B2410 HST Fill Plug... Why Did It Depart?

[NoJacketRequired]

OK, folks, I'm the guy who always talks about how my Kubota B-series tractors work their hearts out and are more reliable than rain in the rainforest. Well, today I received a bit of a surprise.

I've been using my B2410 for snowblowing using the front-mounted B2550C blower. There's a fair bit of "backing and forthing" in this work as I'm clearing a square-ish area rather than working on a long driveway. The tractor performs flawlessly and, frankly, is an absolute pleasure to operate.

Imagine my surprise when I discovered this morning a great gaping hole where the yellow plastic HST filler plug used to be! I noticed it because I also noticed a light film of oil on the back side of the seat back and on the under-seat tool box.

Previously on a couple of occasions I had found the plug having drifted upwards out of its hole and sitting a little bit askew. Thinking nothing of it I simply pushed the plug back down to its fully seated position and got working again. The plug didn't seem to fit very tightly so it didn't surprise me that it had moved from its fully-seated position. This time it seems the plug came right out and disappeared somewhere in the snow.

Question for the Kubota cognoscenti:
Is there any other reason why this plug would exit the tractor, a reason other than just old age and having shrunk a little over time? Is there perhaps an HST vent line which might be blocked, allowing pressure to build up in the HST as the oil warms under work load? If so, where would I find this little rascal so I can get it unplugged and breathing freely again?

Now I'm left wondering if the missing plug is still available through Kubota as a replacement part...

Thanks to all for your helpful replies.

 

[North Idaho Wolfman]

There is a ? mark vent hose just to the right front of plug location make sure it's clear.
Was the O-ring on the plug and yea that style of plug has been found to deform / over time.

 

[D2Cat]

Like North Idaho Wolfman suggested, something is causing pressure to build up. Maybe a mud dobbers nest in that J hook vent.

 

[whitetiger]

Here is the parts breakdown with the parts numbers for the plug #190 and O-ring #200.
Also, pictured is #180 which is the trans-axle vent you asked about.

 

[Henro]

I once had a similar experience with my B2910. Knowing my weaknesses, I just accepted the fact that I forgot to put the plug back in after the last time I added some fluid. Fortunately I found the cap on the back of the tractor somewhere...probably because I have a heavy duty top link installed that contained it.

Any chance you may share the same weaknesses that I know I have?

 

[number two]

My B3030 has the same yellow dipstick on the front axle.
The vent is right next to it.
Mine fits harder than the hubs of hell!
I use a couple pocket screwdrivers to remove it
I lube it when installing still have to wack it with a soft mallet.
Good Luck!

 

[NoJacketRequired]

Many thanks for the excellent help, folks!

NIW - the rubber o-ring gasket may have disappeared and that may have been the original root cause. No matter, the whole thing is gone now.

Whitetiger - thanks for the parts list, that's very helpful.

Yup, I'll double-check the J-hook vent line as it could very well have become clogged.

Henro - to answer your question, on the day the plug departed I had very consciously re-seated it at the beginning of the snow blowing session so I knew it was indeed in place when I started. My background is in aerospace and I build, own and fly airplanes so my "walk around" checks on tractors are done with the same rigor as I do them on airplanes. yes, I'm human and DO make mistakes, sometimes real doozies, but this is one instance when I have a high level of certainty that human error didn't come into play.

Now I'll check with the local dealer to see if I can get a new plug...

Again, thanks to all for your very helpful responses. This is such a great gang!

 

[Russell King]

Can you attach the plug to the tractor with a chain so if it falls out it will be hanging on by the chain? Is there a tab to drill a hole through?

this kind of chain is what I mean…

 

[GreensvilleJay]

yeah, use THAT chain and you'll wonder WHERE the heck did the bathtub plug go ??????

 

[nbryan]

I kept a plastic juice crate with supplies for chainsawing etc on top of the 3-point upper lift arms when I shuttle the trailer and tools out to the cutting area, until once I lowered then lifted back up the 3-point a bit with the crate on there.

I then got home and noticed the cap had been stripped out of the hydraulic fill hole by the box sliding against it and getting pushed by the 3-point lift action.

I bunched up a plastic bag tightly and temp plugged the hole. Got a new one the next week.

 

[NoJacketRequired]

New plug and o-ring are on order with the local dealer. No ETA yet... In the meantime a thorough inspection of the ?-shaped vent tube will take place.

Isn't it amazing the places insects find to build their nests? In the airplane world mud daubers are famous for filling fuel tank vents. It's a bit scary to look out the window and see the skin of the wing sucking inward as the engine is trying to pull fuel from the tanks! (Been there, done that, exactly once! Now I carry a piece of stainless steel safety wire in my flight bag to poke out the dirt that insects might leave.

For those who have troubles with mud daubers filling up and plugging vent lines, a good fix is old fashioned pipe cleaners stuck in the vent. The "fuzz" of the pipe cleaner discourages the mud daubers while also letting air flow past.