The Fordson Tractor Pages Forum

Hi all. This is my first post about 1955 Major hydraulic pump even there is many topics about it.

My Major is suffering very weak lift of 3-point linkage since last spring. At this far I have changed:
- all O-rings of:
- valve assembly
- pipes
- hydraulic cylinder and pump.
- Filter is cleaned and oils changed, twice.

My next quess is pump itself. I tested pressure but I didn´t have "official" hydraulics gauge so I had to use preassure gauge for oxigen gas tank (up to 350 bar). Result was 0 bar without load and 60-70 bar with about 300 kg load. With 300kg load linkage was able raise only 10-20 cm.

Have any one tested only pump itself? I mean, just pump after it is removed from the tractor? Reason for this that I have pump on my garage and Major is 400km away, middle of nowhere

What parts of pump can be overhauled / repaired? At least O-rings, but what else?

I´ll disamble pump and try to share some pictures. But here is photo of her in real action

Welcome Major1955,

It's an easy job to dismantle the pump and check things inside. My geus is an o-ring break at the butterfly valve. You will recconise the butterfly valve.
And yes try to share some pictures.

Seals are used less than 10 hours.


0.05mm gap between gear and housing


0.3mm between gears


Nasty looking grooves....

I think measurements do not look bad but maybe scratches in pump body are too deep

The butterfly and other o-rings seems okay.
Sure looks bad. How many play has the gear studs in the bearing holes? If there's not much play, maybe it's the result of dirty oil scraping at the house.

Between housing and gear axle is less than 0.05mm.

Hpoe someone else can help you. Beats me.

Pressure relief valve leaking ?

Hi there,
Looking at the foto "nasty grooves" and at the area around the hole where the lower rotorshaft goes,it looks to me that a considrable wear has taken place increasing the "end clearance" of the rotor.I think that is where you are loosing pressure.
Kind Regard
svend.

SvendH wrote:Hi there,
Looking at the foto "nasty grooves" and at the area around the hole where the lower rotorshaft goes,it looks to me that a considrable wear has taken place increasing the "end clearance" of the rotor.I think that is where you are loosing pressure.
Kind Regard
svend.

Svend,
First of all, thanks for you opinion (also others too, of course). So you mean grooves on end bearing are causing preassure leakage? If not, please mark the spot you mean. Thanks!

Yes , by endbearing I mean the machined surface around the hole where the lower rotor-shaft should go looks erroded(in my opinion)Sorry about the arrow,no can do .You might be able to check the clearance with a straight-edge.

upload free



Pump shimmed. End bearings grinded and smoothed with 600 sandpaper and 0.5mm shim plate added. 150 bar pressure, but still wont lift. Next phase will be disassembling of top cover again. I'll post some photos about it soon

I think Oerick his tought might be the case.

Is the pressure varying with the engine speed ? i.e. when you rev up do you get more pressure ?? if not I would suspect the pressure relief valve as more revs to the pump should result in more pressure as the oil flow should increase in greater proportion to leakage in the pump mechanism whereas a failure of the PRV would tend to result in the pressure remaining the same or similar.

Was the tractor lifting Something when you measured 150 bar? Otherwise I dont See how it can build such pressere,are you sure the lift isent jammed somehow.

It will develop system pressure when the ram reaches the end of its travel Svend - that is the main purpose of the PRV, to shed the excess oil, limiting the maximum pressure the pump and its seals see. what I do not know is a method of testing the PRV other than by fitting another one

If PRV is open How can he measure 150 Bar? with that much pressure the hydraulicks would be labouring audibly i think

Glad you noticed that Svend - I was reading psi not BAR - looks like the PRV is doing it's job then, must be the lift valve, the ram or something blocked in between.

Are we certain it is bar and not psi?
1bar=14.6psi

SvendH wrote:Are we certain it is bar and not psi?
1bar=14.6psi

Bar-meter

SvendH wrote:Was the tractor lifting Something when you measured 150 bar? Otherwise I dont See how it can build such pressere,are you sure the lift isent jammed somehow.

Please see first picture. Pressure is measured directly from pump supply line. Valves are not involving measurement.

oehrick wrote:Is the pressure varying with the engine speed ? i.e. when you rev up do you get more pressure ?? if not I would suspect the pressure relief valve as more revs to the pump should result in more pressure as the oil flow should increase in greater proportion to leakage in the pump mechanism whereas a failure of the PRV would tend to result in the pressure remaining the same or similar.

Pressure directly from pump: idle about 100bar, from 1/2 engine speed to full-> 150bar.

Systen assembled:
No load: no pressure (any revs)
Load: no pressure at idle
about 70 bar at full speed

I've had a closer look at your test set up for the pump pressure, have you bolted a plate on so you can have a tapping for your test gauge pipe ? if this is the case then the block which the pressure relief valve is fitted is missing, in which case and by coincidence your maximum pressure developed at no flow is about the same as the normal system pressure )2000-2200 PSI or 135.6 - 149 BAR Despite your shimming and cleaning it may be that the pump wear is the root cause of your problem.

With the lift valve lever down oil cimply recirculates at virtually no pressure back into the back axle housing.

With the lift lever up and 70 bar measured it still indicates that you may have

PRV leaking
Other part of the oil / valve route leaking or not operating properly
Ram leaking
Ram or mechanism seized as with no implement on the lift arms I would expect some lifting motion.
Did you check when it was open that the piston can be moved ? if not block the arms in a high position and see if you can manually push the piston and with the arms released that it returns.

Or we are all missing a vital clue

Ram works with out load. Can lift load about 200kg with full engine revs.

With load, engine idle, lever up, no pressure. Engine with full revs, lever up, pressure about 70bar (max)

Okay, here comes the next part of story:

Picture 1.


Picture 2. Grinded with mating part


Picture 3.


Picture 4.


Picture 5.


Picture 6. How to check mating part of right side valve?


Picture 7.


Picture 8.

hi
I think you need to run a test of the pump itself "in tractor",ram and cover off,then fit an outlet pipe to the pump itself with handoperated "strangle-valve"+your preassure gauge.This should give you a realistic picture of the pumps capacity and perhaps remove some unknowns from the equation
This is only a procedure for the man who knows what he is doing !!

Correct me if I'm wrong, but on the cover of my Major is a connection for a user, direct from the pump. Red arrow on the picture. This could be a place to put a gauge.