Hydraulic Line Leaks: (Cracked Welds, Not O-Rings) for Bobcat CT-230 (or CT-235)

[DaveK OR]

I have edited the title of this post to reflect the fact that the leak resulted from cracked welds at hydraulic hard-line connectors. The original post continues below.

The hydraulic cooling line (the long one on the left side) on my CT-230 has suddenly developed a leak at its rear connection point. Having removed the line and cleaned it up, I can't find a crack in the weld at that connection so the most likely culprit is failure of the o-rings on that connection. Can anyone advise an Auto Shop (NAPA, for example) replacement for these o-rings? The Kioti parts diagrams show these as Number 04810-00200. These are higher durometer o-rings designed for high pressure, so I can't use the softer ones that are a lot more common.

It is still possible that the weld on that connection has cracked, but it's too small to see. I had that happen previously on a different line, and had to replace it. In that case you could see the hydraulic fluid spraying out under pressure from the crack, but it closed up invisibly tight when not under pressure.

I know I could get these o-rings from Bobcat, but that is a 60 mile trip, and there's a NAPA store just down the road.

 

[winston1]

Do you know what durometer are you looking for? I would buy these and try them? Harbor Freight Tools – Quality Tools at Discount Prices Since 1977

 

[DaveK OR]

An update on my problem.... it's not the o-rings!

I was able to locate replacement o-rings (and the ones from HF are way too soft for this service), installed them, and tightened all the fittings. When I fired up the tractor, I still had the leak!

Since everything was now clean, I had a good look at the connection, and it was pretty apparent that there was a crack in the weld that connects the hydraulic tube to the double o-ring connecting boss. Because there was a little air in the system from disconnecting that hydraulic line, you could occasionally see some tiny bubbles appearing along the crack.

It's too bad that my tractor has 400 hrs and 10 years on it, because this is pretty clearly a design flaw (probably Kioti's fault, not Bobcat). I'm willing to bet that when I get the replacement line, that connection will have a slightly different construction and weld design to prevent that kind of stress cracking.

I considered trying to silver-solder the crack, but it is so very tiny that you simply cannot see it until it leaks under system pressure. I doubt you could even clean the joint, let alone get silver solder to reliably flow into such a tiny joint.

 

[Amvcane]

Dave, I know older Kioti CKs had a problem with trans cooler lines failing from vibration and fixed the issue with some redesign.
Here is a pic of my 2012 CK35 trans cooler lines (same left or right). This is how the tractor came from the factory. If your lines are the same could you please let us know where the leak is so I can keep an eye on that location.
If your cooler lines are different could you post a pic so we can see where changes were made.
Thanks Andrew.

 

[DaveK OR]

I'm reasonably sure that the front end of the cooling system doesn't have the problems I've encountered. I'll try to insert a couple of images that should be useful. These are from the Bobcat online parts catalog, and the CT235 is nearly the same as the Kioti CK35 (with hydrostatic transmission). Anyway, The first failure I experienced was in the Joystick Valve Group (FEL Joystick),
The tube in the image below labeled No. 33. The failure was at the double-o-ring connection, where the tube is welded to the connection boss.

The most recent failure was in the HST External Hydraulic Line Group, in the part labeled as No. 17 in the image below. Again, the failure was where the tube is welded to the double-o-ring boss.

Bobcat (and probably Kioti) recognized the problem and have changed the design of some replacement parts. For the joystick tube, I believe that connection now includes a collar of some sort that adds reinforcement to the weld area. For the long hydraulic cooling tube, they have added a mounting bracket to limit vibration of that line. They may well have also added the reinforcing collar to the weld between the tube and the double-o-ring boss.

As far as what to watch, I would consider ANY of those hydraulic hard-line connections that have the tube welded to the double-o-ring boss to be suspect, especially if the hydraulic line is long and subject to vibration. When they fail, the crack is so very small that it is virtually impossible to see unless the line is under system pressure. That pressure can be very high indeed, so caution is advised when searching for the source of an active leak... you don't want to have hydraulic fluid injected into a body part that gets too close to the leak.

I hope this helps. If you do find a leak, re-welding is probably a bad idea. It's nearly impossible to get the hydraulic fluid cleaned out of the crack, so you'd end up with a bad weld. As far as silver-soldering the joint is concerned, the joint gap is so very thin that I doubt you could get any silver solder to flow into it.

 

[Amvcane]

Thanks Dave,
I was thinking that you had the (older) common leak at the trans cooler.
Now that I see where you are talking about I will keep an eye on those areas when greasing though I don't ever recall reading about leaks in those areas.
Thanks, Andrew

 

[DaveK OR]

Those leaks don't usually start out small. They'll usually begin suddenly when the hydraulic system is at high system pressure (e.g. a heavy lift with the FEL or heavy digging with a backhoe) and spray a lot of hydraulic fluid. Once the load is off and system pressure is down, it slows to a small but steady stream. Once you stop the engine, the leak will stop as well. If you are working in an area where you can't see the fluid on the ground, you probably won't notice it until the fluid level is low enough to impact hydraulic performance.

 

[lilranch2001]

I had the same line crack 2-3 years ago, replaced it and also took a floaty pool foam "stick" cut it and put it around the line between the line and frame of the tractor), and it seems to have dampened the vibrations

 

[SirMaxwell]

I have edited the title of this post to reflect the fact that the leak resulted from cracked welds at hydraulic hard-line connectors. The original post continues below.

The hydraulic cooling line (the long one on the left side) on my CT-230 has suddenly developed a leak at its rear connection point. Having removed the line and cleaned it up, I can't find a crack in the weld at that connection so the most likely culprit is failure of the o-rings on that connection. Can anyone advise an Auto Shop (NAPA, for example) replacement for these o-rings? The Kioti parts diagrams show these as Number 04810-00200. These are higher durometer o-rings designed for high pressure, so I can't use the softer ones that are a lot more common.

It is still possible that the weld on that connection has cracked, but it's too small to see. I had that happen previously on a different line, and had to replace it. In that case you could see the hydraulic fluid spraying out under pressure from the crack, but it closed up invisibly tight when not under pressure.

I know I could get these o-rings from Bobcat, but that is a 60 mile trip, and there's a NAPA store just down the road.

I know its been a while, and sorry for that.

I had the same problem, small crack hidden in the weld. Carefully ground it most of the way down, flooded it with brake cleaner and had a professional welder redo the weld. That was 150hrs ago. $10 and 1 hour work.

I will add, that the same style of joint you showed above, the second long tube, I had a small leak and thought, uh oh, here we go again. But when I cleaned it up and dried it, the oil was seeping from the actual joint surface. So, I tried to snug it down a bit. While doing this, it felt a little "squishy" like I was going to strip the threads. So I stopped, took it apart and what did I find? There was a crack around the hyd oil flow hole in the bolt. So as I was tightening it, it was pulling the crack. Had I kept going I am certain it would have snapped. So, replaced the bolt and O-rings.

( 1ea 6696165 - Bobcat - Bolt, Joint , 2ea 6694137 - Bobcat - O-Ring) or (1ea T4620-37092 Kioti Bolt, Joint, 2ea 04810-00200 Kioti O-Ring)

I know I am rambling atm but, that Kioti O-Ring number also comes up as a Kubota and Cub Cadet O-Ring. I know, everyone uses O-Rings, but the part number is the same. Must be a generic or manufacturer number.

Max

 

[BobLou]

Same thing happened to me, on both side of the tractor
I cut the the line took out 5 inch and welded 2 hydraulic nipples males. then I had a 5 inch hydraulic line with 2 female union made to insert in between my cuts, now the rubber hydraulic line takes the vibration. I did this at about 700 hours.