3400 power steering cylinders

I just installed my newly rebuilt power steering cylinders, and they leak! The rebuilder cut the cylinders open with a pipe cutter to replace the seals, then tig welded them back together carefully to avoid cooking the seals. I installed the cylinders on the back ends and left the front ends loose. I fired up the tractor to make sure I had the lines hooked up properly. When I turned the wheel left, the left cylinder pushed out, as it should. The other side retracted as it should. The right side worked in the proper direction also. I then hooked up the front end of the cylinders and turned the wheel with the front end jacked up. The front wheels turned properly. I then lowered the front end to the ground. With the tractor running I filled the power steering pump reservoir. The left cylinder started leaking fluid past the wiper, making a puddle on the floor. I replaced the cap on the reservoir and found that both cylinders leaked when turning the wheel, and the wheels turned but slowly. What happened? I should mention that I have upgraded to the new style power steering pump with integral reservoir and I had to replace the spring in the pressure relief valve with a weaker one to bring the pressure down from 1200 psi to about 750 psi. It's a bit higher than the recommended 650 but I figured close enough. I also replaced the power steering lines and rebuilt the steering box. The cylinders are leaking when I turn the wheel even though the wheels are not turned to the stop. Any thoughts appreciated. I bought this tractor in July and have been fixing it since then... this was the last thing keeping me from using it.

Just thought of something. I think I may have reversed the cylinders. The rebuilder said that they are not dual-acting. The return side doesn't apply pressure, it just allows fluid to exhaust back through the valve and back to the reservoir. If I have the cylinders reversed, they are actually pressurized on the return side, which is not designed to hold pressure therefore the fluid is leaking past the wiper. To test my theory I must reverse the cylinders to the opposite sides of the tractor. Does this sound right? Thoughts appreciated, thanks. :wink:

I just remembered that the rebuilder labeled the cylinders L and R, but I had marked them with a scratch awl and lo and behold, he marked them opposite to how I did. I installed them according to his marks, and therefore they are on the wrong sides. Is pressurizing these cylinders from the wrong side like I have done likely to have ruined them? :shock:

The cyls are 2 way, thats why they have 2 lines. Either did not put u cup in rod end only put wiper or melted them. They should have never been cut apart not really any servicable parts inside. I know youll proably never get the shop to do anything about their screwup.

I"ve got a 3600, which should be configured the same as your 3400.

Your power steering control valve has two connection ports for the PS cylinders on each side. An UPPER/FORWARD and a LOWER/AFT connection.

Your power steering cylinders should have two connections facing up. An INSIDE and an OUTSIDE connection.

The UPPER/FORWARD connection on the PS control valve connects to the INSIDE connection of respective PS cylinders.

The LOWER/AFT conn on the PS valve connects to the OUTSIDE connection of respective cylinders.

Thanks, sixbales. I swapped cylinders and made sure to hook the lines up properly, all to no avail. Both cylinders leak around the rod wiper upon retraction of the rod. Steady, almost like a stream of pee. Shaun, you were right. I looked in the fsm and it clearly states the cylinders are double-acting. The fsm schematic of the power steering control valve also shows pressurized fluid pumped to each cylinder port at different times. So they are not (as my rebuilder guy said) single acting cylinders. He said that they were weird, he had never seen anything like them before. I guess that was a bad sign. Seemed like a good guy though, so I will call him tomorrow to see if he will try again. :?

Can anyone explain to me how my power steering cylinders work? All other double-acting cylinders I have seen have one port on each end. The cap end has a port that allows oil to push the piston out and extend the rod. The rod end has a port that allows oil to push the piston in and retract the rod. Why do my cylinders have both ports on the cap end? Is there an internal tubing or passage that carries oil to the rod end to push the piston in and retract the rod? If I can understand my hydraulic cylinders, maybe I can help my rebuilder understand them. Could his mistake simply be that he used the wrong type of seal/gland on the rod end? Please advise. I put a call in to him today but haven't heard back yet.

(quoted from post at 18:49:29 11/11/12) The cyls are 2 way, thats why they have 2 lines. Either did not put u cup in rod end only put wiper or melted them.

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Shaun, I think you are right. The rebuilder may have only put a wiper on the rod end since he seemed to not understand the cylinders. If he only put a wiper on the rod end they might not leak when wheels are jacked up off the ground since there is no real resistance. With wheels on the ground, there is enough resistance to blow past the wiper in the absence of a proper u cup. Makes sense. He showed me the rod end seals and said they were weird. Maybe he just replaced them with a wiper and called it good. I don't think he melted the seals on the rod end since they are replaceable by simply removing the snap ring. They would not have to be installed until after he welded them back together. He cut them open to replace internal piston seals, so those had to be in place when welding back together. If my guy can't find the proper rod end seals I will have to get them from New Holland for $87 each, but at least they are still available.

Hooking up the lines wrong will not make it leak. It
simply will not steer. Leaks due to faulty rebuild.

Heard back from my rebuilder today. He told me the seals he installed on the rod end were not high-pressure seals because those he removed did not seem to be high-pressure cup seals. He also told me that the shop he gets seals from can get a high-pressure cup seal for my cylinders, so he can fix the problem. I will report back.

Got the seals yesterday from a shop in Worcester, MA called "Mechanic's Bliss". Great place. They match seals and make hydraulic hoses. My cost for 2 high pressure seals and 2 rod wipers was $25. New Holland price for the same parts was going to be $176 plus tax. My rebuilder is going to install them for me. I might do it myself except it's a bit tricky to remove the old ones given that the rod will still be in place. Will report back.

Most steering cylinders for tractors and some forklifts are what's called tube in tube. One port goes into the inside tube and the other to the outside then to the other side of the piston. You can tell you have that type when both ports are on the same end. For a complete rebuild on a fully welded cylinder(one in which the gland is not able to be removed) the cylinder must be cut apart. I cut out the old weld in a lathe, but it must be the butt end of the cylinder. That way the seals that are installed will not be affected by the heat of welding. It sounds like the guy that did the work for you did not know how to do the job properly.

Thanks Hydrofixer, that clears it up for me. To wrap up this story, I brought the cylinders back to the guy with the proper seals. He installed them no charge and I am in business. All is together and steers great. Of course now I have a bad generator to deal with...