641 3 point bobbing and drifting down #3

SStra

Member
OK after pulling cover and re-doing o-rings and pulling check
valve, and safety valve washer - still have bobbing and drifting
down. Priced safety valve and control valve - both over $100 now
from CHN.

So finally did what I should have from the beginning and removed
the PTO cover. Main piston not showing any leaks. But got a stream
of oil coming out from front of cylinder body, assuming it is from
the control valve also seeing some leakage at back of control valve
that drips off of the control rod.

Will post some pictures along with this - not sure if or how to post
movie clip but I have one I could.... Picture will not show it but the
stream of oil hiccups (assuming it is when the lift bobs). And in the
one clip I have it looks like a little oil may be coming out of the
back of the unload valve when I see the hiccup. But that is nothing
compared to large stream of oil in front and dripping in the back.
Of course I can not see the front cover very well just see the stream
of oil.

OK now for the questions.

Looks like I need to pull the control valve and bushing. What do I
need to do that. (What size bolt to screw it and pull it - and how do
I remove the bushing - (socket and press?)

Next question - appears that there are really three different control
valves. Do I remove mine and find the color and then order one
from CHN - - or can I just order a matching color of bushing and
valve from CHN ahead of time.

Next question - while I am there - do I pull the unload valve - - if
so what bolt size do I need to pull that and once I get the plug out
what do I need to push the unload valve out.

Sorry a little wordy - but trying to paint the picture so you can help
me.
a170545.jpg

a170546.jpg
 
I did some more reading of manual - control valve spool looks like it comes right out once the baffle and retainer plate are removed. So no bolt or tool need there.

Control valve bushing looks like I can either put a bolt through the middle of it and pull it out or use a press and correct size socket to push it out. Manual does not say which way to remove it.. towards open or close end. May not matter looks like it is all same size. But to reinstall they are pushing from open end. Any suggestions?

Since I have oil leaking form both front and rear of valve seems my only course it to renew. Looks like I need to know color code on my control valve and order both control valve bushing and valve spool. MY CONCERN is manual STATES "[b:654c4848f0]the correct size control valve spool can be determined on by selective fit after the bushing has been pressed into the cylinder casting.[/b:654c4848f0]" HOW DO I MAKE THAT WORK..... CNH said they do not have a control valve but can order one for me.. So no way am I going to be able to selective fit after bushing has been pressed in. Please tell me what I do here?

______

Unload Valve - hoping that it will only need a new o-ring - but to get there need to pull the plug. Manual talks about a impact driver which I do not have. Assuming I need to screw a bolt or all-thread in it and pop it out. Can you tell me what size threads I will need to screw into the plug. Size and course or fine would help.

Thank for and any and all advice - just do not want to make worse or screw up and have to replace complete high dollar lift cylinder.
 
(quoted from post at 10:37:14 10/02/14) OK after pulling cover and re-doing o-rings and pulling check
valve, and safety valve washer - still have bobbing and drifting
down. Priced safety valve and control valve - both over $100 now
from CHN.

So finally did what I should have from the beginning and removed
the PTO cover. Main piston not showing any leaks. But got a stream
of oil coming out from front of cylinder body, assuming it is from
the control valve also seeing some leakage at back of control valve
that drips off of the control rod.

Will post some pictures along with this - not sure if or how to post
movie clip but I have one I could.... Picture will not show it but the
stream of oil hiccups (assuming it is when the lift bobs). And in the
one clip I have it looks like a little oil may be coming out of the
back of the unload valve when I see the hiccup. But that is nothing
compared to large stream of oil in front and dripping in the back.
Of course I can not see the front cover very well just see the stream
of oil.

OK now for the questions.

Looks like I need to pull the control valve and bushing. What do I
need to do that. (What size bolt to screw it and pull it - and how do
I remove the bushing - (socket and press?)

Next question - appears that there are really three different control
valves. Do I remove mine and find the color and then order one
from CHN - - or can I just order a matching color of bushing and
valve from CHN ahead of time.

Next question - while I am there - do I pull the unload valve - - if
so what bolt size do I need to pull that and once I get the plug out
what do I need to push the unload valve out.

Sorry a little wordy - but trying to paint the picture so you can help
me.
a170545.jpg

a170546.jpg
he burp of extra oil at front, whenever a correction occurs, is normal, as this is the dumping from the unloader valve as it returns to unload position at end of correction/lift.
Finger is tool to remove control valve spool. Press to remove/install control valve bushing. I guess you are doing this without benefit of FO-20, since you can read it all there, including a full discussion on spool/bushing sizing/matching. Good $ spent to buy one. 1/2x20 bolt & stacks of washers to remove unloader plug, then thin rod to push valve out.

P.S. Later post indicates that you have manual....good move!
 
I agree with JMOR, the flow up front is normal.

The oil around the unloader valve / control valve is not. This is a picture of my 660.



It was a badly worn control valve that was causing hiccups.

But is sure is worth trying the unloader valve first. Make sure you get the correct o-ring. I would get one from CNH. Here is a couple of pics on how I got the plug out.





A piece of plate with a hole would work just as well. Be aware, the bolt is fine thread.
 
JMOR and Kurt thanks for the reply - I will insure I have a fine tread 1/2 bolt before I start.

Just to make sure I am understanding - I have a continual flow of oil that is larger than twice the size of the lead in a pencil all the time. You informed me the burp out of the unload was normal, just want to be sure the continual flow is normal.

If so, yes I may just try to change the o-ring in unload valve. In looking at it I believe I am getting more oil at the bottom of the control rod than I see coming from the back of the unload opening.

But I have more time than money and pulling with a hoist. Sound like to fix these you have to pay your dues and pull them at least three times.

Just hate touching that control valve because of Price and the fact that it is metal on metal. Sounds like in the old days they had multiple valve and bushings and test fit until they found a good match. Now days sound like you give CNH a couple hundred, bring home a valve and bushing and hope they match-up ok after you get it in.

Anyone changed the control valve out lately, and if so how did it work out for you.
 
"just want to be sure the continual flow is normal. " No, not normal. But........because the control valve and the controlling section of the unloader valve (not the activating part with ring) both rely on metal to metal sealing, I would not be surprised to see some very small drip type leakage occurring, especially on old worn equipment. A double pencil lead size stream would seem to be a bit much. I'm afraid that actually isolating the leak may prove to be somewhere in the range of very difficult to impossible, as, if you examine the construction, you will see pressure paths in annular rings around the unloader plug, around the control valve bushing, and unloader bushing. Granted, spool to bushing wear/erosion would be the most likely as compared to those other non-moving interfaces, but anything is possible. I only mention these other possibilities so that you will be aware that there is always some possibility that problem will not be solved even with all new bushings & spool. Fairly complex bunch of paths here. Somethings, we may just be destined to live with.


 
You said " Sounds like to fix these you have to pay your dues and pull them at least three times". I think you have it right. The good news is that it gets easier every time. Took me 3 tries to get my 660 working perfectly. You go in, fix what you think it wrong and then do it again and again until you are done. Wish there was a better way. The good news is that it is worth it.

Also, I fully understand you comment "I have more time than money" Since I retired, I can afford to spend a day on these things.

Best of luck

JMOR - Nice pictogram of the cylinder. I think I'll steal it. Thanks
 
(quoted from post at 11:33:25 10/03/14) You said " Sounds like to fix these you have to pay your dues and pull them at least three times". I think you have it right. The good news is that it gets easier every time. Took me 3 tries to get my 660 working perfectly. You go in, fix what you think it wrong and then do it again and again until you are done. Wish there was a better way. The good news is that it is worth it.

Also, I fully understand you comment "I have more time than money" Since I retired, I can afford to spend a day on these things.

Best of luck

JMOR - Nice pictogram of the cylinder. I think I'll steal it. Thanks
urt, I do those not only for my benefit, but for others, so use it as you like! You ended up replacing the entire ram/valve assembly with a good used unit didn't you?
 
Your memory is good Jesse. I picked up a used cylinder on Fleabay an gave it a try and got lucky.

I checked into rebuilding the control valve on my original cylinder. CNH has a .001 oversize valve. But that was a gamble at best. I toyed with making one. They are very simple, but my machining skill don't go along with .0001" tolerances. My cylinder is sitting out in my garage, maybe someday I'll try.

BTW, I sole you pictorgram already.
 
Follow-up

Still bobbing and major oil leak at the front of lift cylinder after pulling check and back pressure valve and replacing that o-ring.

So put a new safety valve in it - - that helped the bobbing and drop down after shut off a BIT but still getting oil at front.

So pulled it again and pulled the Unload valve and replaced the o-ring. Also replaced the spring and 7/16 ball on the check valve. And adjusted linkage.

Back together and now I do not have the stream of oil at the front of the lift cylinder. Can not see any bobbing and drift down after shut off now takes 30 minutes or so. Draft control working as it should.

Still getting a very slow drip of oil under the control valve rod. But with the price of the control valve and bushing I believe that I will call it a completed project for now.
 
(quoted from post at 15:41:20 10/10/14) Great to hear you got it working. Taking that top cover off three times usually does the trick.
he more times you remove/replace, the lower your acceptance threshold becomes. :)
 
Sure does JMOR! I wish there was a better way to diagnose these problems. If you can't pinpoint the problem, your only choice is to fix what you think might be causing it. If you are right, you celebrate. If you are wrong, you take the cover off and try again.

YUK!!!!!!
 

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