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.