A little help with 574 hydraulics

My 574 diesel lifts the three point "very" slowly with just a little weight on it (about 200 lbs.). It drops fine. With no weight it goes up and down fine. Here are some notes:
1. New hydraulic pump installed.
2. New main pressure relief valve.
3. New filter and very clean fluid.
4. Measure 1800+ psi at remotes.
5. Power steering works great.
6. PTO works great (runs a 7' bushog fine).
7. Rebuilt the MCV with new O rings and gasket.
8. Replaced O rings in unloading/flow control assembly.
9. The unloading/flow control valve moves freely in it's bore. No visable scoring.
10. Disassembled and cleaned the variable flow control valve.
11. Dead heading the remote in either direction causes the relief valve to squeal.
12. Replaced lift cylinder O ring and backup seal.
13. Disasembled and cleaned action control valve.

The only item not yet removed and checked is the seat for the unloading valve piston. The piston O ring has been replaced however.

I have been using the I&T Shop Service manual to troubleshoot and rebuild the hydraulics. Any suggestions here would be appreciated.

Firstly, hydraulic test at remotes needs to be done at about 1500 engine rpm and should show 2500psi

Secondly on the slow lift, what happens if you pull an auxiliary valve lever onto demand whilst lifting ??

My test at the remotes was at about 1200 RPM. I'll have to reassemble the unloading/flow control to rerun the test.
Pulling the remote lever up during the slow-lift issue had no effect. I did try that.
And thank you for the questions.

O/k rebuild and fit valve, then retesting pilling aux valve and let me know !!

Be sure no air leaks around the filter . My 584 had a canister cover which sealed to an o ring gasket. Had to take off and put back on several times before it sealed correctly and stopped aerating the hydraulic fluid. Oring has to be oiled and canister cannot turn while the bolt is being tightened.

Thank you Warren for the suggestion. I have read about that being a problem and been very careful to seat this cover correctly. Before breaking it down this last time the tractor ran for about 30 minutes after which I pulled the fluid dip stick which did not show any signs of cavitation. Before replacing the lift cylinder O ring cavitation was visable on the stick. I will check the filter cover again while putting the unload/flow control valve back on, perhaps this evening. Then I'll restest as cyrus suggested.

Was able to remove the unloading valve & seat this evening. The small shaft that inserts into the seat shows what seems to be very excessive wear. It will actually wobble in the seat. Will try to insert two pictures here.

Hi again

Looseness of the Unloader valve is not an issue as you say that dead ending the auxiliary valve has no effect on the slow lift!!

I think the issue lies elsewhere but ideally need the pressure test!!

Dead ending the aux valve during lift, rules out all problems in the Unloader and flow control valve assy if there is no change to rate of lift ??

While you have unit on the bench remove the union and check the flow control piston and its spring?? This piston (only) is matched to the valve body and could give slow lift, but if it was responsible for your issue the lift would speed up when the aux valve was dead ended!!

Okay, I have exactly 2500 psi at the remotes both cold and warm. That pressure holds even down to around 1100 RPM. I did not try it at any lower RPM. The pressure does not change when the three point is lifting. Dead heading the remote has no effect on the three point trying to lift. I also removed the filter cover and installed a new gasket. The one that came out looked good, no twists or damage.
After all of this the symptoms remain the same.

O/k good pressures!!

The thing that afects speed of lift is flow??

You say its o/k with no load on the links but is slow when you try to lift a small load??

Did you have the draft control valve out?? And if so i suspect the adjustments for spool travel may not be correct!!

Also i presume you are lifting using only the position control
lever( the inner one ) as when using the draft lever (outer one) the speed of lift is controlled by the raise responce valve setting (rear outer lever)"
In position control a sliding link pulls the raise respoce rotary spool to fast when the position lever is raised to full lift!!

To give me an idea of time, how many seconds does it take from fully lowered to fully raised, with no load and with alight load???

Yes, I am using the position control with the draft all the way down (forward) and the raise response in the fast (all the way up) position. And yes, the position control does force the raise response to the fast position if it is not already there.
I ran this by my local Case/IH dealer and the mechanic suggested measuring pressure at the unloading valve pressure input fitting. I did this and was able to read 2500 psi upon closing the restricter valve on my test setup. Also interesting is that while restricted, the three point lifted a 6.5 foot disk with no problem. Not sure if this is telling us anything of value or not.

With all lines connected normally and no three point load it will lift full height in about 3 to 4 seconds. With 200 lbs on the hitch it may not make the lift at all or at best it will take 20 seconds or so. This is with the engine at 1200 rpm.

The dealer mechanic is thinking the problem lies somewhere in the unloading valve assembly. Any thoughts?

The fault you have is not in the unloader & flow control valve as it is still there when u pull the aux valve lever to dead end the oil supply. At that point oil can only go 2 ways, to hitch cylinder to lift if draft valve is in lift mode , and to blow the main R/v and pass to return.

There is a problem with the linkages in the hydraulic top cover, it may be a circlip off or more likely the sensing beam and spring have become detached from their mounting pegs (hook end of spring may have broken off !! and as such the walking linkage has gone out of balance !!

To check, just rear of unloader &flow assy is a metal plate with the breather on it, remove this and you can see the linkage that operates the draft valve, operate the draft lever from full lower to full raise & back to lower again. (Engine stopped !!) and you should see the spring expand and contract. if it does then its a circlip issue, if it doesn't its a broken or detached spring.

Some skilled mechanics can replace spring through this plate but its very fiddly. Official way is hydraulic top off, replace, bleed brakes etc, allow about 12 hours labour.

I need your e mail so i can send document that shows the linkages!!

Also do you have a service manual ??

Just sent you my email address through this forum. I am using the I&T Shop Service manual which does show a good breakdown of the control linkages. I'll try the inspection you detailed sometime today.

Further to my last post !!!

Continue by staring the tractor and lifting 3 point hitch on the position control lever and gauge the amount of spool and lever movement!!

Then add your weight and lift again, comparing spool and lever travel (s) which should be the same!!

Do not!! At this time alter the spool adjustment and do not!! Attempt to adjust the drop check valve!!. The drop check appears to be correctly set !! The info from the I & T manuals on how these adjustments are done, appears strange ??? And not how we did them in the factory !!

Finally resolved this problem.
I decided to open the lift housing and remove the lift cylinder for examination. This is where I found a blown seal on the cylinder top which was likely caused by a loose mounting bolt. Hope the photo clearly shows this. After replacing these seals, reassembling, bleeding the brakes and testing, the lift works great. Nice smooth quick lift even at an engine idle. Many thanks to Cyrush for providing advice and some useful documents.