# Loader Won't Lift



## TurboSteve

Hi all,

My father-in-law has a JD 790 with a 419 loader that i've been using to move some dirt around. The loader just up and quit lifting, though the bucket will curl and the three-point works fine. There's fluid going to the barrel side of the rams, but not to the shaft sides. My father-in-law said this happened once before and they replaced the selective control module under warranty. I was wondering if this is the problem again, and if so, is the valve rebuildable or fixable without taking the tractor in?

Thanks,
Steve


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## Live Oak

Sounds like a blown o-ring/packing in the lift circuit of the SCV. The SCV's are rebuildable. If the tractor is no longer under warranty, I would suggest that you call the dealer and ask if they can repair the SCV if you remove it and bring it in to them.


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## TurboSteve

Alright, thank you. Is this problem due to poor product quality or abusive use? The tractor only has about 400hrs on it and its four or five years old.

Thanks,
Steve


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## Live Oak

Pardon my manors Steve. Welcome to Tractor Forum! Glad you found us! Steve, it is difficult to say whether it is abusive use since I am not able to observe your operating. It is very unusual for the SCV to go out a second time in so few hours. Can you give me a brief description of what you were doing at the time you noticed the failure? 

The SCV AIN'T cheap at $790! I looked up the SCV and linkage and there is no repair kit listed. 

You can buy specific parts for the SCV from the image below. If it is not an o-ring, most likely is a check valve stuck or possibly a spool damaged or sticking. You will have to remove the SCV and disassemble it to inspect for any damage or problems. Could be that something has gotten stuck in the hydraulic oil passages and jamming up the works.


<img src="http://www.tractorforum.com/attachment.php?s=&postid=92363">


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## Live Oak

John Deere lists a seal kit for this SCV under part # AM117916 that lists for $19.50. I would take the other SCV apart and inspect it before you look at buying another SCV. Could be is it just a blow o-ring or other seal. 

Worst case, the SCV is listed under part # LVA802784 and price lists for $790. If you have to go this route, you might ask the dealer parts guy if they can get rebuilt SCV's. Probably not but might be a possibility. Below is the SCV and linkages to give you an idea of what you are in for, taking the SCV apart. Good luck with it and hope the seal kit is all you need.


<img src="http://www.tractorforum.com/attachment.php?s=&postid=92365">


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## Archdean

Welcome also , most systems have a relief valve that is set to open when your lift capacity is exceeded, perhaps the pressure is set too high and or the valve failed to open causing an "O" ring to fail... and it may be just stuck in the open position due to dirt etc.
Recommend that you drain and change hyd fluid and filter first, then exercise the system at least 10 times thru all cycles to their maximum travel!!

PS. You didn't state if the fluid level was checked for being correct! I assume that it is and that you have bleed the system!!

Good luck


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## Live Oak

Last question I had was, have all the services and inspections been kept up on this tractor? (ie: oil and filter changes, inspections, etc.) Only reason I ask is IF the hyd. oil potentially has some contaimination in it such as water; this could get circulated through the system and also freeze causing problems and or damage. Anyhow, hope I was able to give you some ideas and things to consider. Keep us posted on your progress with this problem. Lots of folks here that are very knowledgable and ready to help out! :thumbsup:


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## TurboSteve

Once it stopped working, we immediately checked the fluid and found it to be quite low. We filled it but that didn't do anything. Then we drained the fluid entirely and i checked the filter underneath where the lines cross over, but that was clean. I think we're all on the right track though with the seal/o-ring/check ball problem. You can pull or push on the lever and it strains the engine, but doesn't do much more than that.

I'm actually quite easy on the tractor compared to its owner, who works it quite hard and has used it to pull/dig numerous stumps (and other immobile objects) out of the ground. My friend was just scooping up dirt and dropping it in another location; nothing out of the ordinary, but maybe the repetitive motion finally wore something out.

My father-in-law just called and said he is taking the tractor to a nearby hydraulic place that said they could fix it, though i believe all of the replacement parts are only available through JD. If they try to soak him, i'll try to convince him to let us at least pull the SCV apart and see if we can find anything that looks damaged or jammed. If we can't fix it, then i don't think we will be any worse off than we are now.


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## Archdean

You most likely identified your own problem!! If your hyd fluid level was indeed quite low then filled but DID NOT BLEED THE SYSTEM you undoubtedly have air trapped in the cylinders and it wont lift period! your other cylinders will function normally!!

I would bleed it FIRST!


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## TurboSteve

How might that be accomplished?


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## Archdean

I'm not a JD Technician but the first thing that is normally done is to cycle full up and full down when the tractor and fluid is warm if it wont move the arms crack the RETURN fitting at each cylinder just slightly you should see bubbly (fluid/and trapped air) seeping and providing the system is full normal lift will soon follow!!

If it is a "broken O ring" then it must be replaced because the pressure side is bypassing directly to the return side giving no positive displacement to the lift cylinders!!

hope this helps you and others may be of more help!!

Dean


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## TurboSteve

I believe we more or less did that. We were tinkering with it this morning and with the tractor warm, we opened both sets of lines on the cylinders. The lines at the shaft end had plenty of fluid while the barrel end lines had nothing, not even a dribble.


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## Archdean

Interesting ! Will the bucket lift the front of the tractor? Ensure it is not in detent (float mode)?


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## TurboSteve

Someone else told me they though it might be in float mode, but if that's the case, i would think it has to be jammed in that mode via the SCV. It won't lift the front of the tractor. You can curl the bucket so it does and then hit the lift lever and it will expand the lifting cylinders, but it won't squeeze them closed.


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## TurboSteve

Well i didn't find out exactly what part failed, but it was six dollars and a whole lot more in labor. Oddly enough they messed up the bucket tilt now. If you push the lever all the way over, the bucket will just drop and empty instead of curl up. You have to just nudge the lever to get it to work. At least it lifts now though and i was avble to move my dirt.

Steve


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## Live Oak

That is progress but it sounds like the dealer guys may have gotten the hose connections reversed on the bucket tilt circuit.


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## TurboSteve

I'll have to double check them. They evidently didn't notice the diagram on the tractor fender and the corresponding colored markers on each line, as they marked the lines with a permanent marker.


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## Live Oak

Sure hope it is a case of CRS. :thumbsup:


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## fenceman

my 790 wont lift the front bucket either it has fluid and if you push the three point lever all the way back it lifts the bucket i think the o ring is the problem thanks for the info , fenceman.


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## fenceman

my 790 also has front wheel drive problems rebilt frontend 2007 model 560 hours only had 790 tractor before this one it had fornt wheel drive problems too it had 2 front ends rebuilt at john deere not good tractors you wood think john deere wood fix it free,


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## trucker101

Archdean said:


> You most likely identified your own problem!! If your hyd fluid level was indeed quite low then filled but DID NOT BLEED THE SYSTEM you undoubtedly have air trapped in the cylinders and it wont lift period! your other cylinders will function normally!!
> 
> I would bleed it FIRST!



I had the same problems as the other poster, my up/down isn't moving properly on my loader that is on my Tea20 tractor. How do you bleed the system? I want to do this as soon as the weather warms up more.


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