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dclifton 
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Joined: 19 Nov 2016
Location: Tyler Tx
Points: 19
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 Topic: HD11EC hydraulics question
Posted: 27 Jan 2018 at 6:11pm |
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Ok I have an HD11EC with the front hydraulic tank and pump unit. There is not much on this thing I haven’t had apart or rebuilt. I have a problem that has just started in the last few weeks dozer only gets ran a few hours a week around the farm. It’s just a Rake Dozer for us.
The blade has pressure down and will pick the front of Dozer off the ground. But it will not raise the blade back up. You can let it sit for several hours and go back and it will work a bit then all of the sudden it won’t pick up the blade again.
Any of you run into this?
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DMiller
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Joined: 14 Sep 2009
Location: Hermann, Mo
Points: 30736
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Posted: 28 Jan 2018 at 6:22am |
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If control spools are working and sliding properly I would look into getting it where you can perform a few tasks and not be blocked or blocking or having to consistently travel to and from it. First off does it have rapid down release system in the cylinders? If not follow below.
Will need a at least one high pressure hydraulic gauge, at least 5000# for a buffer. On either blade cylinder remove the feed line for lift, attach the gauge CAP the port on the cylinder(I take old fittings and weld the hose end shut), have someone else move the control to lift. Pressure should rise steadily as the person moves the lever slowly, if not then move to the other cylinder and perform again. If neither will show a pressure rise, leave the gauge on the second cylinder hose, cap ALL the other lines to the cylinders(both) and retry. This will rule out the bypass valve inside the cylinder as allowing the pressure to feed from one side to the other(my 7G is weak here). Can either be the bypass over pressure protection in one or both cylinders or the seals in a cylinder are shot but will seal up when reverse pressure applied. If you do not cap the cylinder fitting and the seals are bad it will shoot hydraulic fluid like a fire hose on a cross feed.
If that last test still shows no pressure you have a control body issue.
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dclifton
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Joined: 19 Nov 2016
Location: Tyler Tx
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Posted: 28 Jan 2018 at 8:35am |
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This is exactly what I was going to try next. I’m in the hydraulic business so I’m pretty familiar what systems and the concept but this old pump is kinda antiquated compared to today.
I just had the cylinders rebuilt a month or 2 ago. Makes me wonder if I have a bypass issue in the cylinder since this really started after the cylinders where rebuilt. We contract out all of our cylinder rebuilds to another shop. Generally we have zero issues with there work but this one has me wondering. I will try the pressure test on the cylinders.
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DMiller
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Joined: 14 Sep 2009
Location: Hermann, Mo
Points: 30736
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Posted: 28 Jan 2018 at 1:10pm |
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Try to post a photo of your cylinder arrangement, Allis had cylinders equipped with a rapid down system and they work differently, I have not been inside of one of those or tested anything similar.
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dclifton
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Location: Tyler Tx
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Posted: 28 Jan 2018 at 7:53pm |
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I already got it figured out after some process of elimination I figured out that the cylinder shop didn’t get the washers, spacers and plates that float back and goth to activate the check valves aligned. This was causing them to stick open one way. After I messed with it a few mins one I pulled it out I understood how it worked and was able to put it together correctly.
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dclifton
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Posted: 28 Jan 2018 at 7:54pm |
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Just of curiosity what is the rapid down system?
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Ian Beale
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Joined: 03 Oct 2011
Location: New South Wales
Points: 960
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Posted: 28 Jan 2018 at 11:34pm |
 dclifton wrote:
Just of curiosity what is the rapid down system? |
I'm presuming it would be like the quick drop valvery on our FA 10. If you move the blade control gently towards down it sends the oil back through the plumbing and the main control valve and the blade comes down slowly. If you go more energetically on the control it activates valves that shunt the oil from bottom of cylinder direct to top and the blade drops quickly. I've built a frame for changing rusted on grader tyres that uses this feature as the hammer.
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