B21TLB Replacing oil cooler return pipe

[kubotaswede]

20 years ago I imported a B21TLB to Sweden from the US. The machine has been incredible problem free. However, yesterday I identified a hydraualic oil leek coming from the oil cooler return pipe located at the third bend counted from the front. A section of the pipe is corroded and the leak is significant. Replacement or repair is mandatory. Buying the spare part (Kubota no 32721-39323) in Sweden is impossible and Kubota dealers in the US are not allowed to export. So how do I solve this problem? The first issue was to remove the faulty line which required removal of the hood, grill, hydrualic oil filter protector and protecting cover under the seat. Needless to say all bolts were stuck so heat and long handles had to be used. Now the pipe is loose but I can not remove it from the tractor due to its complex form and the narrow spaces in which it is running. My questions are:
1. Anyone know how to operate the pipe to get it off the tractor in one piece? Do I have to remove more items or should I just cut the pipe into three pieces?
2. Would it be safe to replace the major part of the pipe with a hydraulic hose or should I just remove the corroded section, bend a fresh 12 mm pipe and connect it back with shear ring connectors?
3. Is welding or hard soldering of a corroded pipe to recommed should I get it off the tractor in one piece?
Any suggestions would be highly appreciated.
Lars

 

[Harry in Ky]

I have repaired many rusted out steel hydraulic lines by cleaning up the surface and brazing over the affected areas. It's worked for me many times and solved problems for years. If yours is a 12mm line (a common size with Kubota) I've also done sectional replacement type repairs with new tubing and compression tube unions. If there's room for them, they work quite well, even on high pressure lines. I doubt a cooler circuit is all that high in pressure. You could cut the tube into manageable pieces, repair or replace the damaged section, and re assemble it in place with unions.

Something like this.

Metric Union Straight Compression Set Zinc Plated Steel

Bel-Metric sells metric hardware & specialty automotive supplies worldwide. Visit our website to purchase metric fasteners, nuts, bolts, screws, washers & more.

belmetric.com

Replacing some or all of it with a hose is another option, but this might be simpler.

 

[Smokeydog]

Excellent advise. Add there are many types of weld-on poly hose supports to secure a hose if you go that option.

 

[JWR]

No Kubota dealers in Sweden? Kubota in Japan can probably export the hose assembly to you. The hard part is making contact with the right people unless you have Kubota dealers in Sweden.

 

[kubotaswede]

Yes, there are Kubota dealers i Sweden. They rely on spare parts from an EU supply organisation. They can usually not deliver parts to US models although the correct part number is presented. I lean towards following the advice of Harry in Ky (Thank you!). The problem for me with that solution is that I have to replace a part of the line that is bent i two different dimensions quite near to each other. I have tools to bend waterpipes so i will try them. But I am still wondering what I am missing being unable to remove the loose pipe from the tractor. It seems like a 3D puzzle...
Thank you
Lars

 

[CurtisC]

The good news is it's a low-pressure line. Some thoughts:
Determine where pipe can be cut for removal, locate best support locations each side close to cut for new 2 or 3 piece hard return line. Mark retained and damaged sections for new lengths to account for new hose connections during reinstall and save for fab templates. Have a tubing or machine shop fab up the new pieces and trim the old (if saved) and clean. Reinstall with new supports, connector hose and clamps.
I think it goes without saying that it's best to replace the whole line (with minimal number of pieces) unless you're sure the rest of the line is good or fab costs are exorbitant.

 

[Harry in Ky]

Yes, there are Kubota dealers i Sweden. They rely on spare parts from an EU supply organisation. They can usually not deliver parts to US models although the correct part number is presented. I lean towards following the advice of Harry in Ky (Thank you!). The problem for me with that solution is that I have to replace a part of the line that is bent i two different dimensions quite near to each other. I have tools to bend waterpipes so i will try them. But I am still wondering what I am missing being unable to remove the loose pipe from the tractor. It seems like a 3D puzzle...
Thank you
Lars

I have used the compression tube unions a number of times. I also keep old bent or damaged lines to use for similar repairs for that very reason. All too often steel lines can be a royal pain to get out and put replacements back in on many Kubota models. A short section of like sized tubing and a couple unions can make a two or three day project into a one or two hour job. The end result can be just as good.

 

[kubotaswede]

Thanks for generous and wise advice. I will cut the pipe in three pieces and let the local hydraul store make the bends and reconnect with compression tube unions. It is a true relief to give up the 3D puzzle that has been going on for several hours now challeging my mental capacity.
Greetings
Lars

 

[rScotty]

Another way would be to replace the metal pipe entirely with a hydraulic hose using standard swaged connections on the ends.
While you are in there, search for some old posts and take a close look at the suction hose from sump to pump. I think I recall there being some posts about an upgrade to that suction hose design. Not sure if it was on your model, though.
rScotty

 

[CurtisC]

Another way would be to replace the metal pipe entirely with a hydraulic hose using standard swaged connections on the ends.
While you are in there, search for some old posts and take a close look at the suction hose from sump to pump. I think I recall there being some posts about an upgrade to that suction hose design. Not sure if it was on your model, though.
rScotty

Thread link below maybe what rScotty's referring to. Not sure if the B21 and B26 are plumbed similar, but there's a rubber elbow at the B-26 pump that is susceptible to cracking due to hardline vibration. At the end of the thread, you'll see Kubota's fix was adding a piece of hose to further isolate the pump from the line. While getting new parts doesn't sound viable for you, cutting the pipe and adding short piece of hose might be a wise preventative measure while you're in there assuming the 21 has the same general suction line setup.

Suction Line replace

 

[nyone]

I would try to weld a patch on the line while it was still in the machine. It's a low pressure line so something like JB weld may possibly even work just fine.

I have tig welded high pressure hydraulic lines before. It took a few hours to chaise pin holes but the replacement piece was connected to a $1000 cylinder. That unit hasn't leaked in 5yrs and i still own it.

 

[kubotaswede]

After dividing the return pipe it easily came off the tractor. Mostly superficial corrosion but one quite large hole (2 mm) in a corrosion pit on the underside of the pipe (see photo). I have bought a new pipe to bend and a compression union. The structure is quite complex (see photo) so I am not sure I can get the bends right. Would it possible to repair the leak with a small MIG weld on this low pressure pipe? Or should I go for trying to bend the new one?

 

[Smokeydog]

Welding depends on the welder and condition of the pipe you can’t see. I once welded a pin hole leak on a Kubota B20 hard line for the power steering circuit on the tractor. Thought it would be a temporary fix but was permanent over 10 years till I sold the tractor. I have more luck than skill.

Had the B20 for over twenty years and B26 since 2016. Excellent machines for our small hillside farm.

 

[rScotty]

I've done a lot of similar repairs working as a tinker in the third world. All done with oxy/acetylene.
I wouldn't weld it, I would carefully form a patch out of tube material that covers about half the diameter of the pipe. Then use silver-braze for strength and flowability to braze the patch over that whole area.
If it is beyond your ability, I am sure there is an old torch welder in your area that can do it. All it takes is patience and a good hand with the flame.
rScotty

 

[kubotaswede]

Thank you rScotty. This is far beyond my ability. But the good news is that I managed to bend a replacement pipe for the foremost half which fits quite well and connects to the rear half with a compression union. I am now replacing the hydraulic oil and the filters. The hydraulic filter was not easy to find in the EU but I hope it arrives this week. Then I can test for leaks and hopefully the tractor is up for use after that. I thank the forum for interest and good advice in my problem. It has helped me to maintain confidence during the repair process. Thank you all!
Lars