Hydraulic Leak from HST Case CK30 / CT230

[ss4010]

Hi All,

I have a 2009 Bobcat CT230 (White paint version of a Kioti CK30 HST) which looks to have developed a leak from inside the HST case.

Background:

Tractor is at the 500 hour service mark. It's had the HST pedal "sticking" for a number of years though occasional / minimal. I noticed the trans fluid was at the low limit, so I added about 1 gallon of fluid bringing it up to just below the full line on the transmission. After running it for about an hour, I noticed oil drops on the driveway. No apparent loss in performance. Power seems good though I suppose it could be gradually decreasing over 10 years and I just did not notice. After checking the level it's down to just below the min line on the dipstick.

After investigation (involving removal of a section of my homemade backhoe subframe) the leak was determined to be coming from the large ~75mm hole in the bottom of the HST Case.
Discovered inside was a rats nest. It seems like the entire case was filled with sticks, acorns, scrap paper, chewed up rubber gloves, leaves, and other rodent treasures. I flushed it out with a garden hose and about a gallon of debris washed out.

Getting on to the questions, hopefully someone here has taken one of these apart and can provide insight.

1. Is there anything inside the HST case that can be chewed by vermin (and cause a leak)?
2. Are there any relief valves or vents in the HST case? (attached image with arrow points to a possible RV?)
3. It seems possible there might be a leak at one of the propeller shaft seals or return lines going into the middle case?
4. Its due for service anyway, could a partially clogged HST filter result in back pressure and leakage inside the HST assembly?

Before everyone chimes in about calling the dealer, they dropped Bobcat about 7 years ago and were never really seemed interested in tractor sales in the first place.

Clearly I'm dreading the possibility of splitting the tractor just to investigate. So I'd like to do a little research up front.


I'll add pictures in the next post.


Thanks,


Steve

 

[ss4010]

Adding pictures of Debris and location of oil leak...

 

[justman777]

I think you're on the right path with a leaking seal. I don't think there's anything a rat/mouse/varmit could chew inside the HST that would cause a fluid leak. But, I've been wrong before! Most vents I've seen have been towards the top of the HST sump where they have less of a possibility of getting dirt in the fluid.

If you have a plumber friend, you may be able to get one of those camera scope things and poke it up in there to see where the fluid is coming from. It may be coming from somewhere else and just dripping down in there.

 

[ss4010]

I think you're on the right path with a leaking seal. I don't think there's anything a rat/mouse/varmit could chew inside the HST that would cause a fluid leak. But, I've been wrong before! Most vents I've seen have been towards the top of the HST sump where they have less of a possibility of getting dirt in the fluid.

If you have a plumber friend, you may be able to get one of those camera scope things and poke it up in there to see where the fluid is coming from. It may be coming from somewhere else and just dripping down in there.

Great idea. I picked up a endoscope on Amazon for $40.

I was able to take a few quick pictures up inside the HST case. As it was getting dark and the bugs were chewing pretty bad, only a few shots were taken.

Attached you will see what looks like a leak around the tube that seals the drive shaft for the front wheels? Ironically I don't see any seals in the shop manual / breakdown? Further up in the area around the HST pump seems to be dry. I'd estimate the leak rate to be 1 gallon for every 2 hours running. I'll look to get more photos and will likely add some oil to the trans and fire up the machine while monitoring.

Attachments
1. Above tube with 4wd shaft and to the port side of tractor. Seems dry.
2. Way up, near the deck. Also seems oil free.
3. The suspect area? Lots of oil here. This is what appears to be the tube containing the shaft for the front wheel drive.

 

[dfkrug]

2. Are there any relief valves or vents in the HST case? (attached image with arrow points to a possible RV?)
View attachment 655239

Sorry to hear of your rat attack. Wood rats (packrats) are a big problem here, too.

I also bought a new CT230, back in 2010, prob from the same dealer you did (Salinas). I still have the CK30 I bought new back in 2005.

Your drawing does indicate one of the 2 RVs in the case, for the Forward and Reverse HST circuits. It does not help with your leak, however. I have removed and inspected these RVs on my CK30.

 

[justman777]

If it's the oil seal for the shaft, they're generally not that expensive. I had to replace the front transfer case oil seal twice on my JD2305. Unfortunately, they can be a bear to get out even with the "right" tools. I think I wound up drilling into the seal and putting two wood screws into it to get some leverage to pull it out. You have to be careful though to not drill into the sealing surface or the gears behind the seal. You just want a hole in the metal surface to get your screws into.

Not a fun job at all, and you have to drop the shaft on one end or the other to get to the seal.

 

[ss4010]

It's time to update this thread.

Well after lots of disassembly of the tractor, it appears the root of the leak issue has been found.

Appears to be a failed gasket in the HST motor (section at the bottom of the tractor, just above the propeller shaft for 4WD). The HST unit as three sections. Precharge pump, motor and swash plate.

Trouble is nearly the entire tractor requires disassembly to get there. It should be noted the several of the fasteners near the top, just under the drivers seat between the mid case (section in between the HST and transmission) were found to be quite loose. My first thought was they were stretched from use of the loader and backhoe. Pulling them and measuring them did not indicate any stretch. Aside from the paint on everything after assembly, there did appear to be some loctite (grey?) on the threads.

While draining the hydraulic fluid a couple of pieces of case sealant (silicon rubber) was found inside the large grey filter. One piece was roughly 8" long. The running theory at that point was a section of gasket was sucked in and was the source of the leak. Given the seals exposed to hydraulic fluid were in and around the transmission case (mid case, PTO and 3 pt lift / MLS). The Kioti manual suggests the sealant is ThreeBond 1206D, which only appears to be available on Alibaba and likely out of production. I tried to message the US support office in LA a few weeks age to find the current replacement with no response to date,

So the journey begins. The tractor was split at the clutch. The firewall (steering and electrical lifted off), the clutch housing removed and finally the HST case. To do this pretty much every hydraulic line, fitting. mechanical linkage and electrical connection was removed. So far the only losses have been 1 spring (hst pedal switch) bent, on cir clip lost, one spring pin lost and one shaft pin lost.

Pictures with comments to follow. Also if anyone wants a specific picture of any of the parts let me know, as the tractor is pretty much in little pieces right now.

 

[ss4010]

Just adding some pictures. One is of the tractor (mostly together) just in case the patient does not survive surgery. Another is with an endoscope, jambed up inside the HST case, noticing the drip, which is evident even when the engine is off.

Also is an example of a loose fastener as found, along the top of the mid case. 4 bolts were found to be loose in varying degrees with this one being the worst example.

 

[dfkrug]

Very interesting. I hope to see some pix, esp of anything related to the HST.

Was there any sludge in the bottom of your sump?

No need to use the same sealant that DaeDong used back in Korea. Plenty of alternatives here.

How long before this is back together? Maybe I can come see while it is apart?

 

[ss4010]

As it was necessary to drain the case anyway, I went ahead and pulled the filters. Note the big piece of gasket material caught in the filter. New filters are shown (with part numbers) for reference.