3-point hydraulic problem still present

[Ben755]

​My FX28D still has a slight jump in the 3-point hydraulic system after replacing the main piston seal and all the o-rings. Apparently, the cylinder is still losing
some pressure and cannot maintain the control valve setting without constantly correcting. I did notice some fluid leakage around the pressure and return lines
going to the quick connects and on to the FEL control. These lines are rigid steel lines that are held to the 3-point housing with bolts and brass compression type
washers. The line from the pump goes into the front lockout valve plate and has the same type of connection, but it does not leak. Could the leaking pressure line
connection be causing the jump problem, and where might I find possible compressing replacement washers ? Would o-rings be a suitable replacement for the washers ?

 

[clemsonfor]

I am not an expert but I do not think a leak would cause a jump. That's just my opinion but that is just a gut feel. I am around a lot of logging equipment and yes its a lot larger and the pumps on that stuff pump HUGE volumes of fluid but when that stuff leaks even bad the only effect is less power of whatever the hydro is going to. Like a grapple, a leaky cylinder can leak BAD but still do what it needs, unless a fitting busts or hose bursts you almost always maintain pressure to do what you need to do.

 

[winston1]

I agree with clemsonfor, a leak in your lines is not causing your jumping. I would guess it is coming from the 3 point control valve. Having replaced your lift piston o-ring would seem to rule that out. Always a chance a little trash under the relief valve. No way to make a good diagnosis just based on what it is doing. However, once your lift is in a certain position if everything is holding as it should the hydraulic fluid is then just circulating by the control valve and lift piston. The jump is caused because of loss of fluid somewhere in the 3 point lift circuit. Nothing to do with any leaks before getting there. Make sense?

 

[LD1]

When you shut the tractor off, does the 3PH bleed down at a noticeable rate?

Not sure how your machine is plumbed, but the leaks "could" be the cause. but most tractors I have dealt with that have a problem, its all inside the case and the main piston seals you replaced already. Was the bore of the cylinder scored or damaged.

 

[Ben755]

Thanks for the inputs on this problem. The cylinder walls and the piston looked fine. The old seal was well worn and actually broken in one place. The jump was more
pronounced before I replaced the seal. The lift arms would fall about 1/2" and then jump back continuously after heat and pressure started to increase. Now, the jumps
are somewhat spasmodic - they start almost immediately, increases in frequency, then becomes occasional, and after maybe an hour, actually cease to occur. I considered
coating the cylinder wall with some Formula-8 thread dope in the hope of better seating and sealing the piston seal as I've read that junk has been used successfully in other
hydraulic seal problems. However, if this problem is in the control valve, I just may have to live with it. But, I do want to fix the line leak since it's causing about a pint
of fluid loss per hour.

 

[LD1]

Again, without seeing a hydraulic flow diagram of the tractor, the leak may indeed be causing your issue. A pint an hour is quite a bit for a small machine.

 

[kenmac]

banjo washers are the washers that are used. You can buy them an assortment at harbor freight if you ave one close. If not, try NAPA.

 

[normde2001]

Fix the leaks and eliminate them as a possible problem. A pint an hour is a lot of leak.

 

[clemsonfor]

yea the leak is the problem, I was not understanding this problem correctly. Yes if your loosing fluid out of the system it will have to fill it to maintain the height causing it to jump back up.

My valve looses fluid but does not leak externally. If I cut the tractor off the 3pt leaks down but if I close the lockout it stays up so the problem is in the valve. Its just worn, I have replaced all wear parts that I know of. I just live with it now, it use to bug me cause I wanted it all to be right but now I just live with it.

 

[careyo63]

I have a internal leak somewhere also IMO it 's a big one but I let it go with this. Mine will drop sitting not running. But also while it's running. It' lifts and I can lock it to keep it from falling so I just live with it. Yes I admit this is a Ghetto rig but it works so I don't have to lock it running. I noticed that my 3pt. handle would move forward, Downward even after replacing the tension bushing on the lift handle Assembly. Done all I could do to the Valve also. Look at my Tension Spring and it's applying pressure to the Valve at all times. But very little all the way down. So my thinking and it works for me is to IMO try and keep pressure Tight by the spring and see what happens. Every Nylon washer was worn slap out my tractor. Both the Throttle bushing was so brittle they fell out in pieces. I don't have a FEL so may not help what so ever. But try and make sure and keep pressure at all times on your Hyd. lift vale and a see what happens. Just using you thumb may test it doing it that way. In my Old Pic. I had of the 3pt. you can look at the handle almost all the way down-Forward but look at the spring is already expanding putting pressure on the Valve. Been like this for 8-9yrs.. But fix the leak also.... And of course The Hyd. Filter is clean to make sure that not giving you problems.