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?
New Holland 7308 loader problem
- Thread starter racer86y
- Start date
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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
