Posted by NCWayne on August 28, 2012 at 20:12:47 from (69.40.232.132):
In Reply to: Dynahoe 190-4 posted by Erich Boehm on August 28, 2012 at 06:41:38:
If it has a lock valve in the line , and the seal on the piston fails it will do exactly what you are talking about. I just repacked an outrigger cylinder on a customers bucket truck that was doing exactly what you are describing, and a bad piston seal was the culprit.
It can go down because there is more surface area on the back side of the piston than the rod side (due to the rod taking up space). As a result of the extra space the fluid going into the cylinder will pressurize it enough to push it down, and displace fluid from the rod end to the tail end. There is just enough pressure differentialgoing that direction to make it move out and displace the fluid past the piston. Going the other way, because of the different size area the pressure has less area on the rod end to act upon vs the tail end, and unfortunately the displacement of fluid, and lack of differential pressure, keeps it from building enough pressure to cause the lock valve to unlock and allow the cylinder to raise.
If you need to get it up you can break the lines loose and use a jack, another machine, etc to put pressure on the cylinder in the up direction. This should unlock the valve and allow the cylinder to rise with the applied pressure, but it will usually drop right back down when the pressure is taken off of it, but at least the cylinder is no longer pressurized and can be removed to be rebuild. Good luck.
We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]
Today's Featured Article - Hydraulics - Cylinder Anatomy - by Curtis von Fange. Let’s make one more addition to our series on hydraulics. I’ve noticed a few questions in the comment section that could pertain to hydraulic cylinders so I thought we could take a short look at this real workhorse of the circuit. Cylinders are the reason for the hydraulic circuit. They take the fluid power delivered from the pump and magically change it into mechanical power. There are many types of cylinders that one might run across on a farm scenario. Each one could take a chapter in
... [Read Article]
Latest Ad:
Looking 4 set 9 bolt hubs 3 1/8 inch to fit 60 to 4010 jd
[More Ads]
All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy
TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.