Loosing hydraulic oil from the vent

[CurtisC]

My 2009 B26TLB has 658 HRs on it. It received its 600 HR maintenance on schedule including replacing the the hydraulic and HST oil filters with WIX as well as new oil which has always been Kubota Super UDT. After noticing performance problems and whining issues around 610-620 hrs. I changed the WIX filters out for Kubota and all was good again until recently. Around 650 hrs the vent by the fill plug started leaking oil while working the tractor fairly hard regrading gravel on on a lengthy steep driveway. The naturally whiney HST transmission had also changed its tune (hard to describe but a more full throated whine). When I checked oil level it was high (after pulling dip stick then reinserting to get the reading). I drained some oil, got a good reading and hoped it was my mistake in overfilling the tank. Checked it several days later - it was low. Added oil and hoped for the best but knew something was up. Today after another minor work out, more oil coming from the vent plus the transmission continued not to sound like its usual self. Checked oil after back on level ground and I was down to the add line - not sure if that's a full qt. or not but its close.
For those of you more up on hydraulic HST systems than I - any idea what's up? After being bit by WIX filters I'm suspicious of the HST filter, although now OEM, is there some way it can fail, starve the transmission and force oil out the vent? Sorry for detailed story but thought it might be helpful.

 

[Dave M7040]

From memory there is a new improved suction line.

Suction line problems tend to aerate the fluid resulting in fluctuating oil levels and changes in sound.

Look at post #5 in the thread linked below.

B26

Dave M7040

 

[Smokeydog]

I suspect cracks in the suction line line elbow. The link above details the replacement and new and improved line assembly. Achilles’s heel of an otherwise tough machine. Might consider changing the hst filter if replacing the suction line.

There are drain plugs on either side of the rear axle detailed in the owners manual to remove when draining the hst oil. The picture in the manual shows the plug without all the framing for the loader/backhoe installed. Got very little oil out of those and are very difficult to access to R&R. Noted no debris in oil from those drain ports but hard to see. I might consider doing those every other oil change.

Expensive machine and oil. I would use Kubota filters for piece of mind. The hst filter is replaced every 200 hours with little loss of fluid.

 

[CurtisC]

Thanks Dave, Smokeydog, not sure why I wasn't thinking aeration as the cause. I did replace the rubber elbow with an "improved" elbow due to the potential for cracking around 400 hrs. I was chasing a severe cold weather performance and noise problem after the servicing which finally disappeared after chucking the WIX hydraulic filters and going back to OEM. At the time I don't think Kubota had decided to revamp the whole suction run, at least the they didn't mention it when suggesting the elbow R&R.
Due to other commitments it will be a while but I will replace the whole run and post results.
Thanks again!

 

[woody]

when I had that problem it turned out to be a seal in the pump, the elbow was replaced first but did not fix the problem.

 

[CurtisC]

Given Kubota took the time to re-engineer the whole suction line, sounds like the smart place to start, leak or no leak, however going through the pump will be plan B. Did you tear it down or have dealer or HYD shop do it?
Thanks, Greg

 

[CurtisC]

Update. Just finished replacing the suction line with kit from Kubota. I thought I was buying just the elbow (as did the parts guy) but got the whole kit which went from one long convoluted metal line with an elbow at the pump to a shorter metal line, a short section of hose, a metal 90 bend, the rubber elbow to the pump, and a bunch of band clamps. Turns out the old rubber elbow did have multiple cracks on the engine side that were not visible. Clearly Kubota knows they have a vibration stress issue with the old design as the price for the kit was less than $40 - about what I paid for just the elbow several years ago.
Some suggestions for anyone attempting the repair;

1. Take the wheel off to get little better access to the bolt holding the metal line to the tank (couldn't brake the bolts on mine so it stayed on)
2. Jack the right side up with right B/H stabilizer (and block it) to get better access below and it raises the line connection at tank to mitigate fluid loss.
3. Oil up and install the o-ring and cap or bag both ends of the new metal line to keep out debris. Also clean off the area around the tank connection.
4. Lay in the new metal line next to the old coming in from the rear.
5. Disconnect old line at the elbow - have a catch pan for oil coming from pump
6. Metal line retaining bolt at the tank is very tough to get to - I used 12 pt. box wrench and was able to get about an 1/12th of a turn at a time.
7. Position a catch pan under the tank connection and get the new line ready to insert in place as soon as you pull the old out. Be aware the old line is still full of oil so keep the end over catch pan to drain while inserting the new line. With the tractor jacked up oil did not make it up to the other end of the line.
8. Oil up the connections on the rest of the parts up by the pump, install and achieve best alignment before clamping.
9. Have an extra gallon of SUDT on hand - I lost a little more than a 1/2 gallon.

Even if you're not having problems but have the old line configuration, I'd recommend the swap next time you change filters and fluid - much easier then!

 

[Smokeydog]

Hope the new line configuration is a durable solution to the rubber elbow cracking. Still probably replace again at the next 400hrs fluid change.

Could you tell any difference afterwards?

 

[CurtisC]

Started it with everything cool (not cold) sounded the same. Let it sit and run a bit first to send any trapped suction line air back to the tank, HST and all actuators worked fine. Below you can see the cracks in the old elbow and where they added (#35) a new rubber hose section in the kit. Besides added vibration dampening, the added hose gives you an opportunity to get everything aligned to relieve any mismatch from the old factory pipe and pump. Still need to give it a workout and make sure the pump wasn't also a contributor but otherwise all good.

 

[Dave M7040]

Curtis
Thanks for reporting back.

All too often people ask for help, get good advice which solves their problem and just disappear.

Feedback on suggestions helps many learn which is what the forum is about.

Dave M7040