# hydralics on a 790



## joshc (Aug 16, 2010)

I added a loader to my 790 a few weeks ago. I've used it a few times lifting some heavy items and that kind of thing. Now, if the forks or bucket are a couple feet off the ground with no additional load, I can start to pull back on the lever to raise it and it will actually lower until I pull back harder to get pressure build up. Any ideas what is wrong? It's pretty dangerous when unloading something because I have to really give it all she has to raise it.


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## Hoodoo Valley (Nov 14, 2006)

Sounds like you are over loading it. Will it hold it if you put it to neutral position? Does it do it with a lighter load?


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## joshc (Aug 16, 2010)

Yes it will hold in neutral. It will do it with only the buck or my forks on it. Today I was hauling some small branches from a Bradford Pear Tree and it was terrible! Nothing heavy at all and i had to watch what i was doing so not to dump the load!


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## Hoodoo Valley (Nov 14, 2006)

Well, it sounds like a bad valve, then. is it just the loader or the bucket too?


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## Hoodoo Valley (Nov 14, 2006)

Sure you have it hooked up correctly in terms of the hydro lines? Sounds also like the hoses might be incorrectly hooked or in the wrong spots.


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## joshc (Aug 16, 2010)

It's both actions, curl and lift. 

It's not the hoses because as I said, if i gently pull back on the handle to lift, it will let down or bleed of per say and once I pull back hard on it, then it will finally lift. Same exact thing as the curl.


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## joshc (Aug 16, 2010)

Here is a video I stuck on youtube showing exactly what it is doing. 

Any ideas????

[ame="http://www.youtube.com/watch?v=Ia-5eUZOu8g"]790 Hydralics[/ame]


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## joshc (Aug 16, 2010)

I left it parked with a little bit of a load this evening and it is bleed off pretty quick. I left it about half way up and it's dropped about 4 or 5 inches in about 3 hours.


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## Hoodoo Valley (Nov 14, 2006)

Welcome to the world of advantage series John Deere loaders. My 990 does that in a matter of an hour.


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## joshc (Aug 16, 2010)

This thread has had 47 views, I wish we had some more ideas.


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## Hoodoo Valley (Nov 14, 2006)

SCV is defective? You said the hoses are hooked to the right spots and proper........ Contact the dealer if you just bought it. Should be warranted!


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## joshc (Aug 16, 2010)

Well I just bought the loader, but I bought the tractor from an individual, its a 2006.


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## Hoodoo Valley (Nov 14, 2006)

Have you consulted the dealer at all on this issue? I believe the loader is fine.


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## joshc (Aug 16, 2010)

I know the loader is fine, it's in the valve I'm thinking. I haven't talked to the dealer yet, but will tomorrow!


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## wolf21 (May 8, 2011)

it sounds verymuch like it is the valve...i worked on hydraulic systems rebuilding cylinders and valves at the factory i worked at[till it went south] and with the way hydralic valves are ported inside, it should not:

a) be possible to go in opposite direction
b) drift in that short of a time period...

it sounds like the port spool edges are worn/bleeding by... so when you move partway into 'up' it is bleeding by to tank and letting it drift, then when you move it farther the channels on the spool move far enuff to seal the blowby, and it begins to lift normally. in the video it seems as though it is a smooth up action at the start of the movement ...so either the spool/ports are worn, or if it is brand new...the spool might not be centering properly, and letting it cross the wrong ports first, allowing the drift before the up... my ford loader has sat 6 months without drifting...and it is 27yrs old...your new JD shouldnt either


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