NAA - Hydraulics Unloader Valve

jrowen135

Member
This is a follow up to a lengthy thread that I posted before (https://forums.yesterdaystractors.com/viewtopic.php?t=1370640&postdays=0&postorder=asc&start=0)

Based on some suggestions that the unloader valve was stuck, I removed it. After removing, I re-inserted and drove back out numerous times, each time rotating the valve slightly just to check that it doesn't bind up in any way. I did not remove the bushing.

My main questions is: should there be a "flat area" as shown in the picture. There are three of these evenly spaced around the circumference. Just curious what the purpose of this would be.

My hope is that the unloader valve was stuck or partially stuck and that after re-assembly, I won't have the issue of having to remove the acorn nut and pushing in and out on the back pressure valve several times before the hydraulics start working.
mvphoto30136.png
 

"should there be a "flat area" as shown in the picture.". Yes, they are made like that. I won't speculate as to why. Designer is probably dead, so about all you can get are WAGs and speculation....sorry.
 

I am going to speculate the o-ring is the issue... If it breaks when you take it off no doubt the o-ring is bad... Did you replace it (o-ring)
 

I probably didn't choose my words the best there when I said "drove it out". It came out quite easily, just by inserting a punch by hand from the back end after inserting it all the way. Removing the valve the first time took a little more force but after that it was very easy, just with a slight drag due to the o-ring, which I thought felt normal and indicated a good seal.
 

The o-ring did not break when I removed the unloader valve, and appears to be in excellent condition the best I can tell. I was thinking about just keeping the same one on there, but have decided to get a replacement just for good measure.
 

It should not have a drag feel to it, it floats on the o-ring so I take it you did not replace it :( WHY you are not gonna get any closer to it...

The seal effect is pressure differential it dose not fit the description of sealing as in what you would normally take it to be... Its the way the engineer specked it tho not a normal way an o-ring works that's the way it is...
 

Remove it from the valve if it breaks its no good... If you are hardheaded and it does not break you can put it back on...
 
(quoted from post at 23:02:36 01/21/19)
Remove it from the valve if it breaks its no good... If you are hardheaded and it does not break you can put it back on...

Thanks Hobo! As I mentioned in the last post, I am going to replace the o-ring. I might be hardheaded, but not that much! :wink:
 

I have never been into a NAA if I had I could tell ya what size o-ring it took... I think I have read some used a metal split ring those that have BTDT know the deal... That being said unloaders that I have dealt with with a good o-ring shows know ware your o-ring does.

Be comfortable with what ever you use... A link in this post on a 640 unloader o-ring...



https://forums.yesterdaystractors.com/viewtopic.php?t=1335637&highlight=unloader
 

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