Repairing a leaking joystick control valve

[willie59]

Well got 'er back together. Seemed to be okay. delay is gone but now machine has a left side weakness, goes forward and back fine, when i rotate full left or full right only the right track is turning. i swithched springs and plungers around and did not make a difference. Maybe ball resolver? maybe drive motor? I did notice that the ball resolver and the case for the plungers have updated, changed, part numbers. maybe time to dump the 1300 on new joystick complete, such a shame after a 500 sealkit!

Wow, that's a bummer!

Wish I could tell you what to do, just don't know with that one.

 

[Jason_W]

Hello,

I'm trying to change the seals on the pilot controls of a Cat 267B skidsteer. Having trouble finding the seals and o rings, cat parts doesn't break anything down past the actual plunger kit (289-8451). Wondering if I can use a generic U-seal & oring for this application, or is there a part number for the actual seals and orings from cat?

Thanks for any help.

Jason

 

[romer]

I am also looking for seals for a cat 236 skid steer. Where has anyone found them?

Thanks

Romer

 

[romer]

I am also looking for seals for a cat 236 skid steer. Where has anyone found them?

Thanks

Romer

 

[curb guy]

Thanks for this post Willie!! I noticed just the other day that the control on one of our 690e's is starting to leak pretty good.Good,useful info here!

 

[Randy88]

I've looked through the prior threads and knew willie59 would have one up for me to read, my hitachi ex100 has had problems twice now with the pilot control for the arm control, the arm goes out and locks there under a load, the last time it came out of it on its own, this time its not, its in the pilot control valve, we got it narrowed down to that, now my question is, do we need to rebuild it or is there something lodged or stuck in it that just needs to be cleaned out? If so what, someone told me to take it off and blow it out with air, is this a good idea or not? I noticed yesterday that there is a height difference of the plungers, the one that controls the arm out, which is the direction its stuck now, is a lot lower under the plate.

Now my second question is, why did it clear up and work fine the last time, which was about 7 years ago, so its had a lot of hours put on it since then?

 

[willie59]

I noticed yesterday that there is a height difference of the plungers, the one that controls the arm out, which is the direction its stuck now, is a lot lower under the plate.

If that, in fact, is the case, the plunger that controls arm out does not come up to the same level as the other three plungers, definitely sounds like you have a problem there. Just what's causing the problem, how it can come and go, hard to say. Could be a broken spring, could be the retainer C-clip is awry, could be a fragment lost in there that occasionally hits the right spot and causes the control spool to stick.

Sounds to me like it's time to take that PPC control valve apart. Very important, as you take it apart, mark orientation of all components, including how PPC valve is mounted in console. Do not mix up where parts came from as springs are different and plungers are different. Aside from paying close attention to disassembly, PPC control valves aren't that bad to service, it's a bigger PITA simply removing them from the console.

 

[250c]

Great post!

 

[Randy88]

My rebuild seal kit is supposed to be in tomorrow, so we'll see how things go, I didn't have time today to tear it apart to see whats inside it and how things look, but I'll find out tomorrow and post the results here so others know how it turned out, thanks willie59 for the input and taking the time to respond, also excellent thread on a detailed description of how to tear the valve apart, otherwise I'd end up like most, with a pile of parts and no idea where things go back in the right sequence.

 

[willie59]

I hope it all works out well for ya Randy88.

 

[Randy88]

It was a two hour drive to the shop, so I took the valve along to make sure I had all the parts I needed, they took it apart and found the one spool that controls the arm was stuck down, we dismantled the whole valve assembly and the only thing we could come up with was there had to be something like grit or debris that locked it down, once we got it apart we couldn't find a thing wrong, no broken springs, nothing, so we cleaned it all up and put a few new seals in it and put it back together, got it home put the valve back into the machine, willie is absolutely right, the worst part is getting it out of the machine and back in again. We've run it all afternoon and it works flawlessly.

Thanks for the informative thread willie and taking the time to help me out, your description was spot on for the disassembly and reassembly process, the pictures were a major benefit.

 

[willie59]

That is awesome news Randy88, good to hear you got it sorted out.

The tolerances of those spools in the bores are so close, it only takes a small fragment of something in there to muck them up. Once you disassemle the unit and clean it, likely the problem won't come back again. Be sure and check the filter in your pilot system.

 

[leeroyjd]

If there are issues in pilot joysticks.i.e. bypass worn spools,bad or missing seals what effect can this have at the main vave bank?
I have a Valmet 646 forwarder with Mannsmann Rexroth joysticks.Lots of vibration and noise right at sticks.Used to only happen on very hot days and even then it was intermittent now it is almost constant. Functions are ok although a little slow/weak.
All pressures are ok and pump is new as is filter(s) and oil.
Dealer does not show any rebuild parts except for a seal kit.Someone has suggested switching sticks as the left one does not seem to be as bad as the right one,which is used more.
Thanks,Leeroy

 

[willie59]

Welcome to the forum leeroyjd. :usa

Are you saying pilot pump was replaced? If so, did the original go to pieces inside? What was the condition of the pilot system filter when you changed it?

I suppose it's possible to switch the left and right joystick, never tried it myself. Keep in mind, most joystick PPC valves have certain configurations of springs inside, switching left and right might give a different feel in the wrists.

 

[leeroyjd]

Thanks for the welcome and reply!
There is no pilot pump- just a main pump on this machine.The main pump was fine internally.Shaft sheared off when trannsmission went.
As far as switching right to left I'm hoping this will confirm it is the joysticks that are the problem.
I'm guessing just a seal kit will not help.
If there is a lot of bypass within joysticks will this cause a noticeable change in oil temp?

 

[willie59]

Well leeroyjd, I must admit I really don't know anything about the workings of a Valmet 646, but if the joystick controls are actually pilot operated control valves, pilot systems typically don't work at full system pressure, they typically operate in a range of 300 to 500 PSI. If that's the case with this machine, there has to be some form of pressure regulating valve that not only maintains this pilot system pressure, but also prohibits pilot system from experiencing full system pressure. Have you actually tested the pilot system pressure to make sure it's within specified range?

As for seal kit, most any PPC valve that I've worked on doesn't have any seals internally, the seals are only external, to keep oil leaking out of valve at spools and such.

As for bypassing oil, any hyd component that lets considerable amount of oil under pressure bypass around it (typically from component wear), the result is oil going through a restricted passage, which does in fact heat up oil. However, if you're experiencing considerable heating of oil in reservoir, I would tend to think the problem isn't caused by faults in pilot system as it's a relatively low pressure system, would take quite a while to heat oil in reservoir, rather I would suspect something wrong in main working system hyd circuits would be causing the heat problem. Excessive heat at reservoir is an indicator of a problem somewhere.

 

[theironoracle]

leeroyjd, there is a spring and ball, or spring and tiny valve, under an allen socket plug (about #6 boss) usually on one end of your main valve banks that regulate pilot pressure, remove and check for debris and broken parts. i have never worked on a 646 my experience is with timbco/valmet, and cat forestry without pilot pumps....theironoricle

 

[leeroyjd]

That would be the pressure reducing valve you are talking about,right? I have checked that and actually replaced spring and spool.I think this may be similar to Timbco/Valmet hydraulic set ups.
Pilot pressure is reulated by pressure reducing valve on end section of main valve bank.Pilot pressure is 550,right where it should be.I understand what you are saying about bypass in joysticks would not be enough to heat up the whole reservoir,but could it cause spools not to open fully on main bank or something similar?
The seal kit made no difference and I only got half way through switching right to left before calling it a day.

 

[leeroyjd]

I noticed that one of the lines,pilot or tank(forgot) was dry when I took lines off.Does this indicate anything?The machine had been running right before I took lines off bottom of joystick.

 

[nixs]

PPC control valves aren't that bad to service, it's a bigger PITA simply removing them from the console.

I don´t usually remove them from the consoles. Had one customer calling me after he dismantled his PPC and put it back in the machine, swing right, left and stick in worked but not stick out. He had mixed the T line with port 4 witch is the stick out. Bummer!

About mounting the brass guides and the retainer plate, i don´t recall ever having problem pushing the retaining plate down.