JD 950 Power Steering/Hydaulics Problem

[DJCohenour]

Good afternoon gentlemen,

New member and first post. I am impressed with the amount of knowledge in the hydraulics forum. I have posted this question in another forum with no luck. So, here goes:

I recently had to do some transmission work on my 88 model JD950 with FEL and backhoe attachment. I won't bore you to death with all of the details but, I had to split the machine, had the rockshaft housing removed, and had the diverter valve removed. I have the diverter valve and hydraulic line setup off of a 1050. How that happened I do not know.

Anyway, before reassembly, the hydraulic sump and suction screen were cleaned, a new filter was installed, and a nice $60 worth of JD low viscosity hydraulic oil was added. After reassembly, the 3PH and FEL work as smooth as silk with lots of speed and power.

The problem: I now have no power steering. It worked great before the other work was started. Now, I have no power assist initially. I turn the wheel until I hit resistance, hold the wheel there, and I will get a little power assist in about 10 seconds. This assist is only about 25% of normal. The entire time the wheel is being turned, there is a little engine RPM draw down, not bad though, and I can here the pressure relieve valve doing a little howling.

What I know: as stated above, the sump was cleaned, a new filter was installed, and new JD hydraulic oil was used. I thought at first I picked up a piece of dirt in the power steering lines and it was pushed into the PS control valve so I removed the lines and back flushed the control valve with compressed air. Started the tractor and no change. I then unhooked the hydraulic lines from the diverter valve and tried back flushing it compressed air with some success. I then reassembled the lines, started the engine, and no change.

Do any of you gentlemen have any experience with this diverter valve or have any suggestions? I want to pull the pressure relief valve out of it and continue flushing/washing the unit out, but I am afraid of messing it up completely. There is also a large "nut" on the back of the unit that will unscrew. I have not taken it out for fear of damage.

I had a few hours to work on the machine Sunday afternoon. I took all of the hoses off of the power steering control valve and cleaned it out. I put everything back together and no change. I then unhooked the pressure line going to the power steering valve and cranked over the engine a few times (didn't start it). There was barely a trickle of fluid coming out of that line.

I then determined which lines coming off of the diverter valve are supposed to have pressure using some very small flow diamgrahms in the service manual and deductive reasoning. Then I unhooked the other line that is supposed to have pressure coming off of the diverter valve, cranked the engine over a few times, and lots of fluid comes out.

The problem, I think, has to be in this diverter valve. It also contains a pressure relief valve according to the service manual. There is also a large "nut" on the side of this thing that will unscrew, but I am afraid of messing with on account of screwing it up.

I am now looking for a breakdown diamgrahm of this diverter valve so that I can take it off and apart for a cleaning. It is shown, greyed out, in the diamgrahms on JDparts.com but there are no part numbers or anything listed for it. It is acting to me like the pressure relief valve is stuck closed and not letting any fluid go to the power steering.

I will get this problem whipped. It will not beat me.

Ahhh, the joys of tractor ownership.

I really am at a loss as to what else to do. Any suggestions?

 

[kennyd]

Welcome to TBN

I think what you are calling a "diverter" valve is actually a "priority" valve. It dedicates a certain amount of fluid flow to the PS so it will always function. I have never had one apart so I can really help you...but it sounds like you are onto the problem.

 

[DJCohenour]

Kenny,

Thank you for the welcome.

I think that your are right about priority valve. I am simply using the terms in the service manual. The only information that the service manual has on this component are the pressure relief valve settings and how to adjust it. I do not know if this pressure relief valve is just for the power steering or for the whole machine, but I think that I am going to pull the priority valve off of the machine and carefully open it up. I can almost guarentee myself that there is a piece of dirt lodged in the pressure relief valve or clogging a little orifice.

Thank you for taking the time and effort to read my novel of a post and to formulate a response. Boards like this are truely invaluable.

DJ

 

[DJCohenour]

Kenny,

I was just looking on the Surplus Center website under the priority valves. The one that is on my machine looks a lot like this one: https://www.surpluscenter.com/item.asp?UID=2009041317150728&item=9-4017&catname=hydraulic

The only physical difference (I know nothing about the specs) that I can see is that mine does not have the 12 volt solenoid on top, but I can see the pressure relief valve sticking out of the top of it and the large "nut" on the back is there as well.

Thanks again,

DJ

 

[kennyd]

Kenny,

Thank you for the welcome.

I think that your are right about priority valve. I am simply using the terms in the service manual. The only information that the service manual has on this component are the pressure relief valve settings and how to adjust it. I do not know if this pressure relief valve is just for the power steering or for the whole machine, but I think that I am going to pull the priority valve off of the machine and carefully open it up. I can almost guarentee myself that there is a piece of dirt lodged in the pressure relief valve or clogging a little orifice.

Thank you for taking the time and effort to read my novel of a post and to formulate a response. Boards like this are truely invaluable.

DJ

My pleasure DJ, there are lots of people here who are eager to help...

The relief should just be for the steering, or it may be an adjustment that determines how much flow goes to the "prioritized" circuit and not a PRV (pressure relief valve) at all.

The system PRV should be located on the tranny somewhere I think-I am good with the newer stuff and only so-so on the older machines.

At this point, I say go for it! Take it apart, it does not work now so you have nothing to loose IMHO.

 

[kennyd]

Kenny,

I was just looking on the Surplus Center website under the priority valves. The one that is on my machine looks a lot like this one: https://www.surpluscenter.com/item.asp?UID=2009041317150728&item=9-4017&catname=hydraulic

The only physical difference (I know nothing about the specs) that I can see is that mine does not have the 12 volt solenoid on top, but I can see the pressure relief valve sticking out of the top of it and the large "nut" on the back is there as well.

Thanks again,

DJ

As far as specs go...all I can say is that the newer machines with dedicated pumps for the steering get about 3 GPM or for machines your size...

 

[DJCohenour]

UPDATE:

Bad news first. When I got home, I went to the tractor and wrote the name and model number of this "priority valve" that we have been discussing. After some web searching, I found the company, Modular Controls Corp., has been out of business for almost 20 years with no cross references for the part.

The good news: After some more web searching, I found an Ebay listing for the valve in question. The seller calls it a Power Steering Flow Divider. This seller even has a parts breakdown and list in his listing. Needless to say, I saved the graphic and the list into a text document.

More bad news: I checked the part number for the whole valve on jdparts.com. Thier price is $795! The actual valves in the assembly are no longer available, but the O-rings and such are still available.

eBay Motors: JOHN DEERE POWER STEERING FLOW DIVIDER AR93303 850/950 (item 140282012038 end time May-13-09 10:43:06 PDT)

This thing is not that complicated according to the diagram. Tomorrow evening, after work, I am going to pull this thing off and see if I can get it cleaned out. I am thinking that I will be better off in the long run if I go ahead and get the o-rings and put them in during reassembly.

Thanks for all of the help and advice so far. I will take pics of the progress.

 

[kennyd]

Great detective work DJ! I believe it's something you can fix...Replacing the O-rings will be money well spent for sure.

 

[DJCohenour]

UPDATE:

I got it fixed!! I cannot believe how simple it was. The hardest part was the space restrictions due to the seat and left fender.

A little closer:

And the actual culprit:

I think that there was more dirt and grime than tractor at this point in the day.

Anyway, I have the diagram of this valve so I decided to pull the 'big nut' (assembly 6) out of the back of it and just see what I find.

When this stem came out, it was painfully obvious what the problem was.

All I did was a little wiping off of the stem, installed a new o-ring at the point where the stem seats against the housing, screwed it back in, and had a good time getting some seat time.

I ordered all new o-rings for the assembly but the o-rings looked to be in such good condition, I just put them away until I have problems with it again. "It it ain't broke, don't fix it."

I really appreciate the help I have had along the away and hope that someone may find this helpful at some point in the future. This board is really great!

 

[Conservation]

Great work! I have a 1050, and I have not been that impressed with the hydraulic system. Doesn't seem like it has enough volume or pressure for what I usually want to do. Probably keeps me out of trouble though. I have noticed that if my rocker shaft lever is all the way up, or close, that what I think is the pressure releave valve howls. You can hear a bit of a tug down on the engine too. Not sure what that is about. I have worked my 1050 pretty well, and the only thing thus far has been a new clutch. So it has been a good tractor for me. Although I am having some concerns about the clutch again, but I will post a question about that for another thread.
Again, great job saving yourself a lot of money!