Hydraulics bobbing when anything of 3 pt lift

[Livewire84]

I have a 62 super major, but I swear it looks like a power major hydraulic top.
I am not sure if thats possible, but I dont have all the tipping valves, or remote valve, or any of that.
Just a blank plate, blocking that area off.
I have the old style pressure relief valve in the front, behind the big bolt head, that sits almost flush.
I have rebuilt and re oring the pump, re oring the entire lift top, including the ram cylinder, checked the feed tube for cracks, installed new exhaust filter, changed rear end oil and cleaned the mesh screen. I cannot figure out why this crazy thing bobs up and down, when anything is attached to the 3 point lift arms.
Doesnt matter is it is a 100 lb lifting boom, 400 finish mower a really heavy set of disc.
It will lift the weight, no problem, after having my pump machined, but if I lift in draft control setting, it will slowly bleed all the way down, even though the handle is at the top.
If I lift in position control, it will correct itself constantly, but hold the load up.
If I shut the tractor off with the load lifted, it does bleed down.
The one thing I did notice is the ball in the non return valve, which I believe is also the old style, that is accessible from the outside of the lift top, looks like it has a indention of the seat it is supposed to be mating to.
How in the world would a ball bearing get scored the same shape as the seat ?
Could this be causing the fluid to leak / flow past that sealing ball / seat and be causing my problem ?
Any advice is greatly appreciated !

[SvendH]

Jo there
In my opinion first thing to check for would be a blown O-ring on one of the sealing plugs under the lift top

[Livewire84]

What do you mean by sealing plugs ?
I do not understand what part that is, by the name.
I am pretty confident that all my orings are good, as the tractor was doing this bobbing thing, before all new orings and work metioned above.
The problem that led me to rebuild the entire lift top, and have the pump machined / rebuilt was it kept blowing orings.
There was too much play in the pump, and it would blow out a set of pump orings in about 10 hours or so. After replacing 2 sets, I rebuilt the top and pump.
The pressure relief valve works and actually kicks out to soon, according to my pressure gauge.
I need to shim it, a tad, but for now am leaving it alone.
I have since used the tractor, and lift seems strong, but bobs with a load, no matter the weight.

[oehrick]

Reference the non return valve, after a while the oil becomes abrasive with the much and rust it accumulates (you may have just corrected this in the pump!) so may account for the ball and seat wearing, there is also 60 years of hammering as the ball seats to consider, while hardened the 'rivetting' effect can do this.

The bobbing is natural due to leakage in the system and in one of the manuals it mentions this and a number of times a minute which could be considered 'normal', a weeping valve or O ring could result in the increased leakage - it will be between the lift valve 'correcting valve' and ram as other than when it is lifted by the 'bob' the pump circuit is not under load when the lift valve is not being operated.

The other possibility is the ram seal (if worn or nicked) or cylinder (if scored or pitted) weeping oil

If you replace the check valve ball, make sure to get the same size within a thou or so, it is traditional to get two, the first you whack into the seating using a brass drift (same size as the inside of the housing to ensure it hits square) to take tiny errors out of the seat, otherwise it needs re machining and then put the second ball in for service as the first one can be distorted by the wallop. I have superglued a ball on a bit of thin tube, covered it in black magic marker then wiggled it against the seat (don't rotate it) low spots show by the marking staying put, bright where it touches.

Happy hunting

[Livewire84]

That is exactly the guidance I was looking for.
Now the hard part seems to be, to find a ball that exact size !
Thank you for the advice !

[oehrick]

Any supplier of ball race bearings ought to be able to supply single balls to a specified size, although a minimum order charge may not make that cheap

Not sure if any of the tractor supplies people do them but it might be worth contacting your local New Holland tractor dealer as they claim to be the successors to Ford and Fordson and do quite a bit of sponsorship for events in the UK and buying bearings by the ton minimum order from the makers or factors shouldn't be a problem.