B7100 HST hydraulic oil leak

[Whit]

I have only owned this tractor for about a month so still figuring it out.
After using the tractor for about 1 hour today, I noticed there was a slow oil leak dripping on the ground under the hydrostatic transmission. I can't exactly tell where it is coming from though. It seems to be where the hydraulic transmission is joined to the rear diff?
It is on both the left and right side of the clutch housing which encases the HST by the looks of things? It is hard to actually see the HST inside the clutch housing.

Oil leak right side

Oil Leak left side

The only thing I could find was a crack around this bolt at the top. Not sure if that is causing the leak though.

The HST and clutch hosing was a bit warm, I am not sure if that is normal?
The only other thing I can think of is the front drive shaft wobbling is somehow causing the HST to leak. I posted about the front drive shaft here.

Does anyone know where the leak would be coming from or how I can investigate further?

 

[TheOldHokie]

I have only owned this tractor for about a month so still figuring it out.
After using the tractor for about 1 hour today, I noticed there was a slow oil leak dripping on the ground under the hydrostatic transmission. I can't exactly tell where it is coming from though. It seems to be where the hydraulic transmission is joined to the rear diff?
It is on both the left and right side of the clutch housing which encases the HST by the looks of things? It is hard to actually see the HST inside the clutch housing.

Oil leak right side
View attachment 86864

Oil Leak left side
View attachment 86865

The only thing I could find was a crack around this bolt at the top. Not sure if that is causing the leak though.
View attachment 86870

The HST and clutch hosing was a bit warm, I am not sure if that is normal?
The only other thing I can think of is the front drive shaft wobbling is somehow causing the HST to leak. I posted about the front drive shaft here.

Does anyone know where the leak would be coming from or how I can investigate further?

Its a 40 year old tractor so small leaks are pretty common. Unless its leaking significant volumes live with it. Fixing the leak will require splitting the tractor = significant time and money.

I would be more concerned with the crack in the case flange. If that spreads the cost of repairs goes up.

Dan

 

[DustyRusty]

That crack is on a hanger bracket, and it can be removed and the crack welded and ground smooth. They will V out the crack and then fill it with weld it. It shouldn't be causing any leaks. If necessary, you can add some ultraviolet dye to the oil to find the source of the leak.

 

[Kenonf]

I read your problem about the front drive shaft wobble and then saw this post and noticed your reference to it. Unfortunately it is possible that the wobbly drive shaft is causing an oil seal failure, flexing the shaft that runs thru the HST.
does it drip while the engine is running with everything in neutral and the clutch in, or does it leak the same amount?
There are some pressure seal o-rings that may have just gotten old/dried out from sitting.
Wash down with light solvent(paint thinner or stronger) brush out debris, and blow out around the hst. Stuff some paper towel in the holes ands see what gets oil on it first.
Splitting is inevitable, if you want to fix leak.

It is now the tough choice you need to make, do I throw more parts and money at it or do I keep limping along till something else breaks. You can expect that the bearings on the front drive shaft and HST are under additional stress from the bent shaft.
Just do not let the HST run low on oil, it will kill it in seconds.

Here in sunny 37.7C Florida the HST and tractor get very while running

 

[Whit]

That crack is on a hanger bracket, and it can be removed and the crack welded and ground smooth. They will V out the crack and then fill it with weld it. It shouldn't be causing any leaks. If necessary, you can add some ultraviolet dye to the oil to find the source of the leak.

Thanks for the help, I am just wondering can that bracket bit be removed without splitting the tractor completely there? It looks like it is welded to the tunnel case bit and I could just remove the bolt and grind out the v from the front as you said?

 

[Whit]

I read your problem about the front drive shaft wobble and then saw this post and noticed your reference to it. Unfortunately it is possible that the wobbly drive shaft is causing an oil seal failure, flexing the shaft that runs thru the HST.
does it drip while the engine is running with everything in neutral and the clutch in, or does it leak the same amount?
There are some pressure seal o-rings that may have just gotten old/dried out from sitting.
Wash down with light solvent(paint thinner or stronger) brush out debris, and blow out around the hst. Stuff some paper towel in the holes ands see what gets oil on it first.
Splitting is inevitable, if you want to fix leak.

It is now the tough choice you need to make, do I throw more parts and money at it or do I keep limping along till something else breaks. You can expect that the bearings on the front drive shaft and HST are under additional stress from the bent shaft.
Just do not let the HST run low on oil, it will kill it in seconds.

Here in sunny 37.7C Florida the HST and tractor get very while running

Thanks for your help, I will do as you suggested with stuffing the paper towels down there. When I first got it after washing/degreasing I mowed for about 2 hours and didn't notice any oil leaks. it was only after using it again trying to test the diff lock (I have another post about the diff lock) that I noticed the oil leaking and it was very warm. I need to do some more testing. As the oil on the dipstick doesn't seem to go down, so it is not like it is sitting there leaking oil.

The only other thing I was wondering if there is too much hydraulic oil? and it is expanding when it gets hot with no where to go?
This pic is of the hydro oil dip stick level. It is all the way to the start of the round part of the dip stick. Where is it supposed to be? as the manual isn't clear to me.

 

[Kenonf]

From the other post, the oil is leaking from the bolt looking things on the bottom of the hst, there is a roll pin through the head of the bolts that holds a cap, o-ring and spring in there I believe is is a pressure relief of some kind. I believe the previous owner may have toyed with the hst for more speed. Look closely at the pictures.
A little oil drop looks like a huge leak usually, even though it is a small leak. Any kind of grass and or dirt will hold the oil and make it hard to determine the leak, need to be almost spotless to get a good read. Oil will climb uphill on dust and dirt

My leak has not gone away, but is significantly smaller than it was. at some point I will get correct fittings for my gauges and read pressures on the HST. Just load it on the trailer and go the the hydraulic supply and fit them in the lot.

If you over fill the hst it will come out of dip stick hole, I know that from experience.
As far as level I think it is a check cold style... cold level is to the line, and stick is wet all over when hot.

 

[Kenonf]

Looking back at the pictures too, make sure you are using a good(Kubota UDT)hydraulic tractor oil, not sure what previous owner had in mine, but it looks very dark in the picture.

 

[Whit]

I have drained the hydraulic fluid and pulled the rear right axle case off to investigate the diff lock not working. I posted about it in this thread.
B7100 HST Diff lock does not seem to be working

There was some sludge in the bottom of the case corners so I am guessing there is more through the hydraulic system. Any ideas how to clean the system?

This is the oil that came out. Is it normal?

I have bought Kubota UDT oil and new filter so will refill with that and monitor leak.

My HST pedal does not fully return to neutral from forward and reverse so the tractor creeps in either direction until you get the pedal in the right spot. Would that have anything to do with the pressure relief or oil leak?

 

[Kenonf]

Well that's pretty oil. A little moisture problem in there too, No it is not normal. You might just want to fill it up with UDT, run it for an hour and do another change... might help leaks and the sludge...going to be expensive but if the HST is strong it will be fine.

The HST filter is there on top of the HST, you will need to change it.
There are also suction screens on the sides of the tractor that need cleaning,.

The dealer here told me the way they test the hst is they move the tractor nose against a tree and push on the tree with the pedal, if the rpm drops then the HST is OK, if the tractor does not drag the motor your hst is shot.

The HST pedal sticking is a different problem, There is a plate on the HST pedal side of the tractor. The pivot mechanism is back there, there is a ring and a bearing that you will need to look at... or in your case the ring might be gone. there are a few more in depth threads about it on the forum so I wont rehash them. Just search "b7100 hst pedal sticking".

If you can get by without the dif-lock working you might want to wait and put a few more hours on the tractor and see what other problems you might have. The machine looks like it was not well maintained, and would hate to see you spend more money when the hst only has days on it, or the headgasket is shot and previous owner put sealant into the radiator, to stop it from leaking while he sold it.

I have had to get radiator re-cored here locally for $400 on one of my B7100s, because it kept overheating.

Try and find a donor unit, you seem mechanically inclined and it will provide east access to parts.

Ken

 

[Whit]

Well that's pretty oil. A little moisture problem in there too, No it is not normal. You might just want to fill it up with UDT, run it for an hour and do another change... might help leaks and the sludge...going to be expensive but if the HST is strong it will be fine.

The HST filter is there on top of the HST, you will need to change it.
There are also suction screens on the sides of the tractor that need cleaning,.

The dealer here told me the way they test the hst is they move the tractor nose against a tree and push on the tree with the pedal, if the rpm drops then the HST is OK, if the tractor does not drag the motor your hst is shot.

The HST pedal sticking is a different problem, There is a plate on the HST pedal side of the tractor. The pivot mechanism is back there, there is a ring and a bearing that you will need to look at... or in your case the ring might be gone. there are a few more in depth threads about it on the forum so I wont rehash them. Just search "b7100 hst pedal sticking".

If you can get by without the dif-lock working you might want to wait and put a few more hours on the tractor and see what other problems you might have. The machine looks like it was not well maintained, and would hate to see you spend more money when the hst only has days on it, or the headgasket is shot and previous owner put sealant into the radiator, to stop it from leaking while he sold it.

I have had to get radiator re-cored here locally for $400 on one of my B7100s, because it kept overheating.

Try and find a donor unit, you seem mechanically inclined and it will provide east access to parts.

Ken

Thanks for all this information it is really helpful! I am a little mechanically inclined but also learning lots thanks to this forum.
That is the what I am trying to figure out how much of the tractor is working vs how much money to put into it as you said the machine was not well maintained.

I did a full service on the weekend, replaced all fluids and filters. There wasn't even a fuel filter in there to replace!!! So now it at least has a new one. I will do as you suggest run it for a bit and replace the HST filter.

I did try what you suggested to test the HST however I just get wheel spin, so I don't think there is a chance to fully load the HST? Is there a way to do it without getting wheel spin?

I think I may have figured the diff lock issue out. Which I posted an updated about here
B7100 HST Diff lock does not seem to be working

I started a new thread about my creep issue. I read through some previous threads but couldn't find any answers.

B7100 HST forward and reverse creep

My B7100 Creeps the same amount in forward and reverse. The only way to get it to stop creeping is to keep taping forward and reverse slightly until it stops creeping. I marked position of neutral adjuster. Adjusted as per manual turning it clock wise and anti clockwise etc. Ended up in the...

www.orangetractortalks.com

When you mention ring? Is that the bushing where the neutral arm attaches to the HST?

Back to the leaking I had a good look underneath the tractor and all I could really see is there is teflon tape around the 2 neutral valve bolts at the bottom of the HST, so maybe the O rings have failed and someone tried to fix with tape?
However there is also oil up higher so I am wondering if the pressure relief valves O rings have also failed?because previously I would hear it hissing/leaking after using for a few hours. and if there was a lot of water in the oil maybe it was boiling causing more pressure build up?

I need have another look now I have changed the HST oil and filter.

 

[TheOldHokie]

Thanks for all this information it is really helpful! I am a little mechanically inclined but also learning lots thanks to this forum.
That is the what I am trying to figure out how much of the tractor is working vs how much money to put into it as you said the machine was not well maintained.

I did a full service on the weekend, replaced all fluids and filters. There wasn't even a fuel filter in there to replace!!! So now it at least has a new one. I will do as you suggest run it for a bit and replace the HST filter.

I did try what you suggested to test the HST however I just get wheel spin, so I don't think there is a chance to fully load the HST? Is there a way to do it without getting wheel spin?

I think I may have figured the diff lock issue out. Which I posted an updated about here
B7100 HST Diff lock does not seem to be working

I started a new thread about my creep issue. I read through some previous threads but couldn't find any answers.

B7100 HST forward and reverse creep

My B7100 Creeps the same amount in forward and reverse. The only way to get it to stop creeping is to keep taping forward and reverse slightly until it stops creeping. I marked position of neutral adjuster. Adjusted as per manual turning it clock wise and anti clockwise etc. Ended up in the...

www.orangetractortalks.com

When you mention ring? Is that the bushing where the neutral arm attaches to the HST?

Back to the leaking I had a good look underneath the tractor and all I could really see is there is teflon tape around the 2 neutral valve bolts at the bottom of the HST, so maybe the O rings have failed and someone tried to fix with tape?
However there is also oil up higher so I am wondering if the pressure relief valves O rings have also failed?because previously I would hear it hissing/leaking after using for a few hours. and if there was a lot of water in the oil maybe it was boiling causing more pressure build up?

I need have another look now I have changed the HST oil and filter.

View attachment 88603

View attachment 88607

If it spins the wheels its got more power than it can put on the ground. That is not an HST problem.

Dan

 

[Kenonf]

Those pics are perfect!
Agreed on the wheels spinning, your hst is fine, just leaking.
Go here Kubotabooks.com and download the service manual.
My leak was from the recess in those bolts, that is where I replaced the o-rings, there was a roll pin that held a steel plate in the bolt and an o ring behind it.
You replied to my original post, I have not really done anything else with it, I believe it is leaking even less now. The hiss could be from steam escaping... Thinking back, oil could be leaking from any number of shaft seals on the HST. I would continue to run it and watch oil levels and see where you are after 6 months. splitting it is not hard but it does take some time and floor space, and that is about the only way to fix it all, is to just start replacing all the seals between HST and the tunnel.

In the HST pedal picture, the bearing rolls on the plate that you pivot by pushing on the pedals. that plate also is attached to the HST to drive direction and speed. The bearing pushes the plate back to a neutral position, when you remove your foot or change pressure you are putting on the pedal.
One end of the bearing holder attached to a spring, the other has a ring welded on it. the ring has a plastic slip ring inside of it that allows the entire bearing holder to pivot on another metal piece. The other metal piece is the neutral adjustment device. It is an eccentric piece that is held in place by a bolt you can see from the outside of the tractor thru the hole you can see in your picture. Loosing the bolt allows you to adjust the neutral position of your pedal.

That is the parts description part. now the fixes, you can tighten the spring that is attached to the arm and comes up thru the tractor body by the filter. The roller bearing might be worn out or stuck. And or the plastic ring that the arm pivots on might be sticking, broken or gone. The eccentric piece might need to be rotated to get the pedal into the correct position. All of those things can effect the HST pedal movement or lack of movement. I have had the ring gone problem and oil swelled the plastic ring so it would not move freely. A new plastic ring fixed both problems.. I went ahead and tightened up the spring on the arm, on both b7100s.
Ken