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Ford 8n Hydraulics

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flameeater

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Just wanted to get someone with more knowledge's input before I spend money or tear anything apart for rebuild. My 8n SHOULD if in proper working condition be able to lift an implement even at low RPM right? As of right now it lifts, but only at high RPM, and after it gets warm it really gets sluggish. I checked in the inspection port and I didn't really see any leaks, or whirlpooling. The fluid was jumping a bit right on top of the pump, but I think that is normal, if not please correct me. I took a video of what I saw, and uploaded it to youtube, if anyone cares to spare me about 25 sec, and let me know if you see anything I didn't I would appreciate it. I suspect a pump rebuild, or new pump is in my future. Thanks all!

 
Oh, and yes I did have the PTO engaged and lift controls were at the top. It was running a bit below half throttle at this time.

Also, I noticed there was no gasket on the inspection door. I am pretty sure I bought some to go there a while back when I was going to investigate this (and just didn't get around to it). It has never leaked a drop out of that door, so is the gasket necessary, or am I hallucinating about there being one there?
 
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flameeater said:
Just wanted to get someone with more knowledge's input before I spend money or tear anything apart for rebuild. My 8n SHOULD if in proper working condition be able to lift an implement even at low RPM right? As of right now it lifts, but only at high RPM, and after it gets warm it really gets sluggish. I checked in the inspection port and I didn't really see any leaks, or whirlpooling. The fluid was jumping a bit right on top of the pump, but I think that is normal, if not please correct me. I took a video of what I saw, and uploaded it to youtube, if anyone cares to spare me about 25 sec, and let me know if you see anything I didn't I would appreciate it. I suspect a pump rebuild, or new pump is in my future. Thanks all!

Click to expand...
Have you got enough fluid in there.
I find my 8N's do better with 90 wt in them.
 
Richard G. said:
Have you got enough fluid in there.
I find my 8N's do better with 90 wt in them.
Click to expand...
On the dipstick it is at the top of the full mark. I would assume the dipstick is correct, unless it has been swapped out for some reason before I got it.

Looking at the video again it comes up to the bottom of the inspection doors bolts. I would think you wouldn't want it much higher than that lest it would start dumping out when you remove the bolts.
 
 
flameeater said:
Would this gauge work? Just screw it into the port at the bottom of the pan, and see what it reads?

Click to expand...
Probably a bit of overkill. I think the max pressure is 1700psi, so a 2500 psi gauge would be fine. The treads on the test port if memeory serves me right a a bit different. Maybe different than the gauge but I really don't remember. found this: /8n then the corner test port on the hyd pump is a 1/2-20 bolt thread.
 
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flameeater said:
Would this gauge work? Just screw it into the port at the bottom of the pan, and see what it reads?

Click to expand...
NO!!!
The test port thread is 1/2-20 UNF. Screwing an NPT fitting into that port is a recipe for stripped threads and a split casting. You need an appropriate adapter.

Based on rhe symptoms your lift piston is likely leaking. All the gauge is going to tell you is pressure is low and you already know that. The trick is to figure out where its leaking off.

TOH
 
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TheOldHokie said:
NO!!!
The test port thread is 1/2-20 UNF. Screwing an NPT fitting into that port is a recipe for stripped threads and a split casting. You need an appropriate adapter.

Based on rhe symptoms your lift piston is likely leaking. All the gauge is going to tell you is pressure is low and you already know that. The trick is to figure out where its leaking off.

TOH
Click to expand...
Thanks for that. I am having a hard time sourcing this. I am looking for a male unf to female npt correct? Does it matter if it is flared on the unf side?

Rather than leaks I an actually worried more about the pump itself. The odd thing is, when I get it raise the lift with a blade on it, and I park the tractor with the blade up. It can take a really long time before it drops the blade. A day or two if I am remembering correctly. Wouldn't that rule out the piston? I am really new to hydraulics honestly.
 
mhb@ufe said:
Put an implement on the three point hitch, raise it up and shut the tractor off. Then look and see if you can find a leak.
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LOL I was responding to Hokie when you posted this. I will try this when the storms around here ease off a bit. Out of curiosity, if the piston is leaky, how long would one expect it to hold up a blade?
 
The drop rate would depend on how bad the leak is. In your video the cylinder looks dry so the problem is very likely in the pump. The fact that it stays up as long as you say I would suspect the relief valve.
 
flameeater said:
Thanks for that. I am having a hard time sourcing this. I am looking for a male unf to female npt correct? Does it matter if it is flared on the unf side?

Rather than leaks I an actually worried more about the pump itself. The odd thing is, when I get it raise the lift with a blade on it, and I park the tractor with the blade up. It can take a really long time before it drops the blade. A day or two if I am remembering correctly. Wouldn't that rule out the piston? I am really new to hydraulics honestly.
Click to expand...
Heres your fitting

www.discounthydraulichose.com

6405-05-04 | #5 SAE/ORB Male x 1/4" NPTF Female

Check out the deal on 6405-05-04 | #5 SAE/ORB Male x 1/4" NPTF Female at DiscountHydraulicHose.com
www.discounthydraulichose.com

As I said - a pressure test isn't goung to tell you anything you don't already know. At low RPM the pump is not producing enough flow to offset a leak somewhere in the system. Could be the pump or something else.The trick is to find the source. The piston is an easy one but you seem to have ruled that out. My advice would be keep RPMs up and dont worry about it.

TOH
 
Hi guys,
From post 12:
"It can take a really long time before it drops the blade. A day or two if I am remembering correctly."

If that is so, then I'm thinking---

The little check valve is sealing off the port to the two side chambers.

The exhaust valve is sealing.

The prv is not relieving.

The pressure circuit is not leaking from the bottom of the pump to the piston.

Suggest check the top clamp bolts on the side chambers, perhaps one or both have loosened up.
 
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