John Deere 750 with loader

[matoyan]

I bought the tractor and I was able to get bush hog, a post hole digger, and a box blade for a REALLY good price. Now I need to get the hydraulics figured out. It does have power steering but not workind since it has no hydraulics power at all. I checked the fluid level, the filter and fluid was changed in the summer (according to the pervious owner) and the screen cleaned. what can I check next? How do I check to see if the pump is working? the stop valve is rusted in place so I can't turn it on/off. I know when I take the dipstick out to check hydraulic fluid level, it makes a sound of sucking air like it's breaking a seal. Like a vacuum was created and i'm releasing the pressure. The loader does not move up or down. Any suggestion would be great.

 

[paulharvey]

Im no hydralic expert, but.on my Kubota when I drained the hydralic system to clean screen/change oil, I.had similar problem. I looseened the pillow block on preasure line to the 3 pt freeing up the system, blowing air out of lines and basically allowing oil to flow. Only major down side, I wasnt expectinh to get an oil bath, and hydro got in my beer. Some be careful, set the beer a few feet away.

No idea if your problem is same, but something cheap to check, and the fact he replaced the oil means he had drained when he did.

 

[matoyan]

thanks paulharvey, but what is it and where is it? All I have is the owner's manual and I need to buy a service manual.

 

[moship]

Given hydraulic fliuid for this tractor is relatively cheap, I'd drain the fluid and doube check the screen and purchase a new hydraulic filter just to verify everything is clean and OK. Maybe the wrong fluid was used (this would be a very long shot, and more likely if it was hydostatics issue,but yours is gear drive). For the record I never remember mine making a sucking noise when the yellow fill plug was removed while running. Is the fluid level correct?

Does the power steering work? Mine seemed to be overly boosted meaning it was very easy to turn. I would have liked it to be a little less, so more fluid would be routed to the FEL or 3-pt hydraulics. Perhaps the diverter valve located on the starter side of the firewall is the issue. Since PS and FEL hydraulics are shared the diverter valve seperates the flow proportionally between the two hydraulic circuits. I personally think this i a very long shot though...

The manual is well worth the cost. It has very detailed photos for each major step and contains color coded schematics of the hydraulic circuits. I gave mine away when I sold the tractor.

How about checking hydraulic pressure to see if it is OK. Perhaps the relief valve is stuck open and simply bypassing most of the fluid back to the reservoir. Maybe run a flow test by timing how long it takes to pump a gallon or so. (be very careful with high pressure fluid)

Some basic flow & pressure tests will help in finding the problem.

Keep everyone posted on the progress.

 

[paulharvey]

I dont know on the JD, but if you follow your hydralic line back you should at least find a screw in fitting that could be CRACKED just a hair with machine running until you get a Drip of oil, dont take it all the way loose, or youll find out how much hydro can really come out in the split second your trying to shut things down. If you get no oil comeing out the that means you either have a blockage somewhere up stream (ie between pump and fitting), you have a bad pump, or your pump is starving for oil (blockage in low preasure line from resevoir to pump).

If you dont get oil, move up stream till you final do. Feel your pump as you work, if its blocked it can get hot and destroy Orings if you keep running it, like running a pump or preasure washer "dry".

Be careful, and dont put you hands around the fittings, because there are hazards to getting 2000 psi of oil in your hand.

 

[matoyan]

Anyone have a used 750 service manual cheap? Where is the screen located at?

 

[moship]

A picture of the screen might be in owners manual if you have it. Another place to check is online with JD parts. I believe you have to register to display the parts drawings. This would at least give you some idea where it is located.

Given where the hydaulic filter is located I'd check to make certain it isn't bent or damaged in any way that might be causing your problem. It should set parallel with the ground. I think the screen is located on the side of the rear. If the right hand side tire was removed it would be seen... At least this is what I think. Then again it might be removed when the filter assembly is installed for the power steering.

I wish I could remember more specific details to be able to help out more definitively.

 

[paulharvey]

Removed, thought I had a wensite for you but it had no Jd 750

 

[moship]

Here's the link to the JD website for parts... John Deere - Parts Catalog
Model Search: 750 A bunch will come up, just look for the compact tractor one

Under "Alphabetical List" Look under the T's for Transmission Oil Filter 750. There is a picture of the filter screen and perhaps there is enough clue to help find it's location.

I wanted to post an XPS file of the parts drawing, but it not allowed. Send a private message with your email and I'll send it to you.

 

[matoyan]

After talking to a JD service shop and him telling me that it cost $70 an hour to diagnose the problem, I decided to go and check out the screen. To my suprise, the guy had never cleaned it. It was full of gunk! I replaced the fluid, filter, and cleaned the screen and the hydraulics are working perfectly. Thanks for everyones help.