clues are hard to see. Good luck.

 

[Dave M7040]

Posting exactly which tractor you have sometimes helps.

There are two HST models, a 2WD and a 4WD
Two manual transmission models, a 2wd and a 4WD

What have you done to try and localize the sound?

A length of rubber hose held in your ear and the other end at various places on the tractor can act like a cheap medical doctor's stethoscope

Dave M7040

 

[Tinhack]

Buzzing can also be caused by a pressure relief valve quick cycling due to a clog or restriction. Have you replaced any parts or hoses recently?

 

[tehans]

Buzzing can also be caused by a pressure relief valve quick cycling due to a clog or restriction. Have you replaced any parts or hoses recently?

I did replace a hose that had a small leak between the FEL control block and the rear of the tractor, but the buzzing was happening before I replaced it though.

HSD is the 4x4 hydrostatic model designation. I can feel the vibration/buzzing in all the lines, and power steering. So here is my initial plan, There is an S shaped piece of rubber tubing on the suction line that looks to be cracked and a little wet, planning to replace that, and take out the screen strainer (which is on the opposite end of that line) and clean/check it

 

[Leejohn]

I think you are heading just right.

 

[Smokeydog]

Sounds like a suction side air leak. Very often no external oil leakage. My B26 rubber elbow on the suction side had developed cracks before 400 hours.

 

[Texasmark]

I had more of a whine increasing than a buzzing. My hydraulic pumps are on the same shaft and fed with a letter F rubber adapter from the main hydraulic sump metal feed pipe. One day I noticed hyd oil in the vicinity and upon removal there were several cracks where the SS clamps attached the hose to the pump inlets. Changed the hose and things quieted down like new....yes hyd pump sucking air caused the noise. What I didn't realize too was the the FEL had been slowing down and now that it was back to OEM I noticed how much faster it responded.....seems you put a frog in a pan of hot water and it'll jump out.....Put it in a pan of cold water and turn the fire on and it will stay and cook. I guess I am a frog and was mesmerized........thought it was my premium hyd fluid failing me (the whine) after having changed it recently.

 

[Smokeydog]

Glad you found and fixed the problem. Seems to be a problem with newer kubotas. My old ones and other equipment didn’t have this problem. Sucking unfiltered air from down low into the hydraulic system is bad. I know I will be routinely replacing that rubber elbow from now on with the B26. To Kubota’s credit they did redesign the rubber and metal suction line to help maybe better fix the problem. My elbow is made without any fabric reinforcement.

On another post it was noted that radiator hoses are now experiencing shorter lifespans which are similar to hydraulic suction hoses.