Nagging hydraulic leak

[jinman]

I've had great luck with the hydraulics on my 2000 model TC45D and had no problems until recently. Last year, I had my hydraulic pump seals replaced on my tractor and all went back together nicely except for one pinched o-ring I had to replace at the diverter valve. About 3 months ago, I developed a spewing hydraulic leak where the high pressure line bolts to the diverter valve. That's directly under the right foot rest of the operator's platform. The leak was so bad that the whole bottom of my tractor had a hydraulic bath. I had measured my pressure at exactly 2500 psi, so I know the pressure is not too high. I figured I had not tightened the fitting properly. When I removed the nut, I found that it and its lock washer seemed to not tighten the flange properly. Below are some photos that show the flange, o-ring and screen. Notice that the pipe is made to slide straight upwards between the hydraulic pump and diverter because you cannot move the pipe horizontally to get it out. That's why there is a slot on the top of the flange. It has to slide onto a stud and then a nut added. The bottom uses a bolt. I've included some photos of the pipe installed.

On the hydraulic pump end, the flange has four bolt holes. If you look at the illustration below (Item #9) it shows the pipe has only two bolts on the flange and the diverter end does not show the slot. I found by research that the TC35D's hydraulic pump flange only has two bolts. With its pressure being only 2300 psi, only two bolts are required in the pump. I have never had a problem with the pump flange and seal leaking, only the diverter valve flange. The tiny o-ring on the diverter end just seems to blow out and spew hydraulic fluid. It's frustrating to me because it was never a problem for almost 12 years and 1700 hours. Now, a "simple" job has turned out to not be so simple.

After replacing the o-ring AGAIN, I put a flat washer under the bolt head to help apply pressure. I think the slot may have deformed or the bolt head and lock washer could not apply even pressure, allowing the flange to move outward enough to blow the seal.

After repair, I went to work boxblading my dam and moving some rip-rap with the loader. A whiff of hydraulic fluid told me to look down and my heart sank. It was spewing. Obviously, I've bent the pipe or flange so much that with the normal hardware and o-ring, sealing is NOT possible. So it's time to go to Plan B on getting the seal as it should be.

 

[jinman]

So, on Friday morning I started with "the final" fix before I order a whole new pipe. I'm sure I've bent this pipe or messed up the diverter side flange. If my Plan B doesn't work, I'll spend the $135 for a new pipe.

Below is what I did in the illustration. As I said before the pump side is no problem at all. I have used the same o-ring seal on the pump since I changed it when I first got the pump repaired. It just works perfectly. Since the diverter flange has a tiny thin o-ring, I found a fat Viton the same diameter as the original and an HNBR o-ring that would fit into the center of the Viton. There is plenty of metal sealing surface for both of them if the little thimble looking screen is removed. I know it's there to catch debris, but only if the pump completely destructed would there be any metal. The fluid is drawn from the reservoir through the main hydraulic filter and only goes through the main pump before coming to the screen. I'm gonna run without it so I can put double seals in this flange.

Next, I went to Tractor supply and bought grade 8 flat washers. I put three big flat washers on the stud and still had plenty of threads for the nut and lock washer to go on. The big flat washers span the gap well and provide even pressure on the top of the flange. With trembling fingers, I started the engine and checked for leaks. Yippee! None were found. I put pressure on the system several times to open the relief valve and there were no leaks. I then went and used the tractor to boxblade my road I made to haul materials to my pond dam project. A check afterwards showed the fitting still dry. So, I think I'm going to call this problem fixed. I've got my fingers crossed that the dual o-rings will solve the blowout problems.

Again, I don't blame this problem on anybody but myself. I'm sure that if I'd been careful not to bend the pipe while first removing the pump and also didn't spread the slot on the flange, I'd be fine with the OEM parts. As it is, I'm correcting my own bonehead mistakes. I'll report back if I run into any problems. I don't know if there's a moral to this story or not, but I'd sure say that what looks simple can easily be the thing that eats your lunch.

 

[Harry in Ky]

The viton O ring of slightly thicker material was my first thought as well, but did you think to pass a large file over the length of the flange just to get a feel for the flatness while it was off? The design of the tube/flange combination just looks like a recipe for distortion if the pump end gets shoved one way or the other while the pump is removed and installed.

 

[jinman]

Harry, I did not check it for flatness because I didn't think of a file. I looked for my stainless 6" scale, but didn't find it and just blew off checking the flange for flatness. That additional oversight may yet prove to be a problem. My fingers are crossed in a double King's-X that it will be okay, but I'm NOT gonna pamper it. I'll use it normally, and if it blows, it blows.:confused3:

 

[thclimer]

Nice write up with pictures, sounds like you fixed it!

It's hard to believe you would have bent the flange without remembering that you really twisted or forced it somehow and since you did not do that I wonder if there is a specified torque for the nut and bolt. Maybe you had them too tight or too loose?

Anyways good to know your back running.

 

[jinman]

It's hard to believe you would have bent the flange without remembering that you really twisted or forced it somehow and since you did not do that I wonder if there is a specified torque for the nut and bolt. Maybe you had them too tight or too loose?

Anyways good to know your back running.

Tim, I have to admit that I DID bend the tube a tiny bit when I took off the hydraulic pump. There were two bolts in the pump's flange that I could not get without a universal joint adapter. I pulled/bent the tube down off the diverter so I could slide the hydraulic pump out of its engine mount. I've hinted at that, but never really 'fessed up to it. That's why I'm so willing to accept my transgressions and buy another flanged tube if this one continues to leak. I will say that I've straightened the tube so well that after bolting up to the diverter, I only had to stick the bolts in the flange at the pump and turn them. The flanges are in perfect alignment to each other. This is really not a design problem as much as my poor technique.:ashamed:

Oh yes. . . I bought replacement bolts at the dealership for the pump's flange. The bolts are the same size, but their head size is 14 mm instead of the 17 mm of the originals. Smaller bolt hex heads make a world of difference in this tight spot.

 

[TO_Bud]

Another great write-up Jim, I'll have to bookmark your work here as you seem to be the harbinger of things to come on my TC40D. Your tractor has more hours than mine but I have already corrected some things on my machine based on your experiences, Thanx for that. Hope your fix lasts.

Bud

 

[wdchyd]

Something to think about Jinman, viton orings are great for heat related issues but do nothing for extreme pressures....

The best case for extreme pressures for overkill would be to find an oring with 90 durometer (instead of the standard 70 durometer)

Also if the oring is too fat, it may squoosh in between the flange and housing during torque-up, so dia is critical....

That said, Hope it lasts this time for ya...:thumbsup:

 

[RickB]

I think you will be OK. Sometimes flange fittings on tubing need to be tightened in a specific order to get the proper clamp load if the tubing is tweaked a little. Perhaps tightening the pump end first allowed a minor mis-alignment of the diverter valve end that could not be corrected by the limited clamping effect of the small attaching hardware.

 

[jinman]

Thanks guys! Since I put a HNBR o-ring in the middle of the Viton, I now have two o-rings in there. Most likely the HNBR will do the seal since it fits perfect up against the Viton so that the Viton backs it up to keep it from blowing out. It may work and then again. . . I've thought that before. I won't be betting my Social Security check on it.

 

[Carykong]

Jinman, Could you have spliced in some flexible rubber hydraulic line to mitigate the bend? Just wondering.

 

[jinman]

Jinman, Could you have spliced in some flexible rubber hydraulic line to mitigate the bend? Just wondering.

Ha! I thought of that, but by the time I got two splices done, it would cost as much as a new pipe. I'm sure doing the job right has a lot more to do with success than anything. If I had the new pipe, I now have all the proper tools and technique to do the job right, without any "folding, spindling, or mutilating" of the pipe.:laughing:

 

[jinman]

After hauling 5 loads with my dump trailer, the stinkin' seal blew out again.:mur: This time, I'm ordering the whole pipe and will try that. I'm also going to talk to my dealer's service manager to see if he has any tricks. This SHOULD NOT be happening. I'm not working the hydraulics or trailer hard. The dump trailer is hooked to my remotes, but it is only loaded with 4-1/2 yd of material in a 7 yard bed. It's not hooked to my 3PH, but to the drawbar, so the only time the hydraulics work are when dumping the trailer.:confused2:

 

[wdchyd]

Jim,

Just for yuks when you take it apart again.....could you measure the "Groove" thickness and outside dia....

(assuming you have a set of calipers of sorts)

Bill

 

[Hooked_on_HP]

After hauling 5 loads with my dump trailer, the stinkin' seal blew out again.:mur: This time, I'm ordering the whole pipe and will try that. I'm also going to talk to my dealer's service manager to see if he has any tricks. This SHOULD NOT be happening. I'm not working the hydraulics or trailer hard. The dump trailer is hooked to my remotes, but it is only loaded with 4-1/2 yd of material in a 7 yard bed. It's not hooked to my 3PH, but to the drawbar, so the only time the hydraulics work are when dumping the trailer.:confused2:

Jim are you always using the dump trailer when it blows the o ring.
Bill

 

[jinman]

Jim are you always using the dump trailer when it blows the o ring.
Bill

No, not at all. Most times I've been using the loader. When I get the new pipe in, I'll measure the pressure, but I have no reason to believe it is anything but correct. We'll see. . .

I'll try to measure the gland (groove) dimensions (depth & diameter). I think I have my micrometer stashed away somewhere.

 

[jinman]

Ordered the hydraulic tubing this morning. It should be at the dealership on Wednesday.:thumbsup:

 

[jinman]

Tubing arrived Wednesday as promised and I picked it up yesterday. This morning, I decided to tackle the job of replacement. The first thing I did was crawl under the tractor and inspect the old tube. As I expected, I had parts of two o-rings hanging out the back side of the diverter/regulator end flange (1st photo). The Viton is red and the HNBR is green.

When I removed the tubing, the Viton ring had exploded due to over-compression. The HNBR had an extruded "tongue" on one side (2nd photo). I compared dimensions of the old part to the new one with my antique micrometer and found them to be as close as I could measure. The o-ring that fits is supposed to be .969" o.d., and .0945" o-ring thickness. I measured the gland at .9515" wide and .0915 deep. That means the o-ring diameter is slightly compressed to fit into the gland and it is only .003" thicker than the gland depth. My gland diameter measurement may have been off a bit because one of my tips is nicked on my old micrometer, and it's hard to measure diameters on such a shallow gland.

The real story was when I put the micrometer's edge across the flange (final photo). The ends of the flange were slightly bent so that the center around the gland had a gap when the flange was tightened. You can't see light in my photo, but I could easily see it under the mic on the old tube flange and not on the new one. The new flange is perfectly flat.

I installed the new tube carefully, tightening the diveter flange end before tightening the four bolts into the hydraulic pump. I cranked up the tractor and raised the bed on the dump trailer until the cylinders extended to the end and the pressure relief popped. I did the same with the loader. NO LEAKS!. I'm not sure it's fixed, but I've done my best to do the job right. I put the correct o-ring in from New Holland instead of my experimental ones. Everything is back to stock and I've got my fingers crossed that this time it will all be good.

I didn't read the system pressure, but I'll try to remember to do that tomorrow.

 

[wdchyd]

Jim,

The only thing I can think of is the material that the flange is made of is too thin or not strong enough tensile strength to withstand the pressure spikes.....

the oring failure does look like extrusion through a gap, so if the flange flexes under pressure it may open up on the side allowing the oring to blow...

I don't have my oring info at home but can check at work next week but it seems as though the cross-section of the oring should be thicker than .003......I'm thinking it should be about 10 to 20% thicker than the depth of the oring groove....

On the old extra tubing you could weld up some kind of reinforcement on the side of the flange to stiffen up, then surface grind or mill the face flat if the welding distorts the flange.....

It just looks as though the flange with only 2 bolt holes on the long sides are not heavy duty enough.....allowing to flex under pressure

Just my :2cents:

 

[jinman]

Bill, your guess is as good as mine for sure. I think your idea of a 90 durometer o-ring is a good one. I had two of the stock o-rings and just decided to go back completely stock. After all, it worked for 1700+ hours that way and didn't start leaking until I took off the pump. Not only did I bend the tubing some when I first took it off, but I just remembered that I tightened the flange down the first time with the o-ring out of place. I always coat o-rings with a tiny bit of grease for sticky, but somehow got the o-ring out of the gland. That means I could have bent the flange when putting in the o-ring. I can't tell you how stupid I felt for botching this job so badly. It was a bad day. The same day I cut the o-ring inside a quick connector when I installed the loader hoses.:confused2: I completely lay this problem at my feet. This one's on me.:ashamed:

Also, I wouldn't swear by my numbers and measurements. The numbers I came up with for the gland are based on the oem o-ring dimensions and my measurements. As you said, .003" is not much crush on an o-ring. Not being a hydraulic expert, I don't know what the normal compression dimension is. I could easily have been off a couple of thousands with my measurement. I really need to get a dial indicator micrometer instead of this old antique with a vernier scale.

Thank you very much for your advice. When I was at the dealership to pick up my tubing, I first stopped and talked to the service manager. I asked him if he had ever had one of these leak. He told me they had and that they always just replaced the tubing to fix the leak. I think this part has to be handled carefully instead of being monkey-fisted like I did the first time around. Just keep your fingers crossed for me that this time the oil stays instead of sprays.