Pressure drop normal?

[rd_macgregor]

For the first five or six years of my tractor's life, the hydraulics held their pressure/positions. However, I noticed recently that the lower 3PH arms now sink all the way down after being parked for a week. Is this normal, or a harbinger of repair work to come?
Bob

 

[LD1]

Sounds fine to me. Is that with or without an implement on the back??


Unless it drops to the ground at a noticeable rate, I wouldnt be concerned with taking a week to bleed off.

 

[rd_macgregor]

That's without an implement. Just the bare 3PH arms. It isn't a rapid change, but the system always used to hold pressure, with no appreciable drop, for much longer. I guess it doesn't hurt anything, since the arms come right back up to whatever level they are set at when I start the tractor again. I just want to be sure this doesn't suggest some bigger issue is developing.
Bob

 

[k0ua]

Think of it this way, all spool valves have to have some clearance or they could not move in their bores. Clearance equals leakage. Some small amount of fluid will always leak by. As the valves wear over time that leakage will increase.. But a leakdown of the 3pt in a week or even a couple of days is still darn good.. When you should get worried is when you can watch it drop and the position control "bumps" it back up. That is bad. Somewhere in between is an "acceptable" amount of leakage. You will have to determine what is acceptable.

James K0UA

 

[LD1]

Just normal wear and breaking in of the internal cylinder and valve.

Try putting an implement on it. Say ~500lbs. If it holds it up for an hour or more, things are fine.

If it drops to the ground within minutes of shutting off the tractor, then you have issues.

 

[Zebrafive]

My JD 2030 3pt drops in minutes after shutdown, but stay up when running, so I do not worry about it. Been years since it held for a week shut off, but it's 39 years old to.

 

[J_J]

Install a hyd pressure gage in the hyd system, and see if the relief valve comes on when using the loader or the 3pt.

That will give you a relative health of the hyd system.

If the relief does not come on when using the 3pt, that probably means that the fluid is bypassing the cyl seals, or you do have enough load to develop the pressure. If yo can raise the lever and the cyl can go to max and the relief comes on, that should be good enough.

As seals age, ;they harden up and can not do the job they once did.

Some leak down is to be expected, and it will be your experience whether you can accept what is.

Some people want perfect and others want OK, and others use what is, accepting the loss.

Static leak down is where an implement is pulling on something and adding weight to the holding capacity of a closed cyl.

The valve could be leaking also, causing fluid to be pulled past the spool and the bore of the valve.

 

[LD1]

My JD 2030 3pt drops in minutes after shutdown, but stay up when running, so I do not worry about it. Been years since it held for a week shut off, but it's 39 years old to.

Yep. You likely have a leaky valve or leaky cylinder. Live hydraulics is what holds it up when running.

Honestly, most people probably dont even know how long before their 3PH drops. Cause if my tractor is off, the implement is on the ground. And while running, live hydraulics do the work.

Not the case on the 8N though.....Those leak down pretty good, especially with warm oil. And PTO has to be running to raise/lower. Kinda a PITA for a bushhog or tiller

 

[SPYDERLK]

My 2010 JD will often stay up "forever" when it has a heavy implement on, but will regularly leak down slowly [a few hrs] with no or light load. Many seals "self energize" under pressure and can form a better seal in those cases.

 

[Utopia Texas]

Every tractor I own has a levered valve near the seat that determines how slow a implement drops when the hydraulic lever is moved forward. Check if your unit has such a lever to see if it has accidentally been moved a bit. I do not know what it is called but in one direction it allows the rear arms to drop very fast and in the other direction it can lock the arms in the up position where they will not go down. I believe the valve is used to compensate for different implement weights.