Valve leak down

[J_J]

No, I don't think the oil has anything to do with the leaking down. They apparently used valves with a certain tolerance, maybe because they were a good deal. The oil gets thinner as it gets hot. As far as the pressure, that wouldn't change much. Some of the hydraulic hoses have a burst pressure of 3 times the pressure stated on the hose.

 

[J_J]

No, I don't think the oil has anything to do with the leaking down. They apparently used valves with a certain tolerance, maybe because they were a good deal. The oil gets thinner as it gets hot. As far as the pressure, that wouldn't change much. Some of the hydraulic hoses have a burst pressure of 3 times the pressure stated on the hose.

 

[MossRoad]

Yes, and if you put something with more weight on it than the bucket, like the brush hog, the leak down is much faster. This brings up a safety point about tractors and implements... we've always been taught to never get off a tractor with a 3pt implement raised. Same thing for snow plows on pickup trucks. I know many of us do it anyway, don't we? I clean the mower deck this way... but I use a garden hoe upside down to scrape it off and never actually get my body under the implement. Even if the valves had zero leak-down, I would not trust them.

Now back to our valve discussion... /forums/images/graemlins/grin.gif

What type of valves did you use on your backhoe, J_J?

 

[MossRoad]

Yes, and if you put something with more weight on it than the bucket, like the brush hog, the leak down is much faster. This brings up a safety point about tractors and implements... we've always been taught to never get off a tractor with a 3pt implement raised. Same thing for snow plows on pickup trucks. I know many of us do it anyway, don't we? I clean the mower deck this way... but I use a garden hoe upside down to scrape it off and never actually get my body under the implement. Even if the valves had zero leak-down, I would not trust them.

Now back to our valve discussion... /forums/images/graemlins/grin.gif

What type of valves did you use on your backhoe, J_J?

 

[J_J]

About the only time that people suspect their cylinders are leaking is when you see the oil on the outside. There is a test that you can do to determine if the cylinder is leaking on the inside. Do not get under the lifting arms when doing this test. Raise the arms up, remove the hydraulic line from the fitting close to the shaft end, this side is not pressurized at this time. A little fluid will come out when you take the line off. What you are doing here is that you have applied pressure to the bottom of the cylinder, which pushed the shaft out. On the other side of the plunger which the shaft is attached, no oil is being forced into the cylinder. If a good amount of oil comes out of that cylinder hole that you removed the line, then that cylinder is leaking. I have rebuilt all three of my hydraulic cylinders, with the cylinder rebuild kits from PT. My lift arms still drop, more so with a load. On some of the PT's, one of the PT members mentioned that you could see the lift arms move. It may leak on the up stroke and not on the down stroke. Just use good common sense and know where the pressure is and what it is supposed to do. I also have a quick connect hyd fitting in some of my hydraulic lines, and just plug in the 5000 psi gage to check the pressure.

 

[J_J]

About the only time that people suspect their cylinders are leaking is when you see the oil on the outside. There is a test that you can do to determine if the cylinder is leaking on the inside. Do not get under the lifting arms when doing this test. Raise the arms up, remove the hydraulic line from the fitting close to the shaft end, this side is not pressurized at this time. A little fluid will come out when you take the line off. What you are doing here is that you have applied pressure to the bottom of the cylinder, which pushed the shaft out. On the other side of the plunger which the shaft is attached, no oil is being forced into the cylinder. If a good amount of oil comes out of that cylinder hole that you removed the line, then that cylinder is leaking. I have rebuilt all three of my hydraulic cylinders, with the cylinder rebuild kits from PT. My lift arms still drop, more so with a load. On some of the PT's, one of the PT members mentioned that you could see the lift arms move. It may leak on the up stroke and not on the down stroke. Just use good common sense and know where the pressure is and what it is supposed to do. I also have a quick connect hyd fitting in some of my hydraulic lines, and just plug in the 5000 psi gage to check the pressure.

 

[Spiffy]

Whether the leak down happens over minutes hours or weeks, I don't see any difference in safety. The only thing I can think of is they were trying to save a few dollars.

I have a couple Farmhand loaders, each over 30 years old, one more like 50 years probably. The cylinders have finally started to leak slightly [I don't think the valves are leaking at all], but even at that they'll hold for days. The PT: maybe hours - with the cylinders that appear to be holding (I haven't checked for internall leaks). /forums/images/graemlins/frown.gif Minutes with the weight of the tractor on it.

 

[Spiffy]

Whether the leak down happens over minutes hours or weeks, I don't see any difference in safety. The only thing I can think of is they were trying to save a few dollars.

I have a couple Farmhand loaders, each over 30 years old, one more like 50 years probably. The cylinders have finally started to leak slightly [I don't think the valves are leaking at all], but even at that they'll hold for days. The PT: maybe hours - with the cylinders that appear to be holding (I haven't checked for internall leaks). /forums/images/graemlins/frown.gif Minutes with the weight of the tractor on it.

 

[J_J]

I can't remember that valve name right now. I will look and maybe take some pictures tomorrow. One thing to remember on your valve selection, is that the vender or salesman will tell you that all valves will leak down. some more than others You just hope that you get one with tight tolerances. Even if they do leak down,or you are using old or worn valves, check valves will satisfy most conditions. I think they call them load checks. If you can get some valves with built in load checks, that is the way to go. Were you going with two joystick setup, or a 6 bank of valves.

 

[J_J]

I can't remember that valve name right now. I will look and maybe take some pictures tomorrow. One thing to remember on your valve selection, is that the vender or salesman will tell you that all valves will leak down. some more than others You just hope that you get one with tight tolerances. Even if they do leak down,or you are using old or worn valves, check valves will satisfy most conditions. I think they call them load checks. If you can get some valves with built in load checks, that is the way to go. Were you going with two joystick setup, or a 6 bank of valves.