NAA stopped lifting weight

[seanpaintsflames]

I was mowing the field last weekend with a 6ft flail mower. When I started, everything was fine, but about an hour into it I realized that the 3-pt lift wasn't lifting anymore. If I rev the tractor up or wait a few minutes it will lift a little bit-maybe a couple inches off the ground. If I take the weight of the mower off the back, the lift arms seem to work fine- up, down, quick response- This flail mower is stupid heavy, though.

I rebuilt the hydraulics and flushed all the fluids over the winter when I bought the tractor, and it has worked famously since then. This was a pretty sudden thing. The tractor does sit outside all the time, and the UTF is a bit milky. I've let it sit, and I've taken the hex cap off the side to maybe relieve pressure or something... I dunno; I really don't know what's going on.

HELP! My grass won't stop GROWWWWWING!!!!

THanks!

 

[seanpaintsflames]

A little more diagnosis- With only a quick hitch connect on the lift arms, it will lift when the draft control lever is up. If draft control is down, it will not lift the weight, but it will hold it in place if already up. I checked the fluid while the lift was up, and it is right on full. The fluid is a little milky, but still golden.

 

[Soundguy]

hex cap on side?

this got a vane pump or piston pump?

what did you rebuild.. specifically?

have you pressure tested it? both hot and cold?

 

[seanpaintsflames]

How does one go about pressure testing the system? I don't have gauges or specialty tools.

It's got a piston pump.

About 6 months ago the lift hydraulics got all new gaskets and o-rings, a new piston with the leather and rubber seals, all the brackets were straightened, a new cam follower pin, and everything was adjusted as per the "alternate" method. The whole fluid tank got cleaned out flushed and new fluid. Like I said, the lift worked great until this.

The hex cap on the right side- the pressure valve or whatnot. Honestly, I don't have a complete grasp on how the whole hydraulic system works- When I took the top off for the rebuild, the pressure valve just seemed to sit there through the hole in the side case- it's not hooked to anything. Does the whole case pressurize, or what?

I don't know if the flail mower bounced hard on the lift arms when I let it down and bent something inside, or what. I'll just crack the top off in a minute here (now that my daughter is off to ballet for an hour) and see if anything is obviously awry.

 

[Soundguy]

sounds like you are talking about the back pressure valve that sets under an acorn cap nut on the side of the case. prior to removing the lift cover you MUST remove the nut and back off the back pressure valve to prevent damaging it. if you didn't do this step.. i'd look for valve/ring damage.

to pressure test you chain the 3pt upper arms to the axles. then you unscrew the plug in the 3x5 option cover on the top cover.. then you screw in a 3000 psi gauge, then you start tractor.. get to mid throttle, then exercise lift and watch gauge.

 

[Cbrown9064]

sounds like you are talking about the back pressure valve that sets under an acorn cap nut on the side of the case. prior to removing the lift cover you MUST remove the nut and back off the back pressure valve to prevent damaging it. if you didn't do this step.. i'd look for valve/ring damage.

I am about to remove the top cover on the 861 next weekend. Is this for the hundred series Also or just the NAA?

 

[DaveOmak]

That same situation/description happened to my NAA.... turns out it was the High Pressure Relief Valve that started leaking....

Dave

 

[seanpaintsflames]

So, there may be an oring or some seal between the valve and the hyd tank that is bad?

 

[seanpaintsflames]

Alright, here is what I'm looking at. I took the acorn nut off the side of the body, there is just a spring in there. I took the spring out, turn the tractor on, and a little bit of hyd fluid squirted out when I moved the quadrant lever around. I took the lift top cover off, and I don't see any sort of oring around the valve. I assume it is threaded into the tractor body, then the pickup tube is pushed into the side of the valve? It doesn't just push through the body, but it will turn. From what I can figure, the way that the whole system gets the fluid from the tank to the piston is that one hole in the bottom/side of the top cover that just rests against the pressure valve? If that seal is bad or not tight enough, then it's like poking a hole in straw, right? The fluid looks like it would be low to me, but the stick says it's good. What do ya'll see?
Thanks so much for helping me through this!

 

[Soundguy]

I am about to remove the top cover on the 861 next weekend. Is this for the hundred series Also or just the NAA?

only the naa has the acorn nut..

might want to invest in a service manual for your 00 series.