BX Axle Breather

[bluedunn]

Hi-

I was out working this weekend, doing some loader work and noticed, after parking the tractor that there was a very tiny bit of axle fluid around the front axle joint on the left side of my BX.

I just (like a month ago) had the seals replaced on both sides because the front left was leaking pretty steadily. To say this (some fluid around the knuckle) was aggravating would be an understatement.

I next removed the dipstick to check the level and to my surprise it shot out like a champagne cork! I've done a search on this and it does seem to be a common issue; that pressure builds in the front axle housing and in some cases, causes fluid to seep past the seals and/or shoots the dipstick out.

So couple of questions; I haven't noticed any dripping or leaks near the front left seal since I removed the dipstick and wiped away what little fluid was there.
-Do you think I now have another leak at the left front axle?
-Would it be worthwhile to try and put a breather of some type on the front axle to avoid the pressure build?
-If I do put a breather on, I was thinking of replacing one of the existing breather bolts with something with an actual breather...if I do this does anyone know what kind of bolts these are (metric, pitch, etc)?

Thanks for any help!

 

[Dave_eng]

The "breather" plugs on each side of the front axle are there to vent any trapped air as the fluid is being added to the front axle assembly. Otherwise a trapped pocket of air would keep the fluid from filling the gear cases at each end of the axle.

Once their job is done during the oil fill, they become sealed plugs and have no further function.

I am always reluctant to alter the original design which does not include a vent tube which remains open to the atmosphere because none of us know the considerations the Kubota designers looked at in arriving at the final design. Often vents allow moisture in and cause as many problems as they solve. The volume of fluid in the front axle is quite small at 2.3 liters so volume change with temperature is minimal..

On front axles for larger tractors (which hold a lot more fluid) Kubota has incorporated a vent tube.

Dave

 

[bluedunn]

The "breather" plugs on each side of the front axle are there to vent any trapped air as the fluid is being added to the front axle assembly. Otherwise a trapped pocket of air would keep the fluid from filling the gear cases at each end of the axle.

Once their job is done during the oil fill, they become sealed plugs and have no further function.

I am always reluctant to alter the original design which does not include a vent tube which remains open to the atmosphere because none of us know the considerations the Kubota designers looked at in arriving at the final design. Often vents allow moisture in and cause as many problems as they solve. The volume of fluid in the front axle is quite small at 2.3 liters so volume change with temperature is minimal..

On front axles for larger tractors (which hold a lot more fluid) Kubota has incorporated a vent tube.

Dave

Fair point, and I've definitely mulled this over. Who am I to change Kubota's original engineering?

It makes me wonder if the Kubota folks intended for the front seals to seep though? Surely this is a sign that something is wrong?

I've checked the fluid level and it looks to be within the dipstick full range, so I don't think I've overfilled it. What makes me really concerned is that I just had the front seals replaced and now I'm seeing seeping, which is discouraging to say the least.

 

[dirtydeed]

What oil did you use when you changed the seals? If you used hydraulic oil (or super UDT) drain it, and replace it with 80-90W gear oil. That should slow down the seeps. Keep the level towards the bottom of the acceptable range for a bit to see if you still get leaks.

 

[bluedunn]

What oil did you use when you changed the seals? If you used hydraulic oil (or super UDT) drain it, and replace it with 80-90W gear oil. That should slow down the seeps. Keep the level towards the bottom of the acceptable range for a bit to see if you still get leaks.

I used 80-90W...I think. It was the Kubota brand from the dealer...so wonder if it may have not been what I thought it was. Last time I did changed the oil, I used Lucas 80-90W. Now I have to go look at the Kubota stuff the dealer gave me. The level is also near the higher end of the acceptable range, maybe draining out a little would help.

 

[Henro]

I have not had this issue with my BX, but the question that comes to mind is:

How can enough pressure build up in the front axle so the dipstick "shot out like a champagne cork!"

This puzzles me.

Perhaps those more knowledgeable can offer possible reasons.

Seems strange to me...also seems likely that the oil seepage is due to the pressure developing within the front axle.

 

[bluedunn]

I have not had this issue with my BX, but the question that comes to mind is:

How can enough pressure build up in the front axle so the dipstick "shot out like a champagne cork!"

This puzzles me.

Perhaps those more knowledgeable can offer possible reasons.

Seems strange to me...also seems likely that the oil seepage is due to the pressure developing within the front axle.

Puzzles me too, which is why I posted the original message; doesn't really seem like it should do that :-(

 

[BigG]

Here is one that does not cost much, and could be made to fit. Try it and if it works go for a better quality one.

I see you are in the NE so you could replug it in the winter to keep the moisture out in the winter.

https://www.classicindustries.com/p...hbSqGlMCS-1zi9OksoE2wesysSxBBAWhoCagAQAvD_BwE

I do not know what happen to the address so I will try again.

 

[countryboy9799]

I am not sure if this applies to the Kubota tractors but I think he is referring to a vent plug that vents air inside that builds pressure as it warms up. I know 4 wheelers have them on the transmission, rear and front end because the pressure will push the oil out. Pickup front and rear differentials have them also. I have had a few plug before and it is something you want to get fixed, hopefully someone knows if the Kubota's have them.

 

[bluedunn]

I am not sure if this applies to the Kubota tractors but I think he is referring to a vent plug that vents air inside that builds pressure as it warms up. I know 4 wheelers have them on the transmission, rear and front end because the pressure will push the oil out. Pickup front and rear differentials have them also. I have had a few plug before and it is something you want to get fixed, hopefully someone knows if the Kubota's have them.

Yep, that’s what I’m talking about. I think the larger Kubota’s have them, but not the BX ( I don’t think the B’s have them either).

 

[bluedunn]

I drained some of the oil to see if that might make a difference. The oil level now reads about 1/2 way between low and high on the dipstick.

 

[Russell King]

You may want to vent it when hot then reinstall the dipstick so as it cools it will pull a slight vacuum in the case. That way it may not build up so much pressure if it can hold the vacuum over time.


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[dirtydeed]

Yep, that’s what I’m talking about. I think the larger Kubota’s have them, but not the BX ( I don’t think the B’s have them either).

B's have them...or at least mine does.



I'd try fabbing something up with the vent plug on the other side. Since its threaded, maybe you can find some threaded fitting (like a reducer) to stick some tubing into it.

 

[Henro]

Just to carry the thought a little further.

Symptoms are oil leakage at a seal and apparently excessive pressure in the front axle housing.

Excessive pressure is likely forcing oil past the seal. I have always checked front axel oil level cold. Perhaps pressure when hot is normal. Next time I cut grass for a couple hours I will check mine immediately after finishing.

If excessive pressure is not normal, what would cause it? Heat causing the oil and air to expand probably. Is this normal, or is something wrong causing excessive friction somewhere and therefore excessive to be generated?

Is there any other way aside from heat that would cause pressure to build up?

Certainly adding a vent would eliminate the symptom.

But not the root cause of pressure developing within the closed space if this is abnormal.

Unfortunately all I have are questions and no answers.

 

[beex]

this is weird, I never heard of this much pressure building up.

My bx axle never gets hot that the expansion would be much. The axel can get warm from conductive heat from the engine, certainly not form internal generated heat from movement, the nothing moves very fast.

Maybe if you check the axel level in the lowest temp in the winter, equalize the pressure in sub zero, and don’t check it till a hot day in the summer you can get that much pressure?


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[bluedunn]

this is weird, I never heard of this much pressure building up.

My bx axle never gets hot that the expansion would be much. The axel can get warm from conductive heat from the engine, certainly not form internal generated heat from movement, the nothing moves very fast.

Maybe if you check the axel level in the lowest temp in the winter, equalize the pressure in sub zero, and don’t check it till a hot day in the summer you can get that much pressure?


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I wonder now if my front axle was just overfilled. Maybe enough so that whatever heat/pressure that was generated pushed a bit of oil past the seal...? So maybe it wasn’t excessive pressure but excessive gear oil. I have since drained some out (oil level is now half-way between low and full on the dipstick) but haven’t had a chance to run the tractor.

 

[bluedunn]

Hi-

A little more on this subject. I have not installed a breather, but did drain out a bit of axle fluid. I have noticed that the slight seep only seems to occur when I'm using the tractor, when it's parked and in the garage, not a drop is leaking. Does this seem odd? Does this confirm the fact that the pressure is building up and forcing fluid past the seal on the right-hand side? It's only the right-hand side that is the problem - the left-hand side is fine.

Since it's not leaking when it's parked, and only a small amount when in use, I'm wondering if I should just keep an eye on the fluid level and stop worrying about it. That said, it's one of those things that just bothers me.

Thanks for the continued help!

 

[ve9aa]

I have this exact issue with a brand new bx2380. (5.5hrs on it)
Front axle fairly warm, oil seepage @ right front breather bolt. (left is fine)
Plug shot out (almost) like a champagne cork.

 

[whitetiger]

I have this exact issue with a brand new bx2380. (5.5hrs on it)
Front axle fairly warm, oil seepage @ right front breather bolt. (left is fine)
Plug shot out (almost) like a champagne cork.

Are you referring to the vent plug on the top (14mm head)? If so, it has a sealing washer with a rubber insert under it. Check to see if it is tight, if it is, the washer needs replaced.

As far as the pressure, it is a non-vented assembly and when the oil is warm builds pressure. The dipstick will pop when removed, it's the nature of the beast.