Valmet 646 hydraulic woes

leeroyjd · April 16, 2012, 03:20:02 PM

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 · April 16, 2012, 05:43:24 PM

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 · April 16, 2012, 05:56:36 PM

Quote from: leeroyjd on April 16, 2012, 03:20:02 PM
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 · April 16, 2012, 09:56:19 PM

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 · April 16, 2012, 10:09:29 PM

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 · April 17, 2012, 05:28:29 AM

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 · April 17, 2012, 08:40:05 AM

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 · April 17, 2012, 05:34:50 PM

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

snowstorm · April 17, 2012, 05:43:58 PM

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 · April 17, 2012, 08:29:47 PM

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 · April 17, 2012, 09:24:56 PM

seems like thats a sanden compressor and it is 12v

leeroyjd · April 18, 2012, 08:23:24 PM

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 · April 18, 2012, 08:47:53 PM

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

snowstorm · April 18, 2012, 08:53:47 PM

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 · April 19, 2012, 04:09:39 AM

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 · April 20, 2012, 07:02:49 AM

my book talks about the spring also as being the problem

kiko · April 22, 2012, 11:22:54 AM

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 · April 23, 2012, 06:27:23 AM

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 · April 23, 2012, 08:11:35 AM

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 · April 23, 2012, 07:55:26 PM

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 · April 23, 2012, 08:03:04 PM

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 · April 24, 2012, 04:27:03 AM

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

snowstorm · April 24, 2012, 06:44:05 AM

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

leeroyjd · April 24, 2012, 07:27:04 AM

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.