Valmet 646 hydraulic woes

[leeroyjd]

Joysticks "chatter",make noise, and vibrate  like I'm doing too many functions at once.Also can feel a slamming feel when running certain functions.Function pressures are ok except slew(need new relief inserts)Not sure how to check "servo"pressure.Is this the same as pilot pressure?

[Gary_C]

I've had a Valmet 644 forwarder and a Valmet 546 harvester and can't help much. On the chattering thing, I've seen that happen when you are driving over rough ground and just holding the joysticks will make the controls seem to chatter. And even with hands off, the controls can chatter because of loseness in the joysticks.

And I've blown up a new gauge trying to check their servo pressures before as their hydraulic diagrams left a little to be desired.

Best bet would be to call the service dept at your local dealer. When I would get stumped I would call Roland Machinery in Escanaba, MI and talk to Tim Gafner who used to work in the plant where they built those machines.

[snowstorm]

Joysticks "chatter",make noise, and vibrate  like I'm doing too many functions at once.Also can feel a slamming feel when running certain functions.Function pressures are ok except slew(need new relief inserts)Not sure how to check "servo"pressure.Is this the same as pilot pressure?

what part of the world are you from? i have a 646. any hydra problems are almost always the orings on the shuttle valves. standby pressure should be 120psi its on the right side of the valve bank standing behind it. the small pump on the motor is for the breakes that should be 1600psi it will jump to 2000 every few seconds thats because on the alclumator. servor press should be the same as standby press. that is not ajustable. i have the parts book and tech manual such as it is they didnt spend a lot of money making the books. the valmet feild rep is in mi harvey dont recall his last name. i do have it somewhere

[leeroyjd]

alright thanks for the ideas.I'm from Rhode Island and have had good luck with Roland and the Oliver stores but have lousy cell service during the day so thought I'd try here. If there is a problem with accumulator will this effect hydraulics or only the brakes? Know about shuttles and have checked them all.Found out the hard way about the ball bearing in secondary shuttles!

[snowstorm]

accumulator is for breakes only. never had any trouble with the ball i leave it alone. its always the long one orings go missing causes all kinds of weird things to happen

[leeroyjd]

Hi Snowstorm,
     I had an o-ring kit for both shuttles and always wanted to check out the secondary ones.As you stated they were fine.
Two more questions:  Not building enough relief pressure in slew (swing) this seems to indicate I need new pressure inserts.Will this effect any other functions?
  Have you ever had to replace the A/C condensor? Oliver stores said 30 days and my a/c guys source is not doing much better.
   Thanks,Lee

[snowstorm]

the 646 uses an open center gear pump but it has load sensing pressure compinsated valves. thats why you can run 2 things at once. on the swing problem i say shuttle valve. i havent had good luck with putting new orings and backup washers on. also there is the wouble joint on the shuttle it wears. i went thru this when i first got mine except it was the bucket. it had very little power check psi its low turn in releif nothing didnt increase or not much. new shuttle an all is good.     your ac problem? the condensor is on the roof outside with 2 fans. evaporator is inside on the roof. tape off the outside air intake. just fills the unit with dust and lets the hornets in. the evaporator must be clean any dirt and it wont cool. break cleaner works good.  whats wrong with your condensor? is it a red dot? the hoses can leak thru the hose when they get old . for ac parts i use spaulding raditator in bangor. they know there stuff and stock a lot of red dot parts

[leeroyjd]

On the drive to work it hit me that I typed "condensor" but meant "compressor"! I'll try Spaulding,thanks!
  Lee

[snowstorm]

oncr you open the system you use a vaclum pump and dry it out also replace the dryer. i have bought quite a few parts from spualding good guys. he asked me if i had a pump i didnt so he said here take mine bring it back when your done

[bushmechanic]

Try the automotive bone yard,I have gotten a lot of compressors for A/C systems and retro fitted them for use on heavy equipment.The only difference is automotive system is 12 volt and heavy duty is 24 volt.All you have to do is install the clutch coil from the origional compressor.Snowstorm is right on replace the dryer when the refridgerant is evacuted,and make sure that there is enough oil (PAG) in the system because that is what keeps the compressor lubricated.

[snowstorm]

seems like thats a sanden compressor and it is 12v

[leeroyjd]

found a compressor but got another question: I have low pilot pressure. all functions work but I do have the aforementioned issue w/ joy sicks.What else will low pilot pressure/servo pressure effect? There was a spring on the end valve section that we were told to shorten up a few years ago but now I'm told this is why I have low pilot pressure.
  Thanks,Lee

[snowstorm]

not sure on the piolt press. my book says 120psi and that it is not ajustable

[snowstorm]

i wouldnt be surprised if all your hydra probs are the shuttle valves. like i said i dont even try new orings anymore. they are so hard once you get it on it wont fit in the hole. if you push to hard it cuts a peice off then it dosent work.when those orings go missing they end up somewhere they shouldnt

[leeroyjd]

Alright I'll go back over shuttle valves,most are new but I did o-ring a couple and they did'nt go in as nice as the new ones.Looks like they updated the shuttles to me.
  I also discovered I have low pilot pressure(should be 500 it is 250).Managed to get a call through to Valmet tech and he told me to replace spring on end section-so I'm waiting for that.So what problems would low pilot pressure cause on this 646 system?

[snowstorm]

my book talks about the spring also as being the problem

[kiko]

Does this machine use a pressure reducing valve to generate pilot pressure? Is that the spring you are speaking of?  Most systems have some sort of "servo " filter. Some are as small as the end of a pencil, as on the parker k 170  valves. If this filter is stopped up it will make every pilot controlled function slow.

[leeroyjd]

     Snowstorm-when you've replaced shuttle valves did you do all of them at once?I had only replaced ones where I could not adjust relief pressures.I am going to try that next on advice from tech.Tech also told me that I need to rebuild the shock load valve getting bypass there.Pilot pressure is where it should be 120,my book said something about 500 to joysticks.Reducing valve is in end section and I have new spring on order.Some parts for this machine are getting harder to come by.
    On top of these problems my pressures were all over the place.A friend came down to help troubleshoot and his gauge said 3500 where mine said 2750 on main pressure relief setting!
    Kiko- could the pilot filter be internal on the end section? There are some inline filters near the aux valve bank but I'm pretty sure they have no relation to pilot.  These books are especially vague to me.
  Lee

[snowstorm]

no i dont do all the shuttles at once. usually you can tell whitch one is bad. i agree on there books they arent much. what parts are hard to get? havent had any trouble at all. dose your bucket open slow in cold weather untill the iol warms up?

[leeroyjd]

Yes the grapple can be slow in the cold until warm up.What should that mean?What hyd oil do you use during summer months?
  Parts that are no longer listed include the spring on the pressure reducing valve and the pressure relief inserts on the shock load valve for the slew(swing)
  Lee

[snowstorm]

the bucket is really slow at -20 even at 30 till the oil warms up. aw68 for oil. they used rexroth valves . arent they owned by parker now?

[leeroyjd]

Not sure about the Parker thing.
  Have you ever changed any cartridge valves that are right underneath the joysticks?
Lee

[snowstorm]

no i havent changed any. do your joysticks move real easy?

[leeroyjd]

No just the noise I get right at the joysticks has me guessing.You know a mechanic named Flint from Maine? I've heard he is the one to find problems on these Valmets.

[snowstorm]

yes i know him.

[kiko]

I hope this works. If it does this is a break down of a k 170 valve. 01b is the tiny pilot filter.

 

[kiko]

Yes!! I finally figured out this picture thing, and all I had to do was follow the directions. It's on now!

[snowstorm]

Yes!! I finally figured out this picture thing, and all I had to do was follow the directions. It's on now!

thats a rexroth valve used in a 646??? dosnt look the same

[kiko]

I know nothing about a 646. I was only making the point that there should be some sort of pilot filter. With the parker K 170 valve the pilot filter is in the end section with the pressure reducing valve. This was a "for example" situation. All the pilot operated systems I have dealt with had pilot filter. Some systems have the pilot filter located in the accumulator charge valve that provides oil to the pressure reducing valve.

[snowstorm]

i have my 646 in the garage. so i did a little research. the pilot psi is 550. you do not check it at the valve behind the cab. there is a cover about 5' long just above the rite ft tire. there is a test port there also what looks like an in line filter.

[snowstorm]

might also want to check the coils. mine didnt shift the gear box replace the coil ($30) now it shifts as it should

[leeroyjd]

Thanks for all advice.
  I managed to break off allen head in blade primary shuttle and did'nt have a good enough drill bit to get it out! It looks like I missed checking this one somehow.
  Snowstorm,you may know this is the blade section which is the first section in the valve bank.If there is bypass at the primary/and/or secondary shuttles will this effect hydraulic flow anywhere after that?
  Thanks,Lee

[snowstorm]

i have been told that if one shuttle is bad moving the valve next to it will make it work. you need a good 3/8 drive 3/16 allen always hit it with a hammer that will help break it loose. the coils are on all the elc over hydra valves. you have diff locks gear box crane netural ect. if the coil was weak could it cause the controls to chatter? the crane netural coil. the 646 is not a simple fowarder not as complex as a new one but it sure aint no old timber jack or tree farmer

[leeroyjd]

   Got  coils on the way,although the float appears to be working fine.When you activate float switch you can feel it in joystick,just a quick pulse.Sound the same to yours?
   Both the grapple open and extend out functions have a delay.It is not the switch at the joysticks so it is either bad wire or a  faulty solenoid at valve bank,right? If so do you think this could cause these hydraulic issues?
   I'm going to set up gauge for pilot pressure while I'm running it to see if there is a drop or spike when it makes this noise/vibration.
New primary and secondary shuttles made no difference.At least that is ruled out.Most needed replacing anyhow.
  Leeroy

[snowstorm]

my bucket is only slow in cold weather. no delay when warm. what i was thinking if the coil is weak for the crane netural valve it may chatter. try to enguadge. i replaced the onefor the 2sp gearbox. sometimes it would try to shift. but it wouldnt hold it in. new coil all is good. what was your pilot psi? did you look at that filter?

[leeroyjd]

Been away from computer, all pressures are okay,problem still unresolved.I'm going to check the spool in unloader valve this am to see if it is stuck.Anyone had this happen?
   Thanks,Lee

[snowstorm]

everything checks out ok but it still dose it?

[leeroyjd]

     I bought two new gauges 4000 psi and 1000 psi and pressures are right where they should be . previously used 6000 psi gauge which I now realize was not accurate for the lower readings. 120 standby 550 pilot 2750 main relief and all the function settings are right on.
     If you hold your hand or press your foot against cab interior next to valve bank while loading you can feel slamming.Could it be the relief valves opening and closing because main spool is sticky or stuck? Raining so I don't think I'll get to it this am.