Help me Change a Kubota Quick Coupler

[SteveHGraham]

Because my John Deere garden tractor survived my repair attempts, I am moving on to my Kubota.

I have a bad hydraulic leak from the manifold (guessing at the name) that hooks up to the FEL. Yesterday I hosed the crud off the tractor, and I parked it overnight with a clean sheet of newspaper under it. At least an ounce of oil leaked out. I am uploading a photo. There are two quick couplers at the rear of the manifold-type thing. It appears that the one on the right is leaking. Because there is no oil on the body of the coupler, I believe the problem is with the threads under it.

It looks like there is a coupler, then a pipe with two threaded ends, and then some kind of elbow. I assume I should replace all three parts, because I can't tell which one has the problem.

If you look closely, you can see pipe wrench marks on the round (thanks, Kubota) nut under the coupler. Based on this, I conclude that a highly trained technician has already attempted to fix the leak, using the MIT brain trust approach.

What's the right tool for getting this coupler out? I have some crowfoot wrenches on the way. Maybe I can get one in there. I can't understand why Kubota would use a nut with only two flats, but my best guess is sheer sadism.

I don't know if I'll be able to turn this thing as well as I need to. Wondering if I can find a real hex nut to replace it. If so, I feel like I should get rid of the other idiot nut on the left connector while I'm at it.

I think I'll have to remove the flare nut to the right just to get room for a crowfoot wrench.

[SteveHGraham]

Since posting my sad tale of woe, I got the connector off. I realized it was going to be discarded anyway, so I didn't care if I marred it. I put Vise Grips on the body, and it came out easily.

It looks like what I thought was a nut under the coupler was really part of the coupler body, so Parker, the coupler manufacturer, is to blame for the ridiculous design with only two flats. I am thinking I may put more flats on the replacement with the bench grinder.

I don't think there is much hope for getting a crowfoot wrench on a new one to install it. I don't know how the original installer did it. Maybe I'm wrong.

It looks like a replacement is $18, so I am inclined to buy one, install it with Vise Grips, and see if the joint leaks. If not, I can leave the chewed-up coupler on the tractor and worry about getting the right tool later. If it does leak, I will be no worse off than I was yesterday.

[SteveHGraham]

Believe it or not, there is more to the story.

I Googled around, and I read that hydraulic connectors are supposed to have sealant on the threads. I don't have anything fancy on hand, but my jar of Home Depot pipe dope says it's good to 3000 psi, which can't be too far from the pressure in the lines, which are only rated to 5300. I decided to reinstall the coupler with pipe dope on it, to see what would happen. I used Vise Grips to put it back on the tractor. It's not the best-looking coupler in the world, but then it was messed up before I took it off.

I put a bucket with clean paper towels in it under the tractor, and I ran the FEL for a bit. Now I'm going to leave it alone and check it tomorrow. Who knows? Maybe I improved it. I spent a few minutes waiting to see if it would leak, and nothing appeared. I left the bucket slightly off the ground, thinking maybe it would keep a little pressure in the lines.

If the right connector had no goo in it, I assume the other ones are also dry. Maybe once my crowfoot wrenches arrive I'll be able to check them.

[John Hasler]

If the nipple has threads that look like NPT it's actually NPTF Dryseal. If you replace it with an NPT nipple it is likely to leak.

[warmstrong1955]

Teflon pipe dope is generally the stuff used by manufacturers and rebuilders on NPT threads. Seals better than the regular for hydraulic systems.
That is all I bought for my mechanics in the mines too.
Loctite, and Permetex are the 2 brands I bought most often.

So if it still leaks, assuming it is leaking at the threads, pick up a tube of the good stuff.

[liveaboard]

There are different systems; tapered threaded seal on the thread. Straight threads [also pipe threads with the same pitch and all] use either an oring or a crush washer of aluminum or copper.
Those quick couplings are surprisingly cheap. My local tractor shop only has tapered thread ones, but everything else in the shop is straight thread. I had to cut a taper into a straight nipple to use them.

The crush washers work ok if the faces are all parallel, but suffer from parts loosening up due to vibration or torque on the hoses.
Tapered ones get put in with great force, and can need serious force to remove.

often the fittings are so close together, you need to take out several to get to the one you want to work on.

Most hydraulic components are fairly cheap now, but the control blocks are still really expensive.

I have a leaky fitting on my FEL too.
A banjo fitting with misaligned faces. If I could find a new one, it would probably cost $1. Since I can't, I need to make a mandrel to mount it on the lathe.
Not today though.
Maybe tomorrow...

[John Hasler]

There are a number of these fittings that look superficially like NPT and will seem to interoperate. On old farm machinery I frequently discover instances of an NPT pipe fitting having been substituted for the correct hydraulic fitting (I've done it myself, actually). Sometimes it works, given enough teflon tape and torque.

https://www.hydraulicsdirect.com/Fittin ... s/1934.htm

[rrnut-2]

Ya, what John said. Kubota is another brand that uses a lot of their own fittings, so look at it good before going to Tractor Supply or whoever.

Jim B

[SteveHGraham]

This morning it looked like a drop of oil had hit the paper towels. For all I know, that oil was still on the tractor after I reinstalled the coupler, so it may be that the leak is gone. In any case, a drop is better than an ounce.

The threads are tapered. The coupler says something like Parker Series 60. Eighteen dollars on the web, but I would have to drive 20 miles to buy it.

[warmstrong1955]

Pipe dope can do wonders. NPT on hydraulic systems, is archaic, often leaks, and we always doped up the threads.
Still....they be the most prone to developing a leak.

FYI, The Parker 60 series couplers are interchangeable with Aeroquip (now Eaton) FD45 quick-couplers, as well as a lot of other brands. It is the most common. Any hydraulic house can cross ref them.

The Kubota tractors I have been around, again, we used them for transportation & mat'l handling in the mine, were all "Americanized". I don't know if Kubota did them all that way, or just the ones headed to North America.
JIC fittings on the hoses, valves and cylinders were SAE O-ring boss, or NPT. Normal stuff.....for the US and Canada anyway.

[SteveHGraham]

Do any of those interchangeable couplers have hexes cut into them instead of two flats?

[warmstrong1955]

FD45's have a hex.

See page 14.

http://www.eaton.com/ecm/groups/public/ ... 369360.pdf