JD F935 mower with hydraulic problem question

[JeepsAreBuilt]

Hello,

I have a JD F935 mower with the diesel motor and a 72" deck. I've had it for a few years, and the hydraulic reservoir would needed to be topped off periodically. When it gets low the steering gets harder to turn. The other day I started mowing and the steering quit completely and the deck wouldn't raise. I was still able to move it back to the shop. I checked the reservoir, it was empty, I could see the bottom. So I topped it off, and started it back up. I looked in the reservoir and it looked like no fluid was circulating. So I tried turning the steering wheel back and forth a few times to bleed it somehow. But, still the fluid didnt look like it was circulating, or the level did not go down.

I thought maybe the filter has plugged up ?

Any help or ideas how to fix this problem ?

Thanks

 

[Roadworthy]

The filter (if it has one) could indeed be clogged. I think the bigger problem is finding where the fluid is going. You have a very definite leak somewhere. It could be a hose, a fitting, a seal, or a gasket but you should address the leak. It sounds as though it's getting worse and they don't fix themselves. Once filled I don't top off reservoirs. Levels stay up until I change fluid. In any case I'd call the leak a symptom, not the problem.

 

[JeepsAreBuilt]

Yes, the leak should be fixed..

I looked at it some more today, it will start and move forward and reverse. Does this mean the filter is not plugged up ?

 

[zzvyb6]

Check the hoses on the lift arms. F935s have the valve for the 2 function (as in snowblower chute rotation), but yours may not be fully plumbed for it. Check the valve body for leaks. My mower uses a sight-glass in the middle of a return hose for checking fluid level. If this is broken or leaking, there can be a fluid stream whenever you touch the deck lift function or the steering cylinder. All my hoses have disintegrated and needed to be replaced. AND, there is a hose underneath that is not protected properly and can get snagged on things you run over or graze. Park in on concrete after starting it. It will appear when you cycle the leaking connection.

 

[Amvcane]

If the leak is slow over time and doesn’t even show itself, I would lean towards an axle seal. The seal is pressed into the diff case and when it leaks the axle tube fills up with fluid. The axle nut will be wet along with the brake drum.

 

[JeepsAreBuilt]

You guys sure know your JD mowers..

I checked out the sight tube, and it was full, almost all the way to the reservoir. So, I'm not sure if it was even low at all. I also read on other threads that its normal for that reservoir to be empty and, the level not to be low. However when I touched the sight tube, the tube just sheared in half, so I need to replace it now.



Looks like that axle seal is leaking on the right side.. another thing I need to fix. The left wheel is clean.



The hydraulic filter I have on there has about 180 hours on it now..



So I plan on changing that filter, and hose. Check the hoses to see if any are loose and need tightening, also see if the charge pump is tight. I dont think there are any catastrophe leaks thats making the hydraulic lift and p/s not to work. Are there pressure relief vavles that could be causing the problem ? Also the lift control valve has not been working right.. the float detent wont stay on, I just have to keep and hold the leveler down and it floats. I was going to try to fix this valve or replace it with a ebay one. I dont know if this problem would be related ?

 

[Amvcane]

Jeeps,
Here is a bunch of videos showing how to change the axle seal. This is on a 318 which is basically the same tractor as your F935 just driving in reverse.
o61
- YouTube
If you change the suction hose under the filter make sure to save the spring inside for the new hose. The spring stops the hose from collapsing under vacuum.
Your float detent is unrelated and could be worn from using it every time you drop the deck or the detent springs and balls could be stuck. Not sure which valve you have.
Here are the hydraulic bleeding procedures used to remove air from the system. They are in a specific order just like you bleed the brakes in a car.
Hope this helps.

 

[JeepsAreBuilt]

I'm still having trouble getting my f935 operating,

I finally got around to fixing the broken fluid level sight tube today. I also changed the hydraulic filter. It still has no hydraulic power. Strange thing is that after changing the filter, I caught about a quart of fluid and the fluid level in the sight tube barely went down. I only added maybe 1/2 a pint to get it right in the middle. I think it never was low on fluid.

Ive been searching the internet for ideas to solve the problem. I checked the pump charge relief valve, I tried to let air out of it while the mower was running, no fluid pushed out. I shut it down and pulled the valve out, and a little bit of fluid dribbled out. It seems to me that the pump needs to be primed somehow. Any ideas for me ?

I took a couple of pics..



This is the pump.. I took both relief valves out, one at top and then one on the side. There are 2 big nuts with buttons, what are those ? They are popped up, and I push them down, and they dont do anything.



This is the steering valve.. looks like a lot of work to pull out to check to see if theres something plugging up inside of it.

 

[chris young]

Any update on this hydraulic issue?

My friend is having a very similar issue with his older F935 front mower. He drained and replaced he hydraulic fluid but nothing works regarding the hydraulics. The mower was working 100% prior to replacing the hydraulic fluid. Is there a way to bleed the hydraulics system or could he have forgot to turn something back on? Thanks!

 

[JeepsAreBuilt]

Any update on this hydraulic issue?

My friend is having a very similar issue with his older F935 front mower. He drained and replaced he hydraulic fluid but nothing works regarding the hydraulics. The mower was working 100% prior to replacing the hydraulic fluid. Is there a way to bleed the hydraulics system or could he have forgot to turn something back on? Thanks!

Yep.. I've gone though everything on my hydraulic system.. I found broken springs in my steering column.. waiting for parts to come in to fix it. Hopefully it'll fix my issue.

For your friend, Did he change the filter at the same time ? If so, the service manual says to fill the filter 1/3 to 1/2 full of fluid before installing it so it will prime the charge pump. So, if he did not do that, then I would first make sure the hydraulic fluid is topped off(by looking at the sight glass under the floor board. Then take the filter back off and fill it, and reinstall. I would jack up the front tires, and bleed the hydraulics by pushing forward then reverse repeatedly. Then operate the steering and loader.