49 8N Hydraulics Won't Keep Rear Blade Up

[Bartman1959]

I've had this 49 8N for several months now, and just went through a really hard winter here in Idaho. Before the winter, the blade would stay exactly where I put it. After winter passed, there was water in the hydraulic fluid, so I changed the fluid. Now, it only takes a few minutes for my blade to go from the full UP position to the full DOWN position on it's own. The blade works great, other than it won't stay up. What is the repair for this?

 

[bamboozled]

Assuming you mean it falls down after you disengage the pto or shut off the engine, its probably seals in the lift cylinder, from my previous research that was usually the culprit. Open the inspection and see if you see fluid leaking out of the cylinder while the 3 point arms are falling. If that's not it, it could be leaking past the valve in the hydraulic pump.

I rebuilt the hydro pump on a 2N a couple years ago, but in that case the 3 point wouldn't lift at all. The culprit was the valve in the back of the pump had seized up in its bore over winter, was stuck open and was not allowing the pump to build any pressure.

The 2N and 8N use a similar pump, but a different valve type to control the lift cylinder.

 

[Bartman1959]

That's exactly what I mean. It just started raining here, so it will be a day or two before I can open the inspection cover.

 

[lennyzx11]

I've got one apart on my 47 2n right now if you need pix or anything.
I ordered the NAA lift cylinder piston with the leather backing ring a top rebuild kit and a pump kit along with a new control valve to rebuild it all at once.
Doubled the price of my "investment" in the tractor!

 

[Bartman1959]

lennyzx11, any pix would be great. At this point, I have no idea what I'm going to be looking at. I still have some research to do. Thanks

 

[N2DFire]

My father & I just did this to our 49 8N

Replaced Cylinder, Piston, Complete Seal Kit, new Pressure relief valve, and fresh oil.

It's actually pretty simple to do. I pretty much used these 2 videos for reference. I figured if they could do it we could too (my apologies if they are members here somewhere lol)

(It will only allow me to embed 1 video per post so I just linked them instead)

Part 1
FORD 8N HYDRAULIC LIFT ARM REMOVAL & REBUILD - YouTube

Part 2
FORD 8N HYDRAULIC LIFT ARM AND PRESSURE RELIEF VALVE INSTALLATION - YouTube

All the parts came from All States Ag Parts All States Ag Parts | Used, new and rebuilt tractor parts, combine and skid steer loader

They sell from their site as well as E-bay and sometimes the e-bay prices were cheaper. I called them on the phone, gave them all the part numbers & e-bay ad numbers and they put it all together as one shipment instead of me splitting orders from the web site & e-bay and paying shipping twice.

Extremely nice folks to deal with.

 

[Soundguy]

I'd put the naa piston in, good cnh oring, use a brake hone to clean up the cyl. Relief valve? Your call.

New cover gasket, inspection port gasket, and the 3 gaskets under the lift cyl.

No gasket goop!
Soak the leather backup washer in hot water prior to install.

With domed end of piston facing up on a table, install washer first, then oring.

Some leather washers are coming black faced both sides, son are tan, smooth on both sides, some tan, smooth on one side, roughish on the other, some surprise you and show up as a cupped synthetic ring.

The cupped syn, ring obviously instals with cup to oring.

The double black and double smooth tan, no difference.

The tan, smooth vs shiney.. I used to hear it made a difference, and only did it one way, but since then, I've done it both ways with no noticeable difference.

All it does is keeps the oring from being pushed into the ring groove edge shoulder, oring does the sealing.

 

[N2DFire]

I'd put the naa piston in, good cnh oring, use a brake hone to clean up the cyl. Relief valve? Your call.

New cover gasket, inspection port gasket, and the 3 gaskets under the lift cyl.

What he said. Soundguy is definitely the expert & he will get you fixed the most inexpensive way.

I was in a rush yesterday at work and I just put what we did, didn't have time to elaborate on the "Why".
For us - the biggest issues driving our parts selection was time. The tractor was taking up the only floor space in a one bay shop plus (with 1 F/T & 2 P/T jobs) I have limited days I can work on it so we were looking to do this start to finish in one weekend and get it out of the way. If you have time to work in phases (tear down & clean, order parts, rebuild) then you can almost certainly get by with less "stuff" and less money.


Piston - Yup definitely use the newer style NAA piston with the rubber / leather o-ring. No point putting back the metal ring style that failed when you have better choices.

Relief valve - cost $18 and almost 70 years old (and apparently a newer design - what we took out did NOT look like what went back). Was more of a piece of mind thing for us. Also caused the need for removing the PTO shaft & dropping the pump / bottom plate because we just couldn't get the right combination of tools and hand size to get to the valve otherwise. There are numerous accounts of others doing this on the internet, but it didn't happen for us. In hindsight - it might be possible after just removing the PTO shaft. Hopefully I'll never have to find out.

Cylinder - 100% agree it's not required. But for us it was just easier to go ahead and do it. My logic / concerns were that we'd bust the thing open and find scratches too deep to hone out & then have to order more parts (and pay more shipping) and the extra wait time. Plus we don't have a hone. Even a cheap Harbor Freight one is $26, the cylinder is $46 (on e-bay, almost 60 on the web site - same vendor). The $20 difference was worth not having to wonder / wait.

Gasket kit - $14 and has gaskets for everything on the rear of the tractor including the piston o-rings. O-rings alone are $7. Again more parts than you "need" but if you get in there and found other issues or needed to remove the PTO or bottom plate, you already have the gaskets to put them back.

One word of advice - use a lift or hoist (or an assistant) or something to remove the top assembly. Don't try to man handle it. In order to get the lift control rod in the correct place and not damage it, you'll end up in some pretty awkward positions & that thing is fairly heavy.

Your needs will vary but regardless of what parts you decide to replace, the overall project is very simple & straightforward.
Best of luck.

 

[Bartman1959]

After reading your comments, and watching the videos posted on here, it looks like I'm going to have to put up with the dropping three point for a while. I don't have a lift/hoist or assistant right now, so being a "one man show," I'll wait until I have a proper setup before tearing into the hydraulics. I definitely don't want to get in over my head.
Thanks guys, I really appreciate your help.

 

[Soundguy]

if you can lift about 65#, you don't need a lift or hoist.

you take the seat off

you pop the pins out of the 3pt knuckles and toplink yoke. 99% of the time.. that part right there.. getting the pins out.. is your biggest deal. use lots of penetrant oil.

remove the perimeter bolts on the top cover, don't remove the inner bolts.. yet.. they hols the cyl to the top cover.

the cover almost lifts straight up, but easier to lift front of cover first and start coming up with it, then move forward a hair, then up.

you will have a long arm hanging down. it freely fits in and slips out of a control valve on the pump. ( during reassembly, you remove the inspection cover so that as you lower the top cover in place, the little control arm has to go into the slot on the control valve. ) the inspection cover gasket can be rtv'd.. but all other gaskets must be clean n dry.

there will be a top cover gasket, a 2-3" oval gasket under the cyl, and 2 dime sized gaskets under the cyl.

the old gaskets must be cleaned off. i use a razor blade, spray carb cleaner and then a scotchbrite.

remove cyl.

use an air hose with a rubber tip to pressurize the oil hole on the underside of the cyl a bit, hold your other hand with a rag in it cupped to recieve the piston that will be shoooting out. don't air it like you are firing a howitzer shell.. just a few psi will pop it out.

if it's a 3 ring steel piston.. set aside and get the new naa oring and backup washer piston.

take a brake hone to clean up the inside of the cyl.. even if it looks immaculate, which they seldom do.. at least put a crosshatch on it. if it is scratched.. just run it around till at least sharp edges are cut down. the CNH oring is beefy.. you can actually hone that cyl past it's book tolerance and still get a good oring seal.. thus, if honing the scratches and you can get them out with a little extra.. go for it.

clean the bore out good.

install backup washer then oring. lube them well to help get them on.. a spoon helps witht he leather washer after soaking it.. and don't roll the oring.

a light chamfer with a rat tail at the mouth of the cyl assists in insertion of the piston without cutting the oring. lube it before insertion.. grease.. oil.. etc...

domed end in.. oring should be the first entering, backup washer last.

dogbone rides loose in the cupped end of the cyl

new dry gaskets.


easy peasy.


if you do the relief valve.. just reach in.. it unscrews like a spark plug.. etc. you will be reaching around the pto shaft.. but with top off and side cover open.. it's no problem. you can actually change it from the side cover alone with stubby wrenches, or long wrenches torched to put a lazy bend in them. BTDT.. all 3 ways are no sweat...