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Hydraulic Problem - John Deere 2750

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KevinsJD
Join Date: Feb 2016
Posts: 5 Virginia
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2016-02-21          194577


Hi Folks,
I have owned a 1985 John Deere 2750 with 4WD, cab and loader for about 2 years now. After operating the tractor (mostly bush hogging) for 1–2 hours, particularly in hot weather, the hydraulics stop working properly. The 3-point hitch and loader bucket lift slowly or not at all and the power steering gets jerky, unless the engine speed is very high. Everything works fine from when I start the tractor up to that point. I have replaced the deteriorated hydraulic hoses between the hyd. pump and the reservoir and the oil cooler and I have cleaned the oil cooler fins, but the problem continues. The loader control valve(s) and one side of the 3-point lift shaft seem to be leaking some hydraulic oil and I need to add hydraulic oiI periodically to maintain the proper oil level. The oil on the dipstick appears clean, has normal odor, but sometimes has a few air bubbles in it. Can anyone recommend next steps to troubleshoot and fix this problem?

Sincerely,
Kevin




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Hydraulic Problem - John Deere 2750

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PaulChristenson
Join Date: Dec 2007
Posts: 83 Vermont
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2016-02-21          194578


Have you actually pulled and cleaned the hydraulic filter? ....


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Hydraulic Problem - John Deere 2750

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Imfedup
Join Date: Dec 2015
Posts: 58 Central Kentucky
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2016-02-21          194581


The condition of the suction screen and filter are always suspect, but usually create problems with cold oil, and not so much after an hour or more of use. What you describe is more often the result of internal leaks somewhere within the system. The three point piston seals or control valves are fairly common. Also piston seal leakage in PTO, hi/lo, or other hydraulic clutch packs can be a factor, as well as the internal steel tubes supplying flow to these and other components. The remote valves, loader valves as well. There are some general trouble shooting guidelines for determining such leaks. Lift system leaks can often be seen as fluid running down or spraying under the lift cylinder and down the right side of same as viewed through the hyd filler opening with a flashlight. The remote, loader, and steering valves can be isolated one at a time and the supply ports capped off or plugged. If removing one or more of them from operation allows the rest of the systems to function properly, then problems can be isolated. ....


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Hydraulic Problem - John Deere 2750

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kthompson
Join Date: Oct 2005
Posts: 5275 South Carolina
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2016-02-22          194584


"imfedup" like your handle there.

....


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Hydraulic Problem - John Deere 2750

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KevinsJD
Join Date: Feb 2016
Posts: 5 Virginia
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2016-02-22          194592


Paul, no I have purchased the replacement filters, but not replaced them or cleaned the suction filter screen yet (I'm recovering from back surgery). Do you think I should do this first before trying to locate and fix the leaks? ....


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Hydraulic Problem - John Deere 2750

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PaulChristenson
Join Date: Dec 2007
Posts: 83 Vermont
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2016-02-22          194593


Cleaning/replacing the hydraulic filter if it's really gunked up...might solve you problem with one action...:) ....


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Hydraulic Problem - John Deere 2750

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KevinsJD
Join Date: Feb 2016
Posts: 5 Virginia
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2016-02-22          194594


Imfedup,
Thanks for the advice. You've suggested many possibilities. Can you recommend an order for the things to try? ....


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Hydraulic Problem - John Deere 2750

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jdgreen
Join Date: Jul 2003
Posts: 232 Maryland
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2016-02-22          194595


My suggestion would be to change the filter and clean the sump screen first. I agree with Imfedup, that filters usually cause more problems with cold oil, but sometimes debris will fall off of filters when oil flow stops, and hydraulics work better for a while until debris is sucked back into the filter. After that, I would suggest to start tractor and leave it sit and run for maybe 15 or 20 minutes without using any hydraulic functions. Then feel the hydraulic components with your hands to feel for heat. Internal leaks in the high pressure circuits will cause heat build up. Feel the pump, steering valve, selective control valves and the rockshaft housing, especially the just in front of the seat bracket and on the right side. If none of the high pressure components heat up noticeably, then chances are good you have an internal transmission leak. Are you always using the pto when hydraulics quit working? If so, try turning the pto off and see if hydraulics improve after about a minute. ZDOes your tractor have a hi-lo lever on left side of dash? If so, try running in lo and see if hydraulics quit, if so then shift to hi and see if hydraulics return. ANother place to look is the filter relief valve. It is located above the hydraulic filter housing. It needs a 1 1/4" wrench to remove the plug to access the valve. The cartridge slides out after removing the plug using a magnet or needle nose pliers. Check to see if a piece of dirt is holding the valve partially open. ....


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Imfedup
Join Date: Dec 2015
Posts: 58 Central Kentucky
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2016-02-22          194597


All good advise. Be aware that checking/cleaning the suction screen involves draining the hydraulic system. If you're going that far, you might consider replacing the load shaft seals. They are a common failure over time and will go from a slight seepage to a steady drip in a short time. Not expensive, and easy to replace, particularly while the housing is empty. ....


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KevinsJD
Join Date: Feb 2016
Posts: 5 Virginia
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2016-02-23          194600


Many thanks to all of you for your advice! :) Here's my plan:
1. Start tractor, let run for 15-20 minutes without using hyd. functions and feel for warm/hot components.
2. Run the tractor with bush hog until the problem occurs, then turn-off PTO and see if hydraulic function returns. Try shifting between Hi/Lo on transmission lever and see if hydraulic function changes.
3. Drain the hydraulic oil and remove filters, suction screen and filter relief valve. Clean suction screen and make sure relief valve can fully close. Reinstall valve and install new filters.
4. Replace the 3-pt. load shaft seals. Should I use standard JD replacement seals or is there a better after-market design available? Any special tools needed? How much shaft wear at the seals is acceptable?

Unfortunately, I may be a month or two before I get to this as I'm recovering from back surgery, but I will let you know how it works out. In the meantime, please let me know if anything else comes to mind. ....


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