8N Hydraulics - Help Please

Hi all,

Long time lurker, first time posting.

I first off want to thank a lot of guys on here that have helped me troubleshoot my dads 8N. Dell, Soundguy, Bruce, Zane, there are others too I cant think of, but I really appreciate all the help.

Working on my uncles 8N. Two weeks ago we did my Dads 8N. It had the normal piston leak, and lift would not go all the way up. Replaced the cam follower pin, and a new NAA piston fixed it right up. My uncle mentioned his lift was weak too. It will lift all the way up but with a wood splitter on it, you have to crank the rpms to get it to lift, and once it is all the way up if you press the clutch it drops to the ground in seconds. He mentioned it came on quickly, was not a gradual issue that got worse over time.

Heres what Ive checked so far:

1. Hydraulic lift cylinder is not leaking. He converted it to a NAA style a few years ago.
2. No leaks from the top plate or anywhere up high. Top cover gasket is not leaking.
3. Pressure relief valve does not appear to be leaking by. It is not original, it has multiple holes in the sides. But when the pump is running I cannot feel any fluid coming out of it. There is no obvious movement in the oil.
4. On thing I did notice was a layer of foam on top of the oil. The oil itself was not creamy looking so water didnt appear to be an issue.

At this point I figured it was in the pump or I was hoping the bottom gasket was blown near the tube perhaps. The pump was moving, nothing appeared to be broken.

Today first thing I did was remove the relief valve and double check it to see if it had dirt in it. Appeared to be fine.

Next we drained oil and dropped the pump. The bottom gasket was old, but didnt show an obvious bad spot.

We took the pump apart, cleaned all the sludge out and put new gaskets on the valve chambers. The old gaskets didnt appear to be bad.

The valve seats did have some wear. I wonder if this is our issue, but will keep going here.

The pistons are worn. One in particular had a big groove in it, as did the housing in the valve chamber. Must have had something get in it at some point.

Reassembled everything and put new oil in it, traveller all mineral sae90.

Fired it up and pretty much have the same issue. Heres where I need help. When its running I see no bubbles or air in the oil, but as soon as I turn the key off, it starts to roll foamy oil up in the upper right corner near the transmission. Not around the tube more against the transmission housing. And nothing in the center of the pump near the pistons. Is it possible the valve seat are not holding and due to one of the pistons being scarred, its somehow getting air in the oil? This is where Im not sure and I havent seen a similar issue posted. Before we pull the trigger on a complete rebuild kit I wanted to ask the 8N experts. The tube doesnt appear to be split, I would think it would be blowing out oil while running, not after shutting down. Same result with a cracked housing I suspect.

I am going to try to post a picture of the foamy oil coming up after we shut it off. I also have a video of it, not sure if I can post it. The iPhone can really see what is going on in there, pretty handy.

Thank you for any insight anyone may have!

Donnie
 
Not having any luck posting the picture. Any ideas? Trying to post from my phone. Ive resized it but it says my post has words that violate the forum rules?
 
Worn pump pistons/bores will not result in leak down after shut off, for as you can see in diagram, those are isolated from ram by the check valve. The exhaust valve is not isolated by check, so it is a possible leak point along with all the others marked.
2jQjBgv.jpg
 
Thanks for the diagram JMOR, thats helpful.

I did notice the exhaust control valve was pitted. But if it was bad, would it be bubbling up oil all the time, even when running? The interesting part is I dont see the air entrained oil come up until I shut the key off. And it shows up in the northeast corner near the transmission.

Is it possible the check valve on the end of the pressure relief valve is bad? It is open while running, but when pump is off, could it allow oil back through the valve seat and out through the piston if its bad, thus releasing the air entrained oil?


Thanks,

Donnie
 
check open while lifting. Yes to leak back question.
If exhaust, I would expect that leak to be present anytime pressure is in circuit, both lifting and holding.
 
Can you message me your email address if you are willing? I cant seem to get a pic or video posted.

Thanks,

Donnie
 
Trying this again.


[video play=false:2d67751e2e]https://forums.yesterdaystractors.com/videos/mvvideo58668.mp4[/video:2d67751e2e]
 
Not sure how to get a video loaded. It's less than 2MB, and I've tried .avi and .mp4. Also made sure the name didn't have any spaces or special characters.

Basically the oil is clear and clean until I turn it off, then the air entrained oil comes rolling up, next to the transmission, in the upper right corner.


Donnie
 
(quoted from post at 21:11:35 07/18/20) Not sure how to get a video loaded. It's less than 2MB, and I've tried .avi and .mp4. Also made sure the name didn't have any spaces or special characters.

Basically the oil is clear and clean until I turn it off, then the air entrained oil comes rolling up, next to the transmission, in the upper right corner.


Donnie

Upload your video to YouTube. The will convert it to a streaming format and you can then post a [b:63e50e1db2]LINK[/b:63e50e1db2] to it.

Your description of the leak sounds a lot like a ruptured pressure tube .

TOH
 
(quoted from post at 08:33:57 07/19/20) https://youtu.be/ep7oTv67mW0

Thanks TOH. Link to video above.
efore video, I would have said same as TOH, but that source looks well away & fwd of the tube? I can't think of anything up that way unless cracked housing or some pathway around gasket?
 
Yea its strange to me. If it was a valve chamber gasket would it not be leaking while under pressure all the time? And I did put new gaskets on. This shows up like something is draining backwards after the pump stops. Unless it is an unrelated issue with the transmission perhaps? But got to believe it is part of the leakdown. That video is with no load on the lift arms, just raised up all the way. I guess I can check to see if I get the same result by pushing the clutch in without shutting the tractor off.
 
Thinking that it could still be at base of vertical tube, I might lower the oil level, for better view, to see if it may be squirting forward from base of tube and hitting forward wall before coming to surface. If load on three point you might be able to lift load, stop engine, reach in and feel for leak.
 
(quoted from post at 11:16:19 07/19/20) Thinking that it could still be at base of vertical tube, I might lower the oil level, for better view, to see if it may be squirting forward from base of tube and hitting forward wall before coming to surface. If load on three point you might be able to lift load, stop engine, reach in and feel for leak.
here is nothing pressurized in this area (circled). I suppose that if you have this much sludge, oil could tunnel under it toward front?
ngAYDkm.jpg
 
(quoted from post at 21:16:19 07/19/20) Thinking that it could still be at base of vertical tube, I might lower the oil level, for better view, to see if it may be squirting forward from base of tube and hitting forward wall before coming to surface. If load on three point you might be able to lift load, stop engine, reach in and feel for leak.

My thoughts also : )...

I don't want to muddy the water I don't believe his unusual bubbles problem has a thing to do with the relief valve other than to say I have never been able to see swirling are bubbles come from a know bad relief valve as has been posted as a way to check it. I have never been able to feel it either so keep your paws out of the sump!while the PTO is engaged...

As far as taking the relief valve apart I have had bad ones That looked great... I put a new on in it and move on : )

This one is gonna be interesting I am looking forward to the fix...

Thank you JMOR for the nice work you do : )
 
(quoted from post at 14:30:04 07/19/20)
(quoted from post at 21:16:19 07/19/20) Thinking that it could still be at base of vertical tube, I might lower the oil level, for better view, to see if it may be squirting forward from base of tube and hitting forward wall before coming to surface. If load on three point you might be able to lift load, stop engine, reach in and feel for leak.

My thoughts also : )...

I don't want to muddy the water I don't believe his unusual bubbles problem has a thing to do with the relief valve other than to say I have never been able to see swirling are bubbles come from a know bad relief valve as has been posted as a way to check it. I have never been able to feel it either so keep your paws out of the sump!while the PTO is engaged...

As far as taking the relief valve apart I have had bad ones That looked great... I put a new on in it and move on : )

This one is gonna be interesting I am looking forward to the fix...

Thank you JMOR for the nice work you do : )
ot to make this 'mutual admiration day', but Hobo, I always look to see what you have to say..............the man with his hands in it every day.
 
Thank you Hobo and JMOR.

You guys are exactly right. The bubbly oil is coming from the transmission. I disengaged the PTO while running and got no bubbles. Turned tractor off and bubbles appear. Checked transmission and see lots of bubbles in it. So unrelated for sure. Any ideas on that?

I will try the relief valve next, easy to try without pulling the pump. Will post results.

Thank you guys, really appreciate the help!!!


Donnie
 

That's why I did not want to muddy the water forget what I said... Al-tho the relief valve may be an issue its safe to say that's not the issue with the bubbles nor is it with the transmission... Stay on JMOR's game plan drain it down for a better look... You can also blow compressed air into the test port...

Your problem is unique we are all itching to see the outcome don't wonder about stay with the game plan... : )
 
Will do. Agree it may be two separate issues. How low can I drain the oil?

It sure looked like the transmission was the source, it was super foamy when I looked into it, but hard to see just through the fill cap. One test I could do I suppose is to not engage the PTO and run the tractor for a while, shut it off and see if I still get the bubbles. I will say when I drove it for a bit today it does seems to have a slight howl in the drivetrain somewhere. I dont feel/hear the same when I drive my dads.

Do you have a pic that shows the back end of the transmission where it bolts to the housing where the hyd pump is? I am curious where the holes are in between the transmission and hyd housings, to allow oil to pass through other.

Thanks,

Donnie
 
I bet its coming out of that hole, that sure looks like the area where it comes up.

The log splitter is not hooked up. I can hook up a bushhog, I did today, but it leaked down pretty quick.
 
Okay, show and tell time. I drained some oil, as JMOR suggested. Drained it so it was just above the hole going to the transmission.

https://youtu.be/8pAAcPi-BwI

It is coming from the transmission. I never ran the PTO pump. Here is a video of inside the transmission.

https://youtu.be/Wl7rW2VQ5Eg

Any ideas?

For the leakdown I will try what JMOR and Hobo suggested, first a relief valve hoping it is bad. And if thats not it I guess the next step is to drop the pump and inspect the exhaust control valve closer and post pics.

Thanks again for all the help, been an adventure on this one so far.

Donnie
 
Did some more investigating. I checked Dads tractor to see what it looked like. Looks the same to me, quite a few bubbles in it as well.

https://youtu.be/3TKaJkYI0cw
https://youtu.be/pZlXz4_a3Ok

Here is another video of my Uncles.

https://youtu.be/nOrJrCXJoZg

Is this just typical and I happened to catch it while troubleshooting my lift problem? Curious if anyone else has seen this. It wouldnt be the oil would it? Is the traveller full mineral 90wt from TSC.

For my lift issue next step I will try is the PRV, just waiting on it to come in.

Thanks,

Donnie
 

I don't think I ever ran one with the lift cover off, I would suspect quite a bit of curing if gears were spinning.

As far as the aeration in the hydraulic sump that's not normal is it the oil I dunno...

Could you back off a bit on the video... I take it the clutch is out and in neutral...
 
I didnt want to run it without the transmission top plate on. This is looking into the fill cap while it is running with my phone. Thats about all I can see or take video of that way. Yes that is neutral with the clutch out.

Thanks,

Donnie
 

I missed this one


https://youtu.be/8pAAcPi-BwI

That one is trowing us a curve ball a still pix makes it look like a bad leak I think you cheap arse oil is a issue as far as the aeration effect...

I run 80/90 are Ford 134D in my N's life is good...
 
Well crap. I thought that the TSC or Napa oil was the right choice from what I read!

Thanks for helping out Hobo, it is much appreciated.


Donnie
 
(quoted from post at 21:32:55 07/21/20) Well crap. I thought that the TSC or Napa oil was the right choice from what I read!

Thanks for helping out Hobo, it is much appreciated.


Donnie
ocket the camera & find the hydraulic leak.
 

Someone sure used more than their fair share of Red RTV... I would like to know what the deal is with the oil that's weird as ell...
 

Yes on the red RTV, not good is it.

If the PRV does not fix it. Next thing to check is exhaust valve? Or should I hook air up to the test port? 1/2-20 bolt I think I can drill a hole through the middle and tap a fitting for air.

Donnie
 
Update on the tractor.

I got the prv in the mail. Went to install it and the check valve pulled off the prv and stayed in the pump. Went to pull the tractor in the shop to drop the pump and as soon as I cranked it something has broke in the engine or transmission. Big knock when cranking. Great.

Pushed it into the shop by hand. Dropped the pump. I took some pics of the exhaust valve. It is pitted on one side. Will it be okay to turn it so the good side is facing the hole or will it spin? Also whats the purpose of the plunger/spring inside this valve? It looks like the valve just floats in the housing.



mvphoto59094.jpg


mvphoto59095.jpg
 
(quoted from post at 04:33:32 07/28/20)
Yes, I don't have a good feeling about this nor when he said part of the PRV stuck on the pump...

The check valve came off, I guess the spring was worn that holds it. It was just sitting in the pump once I removed it and got it on the bench.

The exhaust valve bushing does not have any noticeable grooves and feels smooth. I tried to take a picture to share, but did not get any to turn out. Understand about the tolerance, the valve does feel tight and I could not get any side play when trying to wiggle the valve. My concern was pitting. And I could not find the bushing or the exhaust valve for sale, is this correct that they do not make these parts anymore? Agree the valve pitting does not look good. However, they said this weak lift and leakdown issue came on quickly. Would suspect if it was the pitting it would have been a gradually worse issue over time. I am not ruling out a ruptured tube either, is there a good way to test it?


The knock issue was the gear on the starter broke, so getting that fixed. Then will test the hyd pump again.
 
(quoted from post at 10:13:40 07/28/20)
(quoted from post at 04:33:32 07/28/20)
Yes, I don't have a good feeling about this nor when he said part of the PRV stuck on the pump...

The check valve came off, I guess the spring was worn that holds it. It was just sitting in the pump once I removed it and got it on the bench.

The exhaust valve bushing does not have any noticeable grooves and feels smooth. I tried to take a picture to share, but did not get any to turn out. Understand about the tolerance, the valve does feel tight and I could not get any side play when trying to wiggle the valve. My concern was pitting. And I could not find the bushing or the exhaust valve for sale, is this correct that they do not make these parts anymore? Agree the valve pitting does not look good. However, they said this weak lift and leakdown issue came on quickly. Would suspect if it was the pitting it would have been a gradually worse issue over time. I am not ruling out a ruptured tube either, is there a good way to test it?


The knock issue was the gear on the starter broke, so getting that fixed. Then will test the hyd pump again.

The only source for the valve and bushing is used or NOS that is rarer than you know what. Live with what you have.

TOH
 
Sorry it has been a while, took a bit to fix the flywheel and repair the right axle before the hyd pump could be tested again. Last thing that was done was replaced the pressure relief valve. That was the fix.

Thank you Hobo, JMOR, TOH, and others for the help.

As far as the bubbles from the transmission, not sure what exactly causes that, but both my dads and uncles did it. Maybe the oil, we used the TSC traveller all mineral. I read some other posts that seemed to have a similar issue.

Thanks again everyone for the help, much appreciated.

Donnie
 

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