All of a sudden my loader started leaking down under load.I had the bucket cylinders rebuilt and took control valve apart but there is really nothing there but 2 spools and i guess relief valve.The back part of my tractor works great.The back will haul the brush hog in the air all day.But the curling of the bucket doesn't.It will just start dropping quickly.The arms work great.They will stay up no matter what.Evidently the pump is not the issue.It was a hydraulic repair shop that rebuilt cylinders but that really doesn't mean anything.Anyone else ever had this issue or knows whats wrong with it?:confused2:
New Holland 7308 loader problem
- Thread starter racer86y
- Start date
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RNeumann
Elite Member
Curl the bucket and disconnect the curl hydraulic lines at the QDs.....if you have QDs. Otherwise you will need caps. Then see if it still drifts. That will point to the valve or cylinders.
Btw- if you use caps be sure to use a ratchet strap or chain to hold the bucket while the lines are open/un-capped.
Btw- if you use caps be sure to use a ratchet strap or chain to hold the bucket while the lines are open/un-capped.
RNeumann
Elite Member
Yes sir
:cool2:
oldnslo
Super Member
Not to insult your knowledge but I doubt that you pulled the correct QD,s for the bucket. Trace both hoses from the curl cylinder back to the valve. If they are both pulled and the bucket doesn稚 dump then it would point towards the directional valve leaking. This can be caused by the valve not centering properly or a scored spool and body.
I traced the lines a long time ago.Bucket lines are the 2 on the right and boom lines are 2 on the left.Control valve is 800 bucks so i wanna make sure thats what it is before i throw that much at it.I bought another control valve for it and it did the same thing.Would the relief valve cause the bucket to uncurl and boom to stay?The control valve was not new either,it was 200 bucks.I took it off and sold it and put original one back on
oldnslo
Super Member
Racer
The main system relief would not allow the loader to drift with the spool in the spring center position. The spool would isolate the relief from the relief.
With both hoses disconnected there is No path for the oil to get to the valve so that is why I questioned both hoses being disconnected.
Have you tried swapping the lift lower hoses to the curl dump to see if the lift lower now holds or drifts & curl dump to lift to see if it holds position
The main system relief would not allow the loader to drift with the spool in the spring center position. The spool would isolate the relief from the relief.
With both hoses disconnected there is No path for the oil to get to the valve so that is why I questioned both hoses being disconnected.
Have you tried swapping the lift lower hoses to the curl dump to see if the lift lower now holds or drifts & curl dump to lift to see if it holds position
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RNeumann
Elite Member
Two valves that are both doing the same thing? Probably not the valve. How is the relief valve plumbed into the system? Is it a part of the loader control valve or a separate piece?
It is part of the control valve.Right beside the 2 spools
RNeumann
Elite Member
If the valve included the pressure relief and you have switched that I’d say that isn’t the issue. The issue is between the lines and the cylinders. If it didn’t leak down with all 4 unplugged but did with 2 unplugged I’d start unplugging 1 at a time. Isolate the issue.
Yes sir.I will do it.This afternoon i am gonna figure it out.Cylinders have been rebuilt but we all know how that goes....lol
:confused2:I am giving up on this.I don't have high dollar guages etc...just gonna take it to New Holland and let them rip me a new one
RNeumann
Elite Member
LD1
Epic Contributor
This isnt rocket science and I wouldnt jump too soon on taking it in.
There are basically only THREE things that can cause the bucket to leak.
But before we get into that, I would first question the timing. You say it bleeds down (bucket dumps itself) under load. HOW LONG does this take to happen? Matter of seconds? Minutes? Hours? Overnight?
ALL spool valves will leak "some". Because there are no "seals". Its simply a very precisely machined steel spool that fits into a cast iron body. With tolerances measured in tenths of a thousands of an inch. 0.0001" Valve manufactures usually have a specification of acceptable "leakage" rate in mL or ounces of fluid in a given time at a given pressure. Since pressure and cylinder volume can be figured.....this translates to the tractor manufacture in inches per hour. The tractor manufacture "should" have a specification......maybe 6" per hour or something. Anything less is deemed "acceptable".
SO......HOW FAST or HOW LONG does it take to leak down, and under what kind of load?
Now on to the THREE things that can cause your bucket to "uncurl" itself.
1. Leaking hydraulic oil somewhere EXTERNAL. Leaking hose, leaky fitting, etc. Are you leaking oil anywhere visible?
2. Cylinders need replaced or rebuilt. IF you have bad seals or a scored up cylinder wall, fluid can bypass as the rod extends (dumps the bucket).
3. Oil is leaking back PAST the metal-metal "sealing" area in the spool valve.
In a properly functioning system, and the control valve in the neutral position, the hydraulic oil is trapped in the cylinder and has NOWHERE to go. The spool valve (joystick control valve) SHUTS OFF the hoses from the rest of the system preventing oil movement, and thus preventing physical movement.
UNHOOKING the TWO QD's that are for the DUMP only.....does the SAME thing. Since the QD's when unhooked act as if you just capped the hoses.
But by unhooking them, you SEPARATE the cylinders from the valve.
With them unhooked, if the drift/bleed down still continues, you know that it CANNOT be the valve. Because the valve has been DISCONNECTED from the cylinders. And the ONLY thing left to be happening is oil is bleeding past the piston in the cylinder, either because if bad seals or a scored cylinder wall.
With them unhooked if the drift/bleed down no longer happens.....you have just proven that there is NOTHING wrong with the cylinders. And the only thing left that would cause the drift if leaking past the spool when the hoses/QD's are connected. IE: bad valve.
you do NOT need fancy or expensive gauges to trouble shoot this problem. And if you take it to the dealer, they are going to do the same thing I have described to determine if the valve or the cylinders are the culprit.
The ONLY other thing to check is to make sure that the valve joystick is ACTUALLY returning to neutral. Make sure there isnt a mechanical bind, or a cable sticking (if cable operated) preventing the joystick from returning all the way to neutral.
There are basically only THREE things that can cause the bucket to leak.
But before we get into that, I would first question the timing. You say it bleeds down (bucket dumps itself) under load. HOW LONG does this take to happen? Matter of seconds? Minutes? Hours? Overnight?
ALL spool valves will leak "some". Because there are no "seals". Its simply a very precisely machined steel spool that fits into a cast iron body. With tolerances measured in tenths of a thousands of an inch. 0.0001" Valve manufactures usually have a specification of acceptable "leakage" rate in mL or ounces of fluid in a given time at a given pressure. Since pressure and cylinder volume can be figured.....this translates to the tractor manufacture in inches per hour. The tractor manufacture "should" have a specification......maybe 6" per hour or something. Anything less is deemed "acceptable".
SO......HOW FAST or HOW LONG does it take to leak down, and under what kind of load?
Now on to the THREE things that can cause your bucket to "uncurl" itself.
1. Leaking hydraulic oil somewhere EXTERNAL. Leaking hose, leaky fitting, etc. Are you leaking oil anywhere visible?
2. Cylinders need replaced or rebuilt. IF you have bad seals or a scored up cylinder wall, fluid can bypass as the rod extends (dumps the bucket).
3. Oil is leaking back PAST the metal-metal "sealing" area in the spool valve.
In a properly functioning system, and the control valve in the neutral position, the hydraulic oil is trapped in the cylinder and has NOWHERE to go. The spool valve (joystick control valve) SHUTS OFF the hoses from the rest of the system preventing oil movement, and thus preventing physical movement.
UNHOOKING the TWO QD's that are for the DUMP only.....does the SAME thing. Since the QD's when unhooked act as if you just capped the hoses.
But by unhooking them, you SEPARATE the cylinders from the valve.
With them unhooked, if the drift/bleed down still continues, you know that it CANNOT be the valve. Because the valve has been DISCONNECTED from the cylinders. And the ONLY thing left to be happening is oil is bleeding past the piston in the cylinder, either because if bad seals or a scored cylinder wall.
With them unhooked if the drift/bleed down no longer happens.....you have just proven that there is NOTHING wrong with the cylinders. And the only thing left that would cause the drift if leaking past the spool when the hoses/QD's are connected. IE: bad valve.
you do NOT need fancy or expensive gauges to trouble shoot this problem. And if you take it to the dealer, they are going to do the same thing I have described to determine if the valve or the cylinders are the culprit.
The ONLY other thing to check is to make sure that the valve joystick is ACTUALLY returning to neutral. Make sure there isnt a mechanical bind, or a cable sticking (if cable operated) preventing the joystick from returning all the way to neutral.
I have the guage but cant find the right qd's
