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View Full Version : Update: Success! Hydraulics out on JD770 tractor



pony4me
Aug. 21, 2011, 09:10 AM
We have an old, but (previously) dependable John Deere 770 tractor that's been able to handle our 23 acre farm just fine. Until the other day when the power steering and hydraulics ceased to function. Has anyone had that happen to them, what was the cause and is the fix expensive? Thanks!

Update: We got the bolts off, and the filter screen out. Hubby was expecting to see a small screen like a piece of window screen, but it was really very long, with tiny holes. He cleaned the screen per instructions in the owners manual, put it all back together and it works fine! We have steering! We have up and down implements! Now we have mowing to do.

Thanks to all who offered suggestions!

Tom King
Aug. 21, 2011, 10:15 AM
Fluid level okay? Last time hydraulic filter was changed? Won't even work after running for a minute or so? Visible leaks?

More than one possible answer for the information given.

pony4me
Aug. 21, 2011, 02:10 PM
Fluid level was ok. Just to be safe, hubby changed the hydraulic filter and replaced fluid. What he couldn't do was remove the screen that's near where the fluid drain plug is. There are three bolts that are in really tight. No visible leaks. When running, if you run the tractor for a while and then try to move the lever that controls implement height, it makes a hard-to-describe groaning noise. We are going to try to find someone with some more muscle power to loosen the three bolts, drain the fluid into a clean container, remove the screen, clean it, and then replace screen and fluid. Tractor has 625 hours on it. Bought new in 1990, replacing out 1953 John Deer 40.

Hpilot
Aug. 22, 2011, 04:30 PM
The loader might have a leaky seal in the ram. Mine made a groaning noise when this happened. That doesn't explain the power steering though.

MistyBlue
Aug. 22, 2011, 04:44 PM
Yup, groaning usually mean leaky seal IME. (not that I'm an expert by any means, LOL)

If it stops working or has a hard time working after being run for a bit...it's losing pressure somewhere most likely. Check hoses and seals.

And one other thing to check...I had the same issue with my NH 33...turned out to be a teeny tiny leak. Not enough to lose lots of hydraulic fluid, that stayed steady. But enough for condensation to get in and dilute the fluid.

What I did was drain some fluid from the bottom drain pan...let it sit for 12 hours and it seperated. Water on top.

Although if you drained it all and replaced it and it still had the issue...I'd still go with losing pressure somewhere. Because the hydraulics would be fine for a while before the problem popped up again.

mronthebit
Aug. 22, 2011, 09:29 PM
Either a leaky seal or a malfunctioning pump. Either way, if you can't solve it yourseld you may find the most expedient fix with someone at your local hydraulic shop vs. your local equipment dealer.

Belg
Aug. 23, 2011, 10:40 AM
If you haven't asked, you might also ask here :)

http://www.ytmag.com/jd/wwwboard1.html

It's been pretty useful on a couple Ford/N.H. issues too....