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Re: Ford 8N Hydraulic Raises on it's own and sticks up

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Bruce (VA)

08-04-2014 09:47:12

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When the lift arms raised all the way up, reach in the inspection port & push the control rod to the rear. (that's the rod that runs from the top cover to the pump:

If the lift arms drop, you found the problem: a dirty pump.

I agree that just changing the fluid won't get you much.

For info on changing the hydraulic fluid, check out tips 3 & 4 at the link below.

There are two ways to clean the pump; the “quick clean” that gets a lot of the sludge out of it, & the right way that gets all of it, including the hard packed crud in the pump base.

For the quick clean, after you get the old fluid drained out (overnight is best) remove both inspection plates & start pulling the sludge in the pump base out by hand. Then, get a couple of gallons of kerosene or diesel fuel & pour it into the pump base. Catch it in a bucket & reuse it. (Some folks use a hand garden sprayer.) Flush the pump base out 5 or 6 times. Do not start the engine to run the kerosene through the pump; kerosene and diesel fuel do not have sufficient lubrication properties for a 60 year old hydraulic pump designed to be immersed in 90w gear oil. Some folks say it’s ok to start the engine, engage the pump for a minute or two, then turn the engine off. Your call on that one.

This 'quick-clean' is not as effective as dropping the pump & doing a full job. But if the choice is between doing nothing & the quick clean, spray it out. It worked for me for 3 years on my 1951 N. If you have the time, drop the pump; that is the right way to do it. I’ve done it both ways & don’t plan on doing the quick clean again. That’s because dropping the pump is not a big deal. If you have hard packed crud in the pump base, you are wasting your time w/ the "quick clean".

With all of the fluid drained out, block the front wheels & get the rear wheels up at least a foot. (you'll see why soon enough) Remove the 4 bolts holding the PTO shaft in & pull it to the rear & out of the tractor. Loosen all of the bolts. Remove all but 2 corner bolts. Then, carefully remove them. If you are lucky, the pump will drop free (and dump a pint or so of hydraulic fluid down your sleeves). If not, wrestle it free. The pump has 'ears' that fit into the housing; wiggle it a bit & it will drop free. If you have the rear tires a foot or more off of the ground, you will have enough arm room to hold the pump & lower it at the same time. Put it on your work bench & remove the safety valve (p/n 638) and the control arm lever (p/n 643) which will allow you to remove the intake & exhaust valves (p/n’s 640 & 698) Drop all of it in a bucket of diesel (or mineral spirits) or your parts washer & let it soak overnight. Once it has a good soaking, get it on the bench & start blowing it out w/ compressed air. Run cleaning fluid into the hydraulic discharge near the test port & make sure you get a good flow out the small hole in the side of the pump were the control valve fits. I don't see much need to pull it down any further just to clean it. But, I always replace the safety valve (p/n 638, about $25) Reinstalling the pump is harder than pulling it out because you have a gasket to worry about. (no sealer on the gasket) And, you will probably need a helper to guide the control rod into the pump rocker shaft unless you’ve done this 6 or 7 times before!

While you have the PTO shaft out, it would be a good time to replace the seal on it. It's got two spring clamps around it. Take your needle nose pliers & remove the one in the front. Then, hang the shaft & bearing housing in your vice & tap the butt end of the shaft; the bearing cap will come off (and the shaft will land on your foot). Then, remove the other spring clip from the other side of the bearing. At this point, remember that you never bought a seal driver & go get a BF socket & drive the seal out. If you have the new style seal, the white side goes out. (open side to the oil) Put some grease on it.

Contrary to conventional wisdom, not a lot of water gets in the oil from the shifter boot. Of course, if it's bad, replace it, but you get water from the draft control spring & the dipstick. But, most water is just a byproduct of the heating/cooling cycle of the oil.

You’ll need a pump gasket, safety valve, inspection plate gasket(s), PTO seal, PTO gasket, gasket sealer & 5 gallons of fluid to do all of the above.

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08-04-2014 10:28:47

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 Re: Ford 8N Hydraulic Raises on it's own and sticks up in reply to Bruce (VA), 08-04-2014 09:47:12  
Thanks for the quick response. I'm still not quite clear on the control rod, I found the rod connected to the control above, when I raised and lowered it and felt at the bottom it seemed to be a plunger going into and out of hole, is this what needs to be pushed to the rear? I tried this but it didn't seem to move to the rear, only vertically.

A second question, in your tips you seem to imply there is no difference between the Ambra fluid and the TSC GL1 fluid. I was under the impression that the Ambra fluid is the better option for year round use, but it is $80/5 gallon bucket at the nearest dealer, compared to roughly $50 for the TSC brand. I live in Michigan and plan to be plowing snow in potentially sub-zero temps so I'd be willing to spend the extra money if necessary.

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08-04-2014 11:10:11

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 Re: Ford 8N Hydraulic Raises on it's own and sticks up in reply to WarnerT, 08-04-2014 10:28:47  
that rod should move a rocker back and forth.. if it ai'nt moving.. your valving is stuck... could be gritty oil, especially if it looks dirty.

I think bruce was telling you you can use ambrag or gl1.. not that they were the same oil.

ambrag is the utf fluid meeting m2c134d specs.

gl 1-3 90w would have been close to what was originally shipped int he rear end.

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08-04-2014 12:30:43

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 Re: Ford 8N Hydraulic Raises on it's own and sticks up in reply to soundguy, 08-04-2014 11:10:11  
So if the valve(s) are stuck should I clean it like Bruce said or do I need to replace those valves as well?

I meant that he implied they are functionally the same. I understand they are physically different, is there a consensus on if the GL1 works fine in cold weather?

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Bruce (VA)

08-04-2014 16:11:00

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 Re: Ford 8N Hydraulic Raises on it's own and sticks up in reply to WarnerT, 08-04-2014 12:30:43  
" do I need to replace those valves as well?"

Probably not.

" GL1 works fine in cold weather? "

It does in VA! But 30* is cold around here.

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08-05-2014 05:31:24

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 Re: Ford 8N Hydraulic Raises on it's own and sticks up in reply to Bruce (VA), 08-04-2014 16:11:00  
Update: I got down in there again last night and tried with all I could to get the exhaust or inlet valve to move by hand. No luck. The only thing I can figure is that the inlet valve is stuck open and the exhaust valve is stuck closed. Explaining why the lift raises as soon as you let go of the clutch with the PTO on, even if the control is in the down position, does this seem correct?

Secondly, I hooked up the back blade for weight and looked in with the PTO running. There's about a 1/4" stream of fluid running down from what I think is the ram cylinder. This explains why the arms fall down on their own.

So my thinking is that I have to fix that leak and I have to unstick or replace the two valves, and clean out everything, at a minimum. I think I have to concede to dropping the whole pump and cleaning it thoroughly and pulling the cylinder out also to repair that.

I'm assuming I should find out EVERYTHING that's wrong before I start taking stuff apart? I haven't drained any fluid to this point, so how much oil do I need in there to operate the pump and still be able to find additional leaks? As of now I'm still unable to see what's going on very well due to the fluid.

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Bruce (VA)

08-05-2014 05:40:48

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 Re: Ford 8N Hydraulic Raises on it's own and sticks up in reply to WarnerT, 08-05-2014 05:31:24  
" I'm assuming I should find out EVERYTHING that's wrong before I start taking stuff apart?"

Your diagnostics are very good. You've done about all that can be done at this point: you need a top cover rebuild & a pump cleaning.

Check out the link below for a step-by-step on the top cover rebuild.

Plenty of us around here have done both, so just ask for help if something isn't clear.

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08-05-2014 07:00:35

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 Re: Ford 8N Hydraulic Raises on it's own and sticks up in reply to Bruce (VA), 08-05-2014 05:40:48  
Thank you, will you re-post the link?

I'm not sure I want to tackle this quite yet but I'll take a look at the steps. Anyone have any idea how much parts might run me for this mess? If I do it I'm going to do it right and spend the money to replace whatever I can to not have to do it again in the near future.

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