Top @ Tilt hydraulics

   / Top @ Tilt hydraulics #1  


Elite Member, Advertiser
Mar 19, 2005
4000\' mountains of Southern California
Mahindra 7520, Mahindra 3215HST, Case 580 extendahoe, Case 310 dozer, Parsons trencher, Cat D6,
I have a question regarding pilot operated check valves on T & T hydraulics. Why would you need these? If you install your new hydraulics with your new control valves, there should be no leakage. Or is there something that I am not understanding? I have T & T on my tractor without POCV's and I have not noticed them bleeding down. Is it just the size of my cylinders or have I just lucked out? I have looked at industrial tractors( Case, Ford, John Deere, Massey ) and none of them had them that I could tell.
The reason for asking is that I am in need of a smaller tractor and wanted to know why it was so highly recommended on the compacts and sub-compacts ? Just trying to get all my ducks in a row. /forums/images/graemlins/smile.gif
Thanks for any info.
   / Top @ Tilt hydraulics #2  
You have been lucky. As cylinders wear they often leak down. Sometimes they leak down because of tolerance stack. Most industrial tractors have more expensive valves that don't allow for leak down.
   / Top @ Tilt hydraulics
  • Thread Starter
JerryG, thanks, /forums/images/graemlins/smile.gif pretty simple. I will plan on installing with the POCV's. I am going to be on a tight budget this time around.
   / Top @ Tilt hydraulics #4  
Brian, I don't think the POCV is about leakdown. Of course it prevents that if the internal cylinder seals don't leak, but to me it's more about rigidity of position. If you don't have POCVs on your toplink and use it with a boxblade, don't you get some movement of the cylinder when you go from forward to reverse or when you first start to scrape and the load increases to the toplink? With the POCV, your cylinder will be rock solid. My first one was not solid, but my second one with POCVs is very solid. Notice that CCM's POCV is mounted right on the cylinder with short rigid hydraulic tubing. That's what eliminates the flex.
   / Top @ Tilt hydraulics #5  
Another thing to consider is the safety feature with the check valves mounted/plumbed on the cylinder. In the event of a hose rupture, your implement would not crash down. It would remain in position because of the check valves.

I know you're not supposed to work around or under raised implements but at times we all do it to some respect in order to get to the darn adjustments. Like if by chance you were working or adjusting and implent when it was raised and you, your hand or foot just happened to be under it when the line burst. Maybe like adjusting the scarifiers on the boxblade?

If the line burst while driving or operating, it would allow you to drive your tractor out of the field or wherever to your repair station without having to remove the implent or repair it on the spot where the line burst. Don't ask me how I know that one!
   / Top @ Tilt hydraulics #6  
For my uses on the farm, one spin of a regular threaded top link can make a world of adjustment difference to the various implements. I will at times use the same implement for several days - 20-30 hours of actual use. Once I get it set, I do _not_ want to have to fiddle with readjusting the top link.

Several of my 3pt implements are 20 feet or wider. I just don't even want a hyd side link - ick if that sags on me! A sprayer could be all messed up in calibration if one side sank a 1/2 inch........

Most hyd systems I have will leak down some. Normal wear & tear.

This whole issue is one reason I never seriously looked at a hyd top link.

Since I first read about poilot valves here on this site, I'm looking into giving someone a call for one now..... /forums/images/graemlins/smile.gif

My needs are heavier, & more critical, and many more hours of use than the average compact tractor user, so I understand where a 1/4 inch of movement over a couple hours doesn't matter to you, but over a week could cost me $5000 in corn...... /forums/images/graemlins/smile.gif I have enough things to pay close attention to, I don't need to babysit a top link that drifts on its own.

   / Top @ Tilt hydraulics
  • Thread Starter
Jim, I have not noticed any movement. That is not to say that it does not move, just that if it does it is such a small amount that it hasn't effected my work. My cylinders are 3 inch in diameter, so it takes a little more pressure to make them move. I was thinking this morning that if the piston seals were bad, that the pocv,s wouldn't help at all. So they really only eliminate flex from the hoses? /forums/images/graemlins/smirk.gif
Thanks for the info.
   / Top @ Tilt hydraulics
  • Thread Starter
rambler, I would have to agree with you in your circumstances 100%. If you are doing the same thing hour after hour and especially with those wide implements, you sure wouldn't want anything changing. But us guys doing stuff that is not so critical or costly and needing to adjust the 3ph sometimes every 20-30 seconds, (having to actually tilt left to right) I sure would hate to have to get off the tractor each time to do that. /forums/images/graemlins/shocked.gif
Thanks for your views /forums/images/graemlins/smile.gif.