Control spool valves "O" ring and top seal replace confusion tightness

This topic contains 9 replies and was last updated by kenneth-lutz 8 years 3 months ago
June 10th, 2013 9:13pm
Well this is my first o ring replace on the Kontac valve stack without taking fully out and apart. I just want to stop the oil leaking out of control valves. I started to drop out the spool from underneath valves (bottom)and it is not sliding down and out. Is binding about an inch or so after dropping. I am wondering if I should take apart centering spring which is at the bottom of spool and then travel the spool up instead and maybe not have this problem ? This is an 1988 machine. It is an LB620 New Holland. I need some expertise in this repair and hoping some one will give some experience and guidance. Also I can not even get all the parts from MFG. "O" rings they have,,, I especially need the top valve pack seal (harder plastic surroundment.) to keep out the dirt. Any and all help or where to go will be appreciated.
June 11th, 2013 7:02am
I need to make sure that you understand that the small lip seals and O-rings you find in control valves are low pressure seals. They are there to prevent slight seepage from escaping and making a mess. If you have a quantity of oil, that means that the primary sealing surfaces are failing. Those surfaces are the lands of the spool to the drillings of the control valve, a very tight, metal to metal fit between the spool and the hole.

If you have excess oil, or any pressure at all on the lip seals or the o-rings, it is the fault of the valve assembly itself. It could be wear, it could be scored, but if there is a problem in the control valve, throwing o-rings at it will not cure the leak; only delay it.

The clearance is precise: maybe 5/10,000 of an inch, holding back 5,000 PSI. You need to figure out where the actual leak is, it could be that an o-ring has worn out because of dirt, but that would show in the area of the spool where the o-ring rides.

If something is stopping a spool from coming out, it very well could be a sliver of metal from a pump or motor or something else. You were wise not to force it.
June 12th, 2013 5:26am
Yes Thanks Jim, I do see some scoring on the outside facing the rear out toward the toothed bucket. I had put a stone rub on the surfaces before starting to drop the spool down and it had no relief. So now I am going to push up on the spool to take out. But first I have to take out the centering spring assembly. I started today but the hex bolt is not accessible for socket to torque it loose. It is deep inside a cupped retainer for the spring fixture. It is cupped so close nothing will grab it to loosen it! Yet. So now I am thinking (lots of wood burning) to push on and against spring retainer cup retainer with driven socket and handle to compress spring to access bolt hexes and go counter-clockwise after hopefully engaging it to loosen. What do you think? Thanks ken
June 13th, 2013 3:16am
I suspect that if the centring pin is forced down with a spring, all you are likely to require is a magnet and a pick to remove it. Wiggling the spool with the magnet there may also work. Use your magnet in the oil feed holes to see if you pick up filings. Check the filters and the magnetic screen in the tank.

Don't force anything, remember the close tolerances.

Was a pump or motor replaced that may have contaminated the system? If you find particulates, you may have to hot flush and filter the entire system. Look for dead spots where oil does not flow well, things can accumulate there and sporadically re-enter the system.

Hope you get it working.
June 13th, 2013 11:30am
No Jim never had any mishaps like that thank goodness.When I ran it everything worked like a charm. With the other email The scoring on the spool at top is horrendous and I am fearful it will damage dirt/dust wipe. So I am looking for an inexpensive way to coat smooth again. Any help will be appreciated.
June 14th, 2013 4:09pm
Well I did the removal of spool to the topside after centering assembly removal from below. That top spool area were the dirt/dust shield surrounds has a lot of gouges and non roundness for an effective future seal to say the least. It would chew up the new seal in short order. Also now I can see why it did not want to just drop down through valve casing. With all the deep valley made it has raised the metal surfaces and restricted with a larger diameter. First I am going to reduce the high surfaces, then hopefully add some filler to round smooth for dust shield. I figured I would send a pic or two of this problem.
June 23rd, 2013 2:32pm
Well here I did the resurfacing of the gouged spool valve using a solder technique. At first I was a little sloppy with the acid as it was like water I should of been a little more exacting for the application as will be shown in pics with a darker color to the non-soldered surface. But the covering I did after three applications with a torch and a solder iron I got most of the uneven out. This solder was specific to be used on steel bought on ebay .

June 30th, 2013 8:12pm
Well here I am back on the same non replaceable spool valve and now shearing the new o rings from mfg. So I decide to purchase smaller ones for replace so as not needing to hammer against spool valve. The original are way too tight. So I found about a .009 inch in diameter less to insert.(Buna -n). I am reinstalling soon the spool valve and 0 rings (two ways) from top down for bottom o ring seal ,then assembling centering spring at bottom and then pushing spool valve up for top o ring seal,from bottom up.I will definitely need extra jigging for this, as neither push can not go to far. In addition I had to modify the spool valve again to allow insert of new o ring . I took a quick pic of this.
July 1st, 2013 6:24am
It is really hard to tell from your photo's, but when you built up the seal surface on the spool, did you polish the surface while spinning in a lathe? The surface needs to be concentric and smooth for the o-rings to last. Obviously, is the surface is larger in diameter than it is supposed to be, the o-rings will be too tight.

Did you measure the spool with a vernier micrometer, capable of measuring to 10,000 of an inch? Using a tool like this requires practice and is a skill that must be developed.

Also, when you are handling the spool, you need to make sure that your skin oil does not remain on these surfaces. Your skin oil has acids in it that will etch or corrode this finally fitted and finished metal. You need to have rubber glove on, or keep your hands lubricated with hydraulic oil.
July 1st, 2013 11:43am
Thanks Jim for getting back, All the area where it is filled is finished by hand. Before I started to fill I took it down by some fine stones hopefully all the high spots left by the gouging. I would guess the silica and stones that had abraded it. I took a quick check with a micrometer 10,000ths inch readout to see if there were any high metal left on surface larger than 5/8ths of an diameter.(.6250") Of course this is not accurate as I am measuring from against from the other side of spool which could be worn possibly leaving an offset for its straightness. It was not easy to gauge the roundness with the micrometer by hand. So I took an extra stone rub just to make sure.(maybe .002") Then I finished with an Indian stone. Then cleaned with acetone then filled with the solder but not quite all of it after reveal of flat filling and Indian stoning. But area where it begins to seal interface on dust seal is fairly smooth and I feel should keep out most contaminants. I know the soft solder will not last as compared to the steel that was once there. I have been looking for a lathe for quit some time to no avail with my budget, and for that matter room. The outer seal or should I say the top seal is not the OEM as they do not have in stock any more and I think would of been little help anyway for flexability in this area. I will try and get a pic of the old one with the new one. Yes this is a backyard project and I probably would of not been allowed by the establishment of profesional peers to start and continue with it. Should we say a collectors refurbishment of the old. Any and all help will be highly appreciated all of the time.Later Ken

Reply to: Control spool valves "O" ring and top seal replace confusion tightness