580C Loader Control Valve repair

[DirtyHoe]

I'm rebuilding the loader control valve on my 1980 580C. I don't think the insides have seen daylight in 40 years. The spool seals were leaking and most of my power beyond o-ring was gone. I've read the service manual and searched online for any information on what is acceptable wear on the main relief valve(pilot plunger and seat along with the poppet and seat). There are ridges and burrs that you can feel with a fingernail. Do they start leaking at this point? Some of these parts are no longer available to purchase. The service manual says to replace, but don't mention what the tolerance for wear is before replacement.

On the engineering side of things, why don't they seal on a chamfer like a load check valve and a secondary relief valve? These parts look brand new because they have more surface area to seal on. It does not make sense to me why the relief valve shuts off on a sharp edge instead of a chamfer. I could re-machine these parts to remove the wear grooves, but the would change the depth of engagement and diameter of the taper. I'm guessing this very small change would make it relieve at a different pressure. My concern would be the springs would not have enough adjustment to function at the correct relief pressure. Basically, I fear I would not be able to recalibrate the valve if things go wrong. Then I would be screwed trying to find good used replacement parts.

I can't believe the amount of innards in a hydraulic valve. AMAZING
Don't worry, I took lots of pictures...


Thanks for any help with this,

Steve

 

[DirtyHoe]

Someone has to know more about this than me. Is it wore out or OK? Do I replace the pilot plunger & seat since the parts are available or just put it back together and run it as is?

Thanks!
Steve

 

[mikebramel]

If there is a solid ring all the way around it should not be leaking

 

[melben]

That system has been used many years without problems, don't try to improve a proven design, the ring of wear on that seat is not hurtful if there is no groove worn in it, that is what we call a compound relief valve, the large plunger is held on its seat by the spring behind it and there is a tiny drilling in the screened poppet to allow system pressure to get on the back side of the plunger that causes system pressure to come into the spring area between the plunger and the main adjusting smaller needle and seat. as long as the needle is seated system pressure builds and the system pressure adds to the spring tension to hold the plunger tightly seated , when the system pressure builds to the point that the needle unseats the flow through the needle exceeds the flow of the tiny drilling in the large poppet and system flow pushes the poppet open, refacing the inner seat would not hurt system pressure, that is controlled by the outer point and spring and seat in the cartridge. I would be careful to make sire the drilling in the screened plunger does not have debris in it as that can cause system pressure not to get on the back side of the plunger and flow will push it open, I have re seated those needles to remove the ring of wear but I would also look at it's seat with a strong magnifying glass to make sure that there is not a groove worn in it, yes oil leakage will cut a groove in steel, The outer point and seat are available , they are at various dealers throughout the USA but can be pulled for you. If you are interested in checking other parts availability from a parts man that cares about what you need call Dan at 570 297 2144 He is an old timer and know his stuff, you can go on the CE parts site and look up the part numbers and that will help him even if they have been subbed he can chase them. You will not be sorry you use Dan, he know whats going on with the older stuff. Do not worry now about relief settings as the amount of work u are doing will require resetting at least the main relief and all others should be checked. More on that later!

 

[DirtyHoe]

Mel,
Thank you for the detailed explanation! That helps a lot. When you're not familiar with identifying the worn-out stuff like me it's hard to know what to replace vs what to put back together as is. It's too much labor to get it all apart and neglect to change something because of my ignorance.

Thanks for the education,
Steve

 

[DirtyHoe]

Below are some before and after pictures of a variety of parts. I sandblasted them, then they went to the plater. It's hard-anodized(black color) on the aluminum parts. The steel parts received zinc yellow-chromate and the rest are electroless nickel. The zinc yellow-chromate is what you would find on nuts and bolts these days. It provides excellent corrosion resistance. The nickel is better yet and offer some surface hardness. These parts should be better than original now. Painting small parts is a hassle and doesn't hold up. Plus you don't want to paint on the innards of the hydraulic parts.
The sandblasting goes pretty fast for me. I have a large cabinet with a siphon gun. But the siphon is slow for heavy paint and heavy rust. So I plummed in my Clemco pressure pot hose into the cabinet. Wow-what a difference. The pressure pot seems to go about 10 times faster than a siphon gun.
This is only half of what I had plated in the picture. I had about 80 pieces in total. Some pieces were much bigger like pivot assembly to my JLG 45HA lift. The total cost was about $200. Well worth it to me.

Steve

 

[DirtyHoe]

After rebuilding the valve, one of the two secondary relief valves is giving me trouble. It won't build up much pressure over 1,500PSI and starts leaking off before that. I've double-checked all the o-rings and backup rings. They are in great shape. I'm pretty confident it's the groove worn into the plunger by the seat(red in the photo). Since these parts are obsolete I don't want to mess it up. Does the seat press out from the narrow end of the main valve? My plan is to re-machine the two mating surfaces(plunger and seat) and then add more shims as needed for the correct PSI.

Steve

 

[DirtyHoe]

Has anyone had one of these apart? It appears to be pressed into a blind hole. It looks like I need a super small ID bearing puller. The bore is only about .25". Also, I can't damage it on the way out.

Thanks,
Steve

 

[Tinkerer]

I know this is an old thread.
Did you ever get the valve repaired to proper working condition ?
Smtnjim has a new thread and is needing all the help we can give him.