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10K and Climbin!
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Discussion Starter · #1 ·
My neigbor's JD 750 is acting up.. As I'm not really well versed in the CUT's I'd like to lean on you folks a bit.. He changed the fluid due to it is milky white.. He then had trouble with the hydralics since refilling. we tried lifting the bucket with my tractor and opening/closing valves but it just seems like it is starving for fluid & cavitating. once the pump primes it does move a bit but then it starves again and win't move anything.. I drained the fluid again and it is still milky white:banghead3 I pulled the sump line off the pump and tranny to see if there is a plugged screen but nothing is evident there?? What am I missing??:dunno:
 

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A few quick questions...

Does he let the tractor idle for a long while before moving anything? I don't have the 750 service manual on hand, but some tractor's priming instructions include running at idle for 10-15 minutes and then high idle for 10 more minutes. By then the cavitation should disappear. After that, the instructions can be very specific to properly prime the system.

Did he replace the fluid with anything other than JD recommended hydro fluid?
 

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I Love All Color Tractors
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The type of fluid used was my first question too. The X50 series are particularly sensitive to the type of fluid used and the viscosity really matters. In the colder climates, like New York and in the climate that I have here, the low viscosity Hy-Gard fluid makes a world of difference.
 

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10K and Climbin!
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Discussion Starter · #4 · (Edited)
Re: JD 750 Hydro Trouble

The fluid is 20W hygard and the thing was run for quite a while.. As the pump's pickup tube & pump position is quite a bit higher than the tranny sump I was thinking to try & put a little air pressure @ the fill port to force some more oil into the sump line up to the pump or even jack the back of the tractor up to reduce the altitude or distance the pump needs to pull the fluid into the pump. As I have the line off the pump I may just reassemble the bottom connection and try the air to get oil to fill the supply line then reassemble the supply line to pump connection and restart the thing.. :dunno:


Once oil is in the pump it works well but then it loses prime and then nothing works..:banghead3 I don't want to toast the pump due to lack of oil and need to get this thing going for his so it will be ready for the winter season as he uses it for his driveway.. We left the thing running many minutes many times today so if it was going to prime it would have..

:thanku: for the replies..
 

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I Love All Color Tractors
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Does this tractor have a screw on filter between the sump tube and the hard line going to the pump?

One problem that I've had on my 950 in the past with this filter setup is the rubber line between the screw on filter and the pump has a little twist in it, the pump can pull it closed and shut off the oil flow.
 

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10K and Climbin!
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Discussion Starter · #6 ·
Nope- No filter.. nice try.. I was combing the thing looking all over trying to find one but it doesn't.. It just doesn't pull the darn fluid up the darn 15"-18" tubing rise..:banghead3
 

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I Love All Color Tractors
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WOW! That much lift? The lift on mine is around four or five inches. Of course, horizontally, we're talking several feet of travel.

Alright, another try. Does this machine have power steering? If so, does it have a little black box on the left hand side of the machine below the driver's seat? There is a diverter valve in there that has a really tiny orifice that might have something caught in it, restricting fluid flow to every part of the tractor. Again, it's happened on mine.
 

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I Love All Color Tractors
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If the machine has power steering, the black box should look something like this one. Forgive the oil mess, I was having some serious hydraulic problems and hadn't cleaned up yet.

General Location:



Closer Look:



The diverter valve that I'm talking about screws into the back of the box. Don't confuse it with the one sticking out of the top of the box seen above. That one is the pressure relief valve. This is what the diverter valve looks like removed:



What I found in mine:





Hope this helps. If not, well, it's strike two for me. :D
 

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10K and Climbin!
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Discussion Starter · #10 ·
I've been researching the web for help with this problem and have heard repeadtedly about a screen that plugs up and kills the pump supply.. I found a service manual and am D/Loading it as I speak here so I'll report back with my results..
 

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10K and Climbin!
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Discussion Starter · #11 ·
Aha!! The sump screen was pluuuuuuuuggggggeeeedddddd! :fing20: :eck16:

I read through the 750 bible I D/Loaded after like 30 minutes and lo & behold there is a screen in the tranny on the other side of tranny from the the supply line.. I removed it and cleaned tons of nasty, grimy, dirty, filthy junk out of it and replaced it.

Once I refilled the tranny & started the thing the pump picked right up!!

It's a miracle!! :dancingpa

So- all you 750 owners (650's too!) Here's a clip out of the destructions to help you find the offending screen.. (normal maint directs it to be cleaned @ 600 hours..) Now I gotta find something else to work on.. :trink40:
 

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Simple fixes are nice! :thThumbsU
 

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"Now I gotta find something else to work on.. "



You could go to VA and help my nephew.

His JD will turn over but not start!!

Soil Tractor Agricultural machinery Vehicle Automotive tire
 

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10K and Climbin!
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Discussion Starter · #14 ·
"You could go to VA and help my nephew.

His JD will turn over but not start!!

Yup- Looks like it turns right over CP! :banghead3 Hope he didn't spill his 'coffee'!

You may want to pull the injectors or glo plugs and empty the oil out of the cylinders.. :banghead3 It shoots out pretty good for a few rotations.. :thSick:

I'm sending the manual over to the neighbors on a zip drive so he can read all of the info he needs about that thing.. (796 pages worth!) :trink40:
 

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I pulled the sump line off the pump and tranny to see if there is a plugged screen but nothing is evident there?? What am I missing??:dunno:
Man,

Sorry I didn't re-read your first post... I assumed you already checked the filter screen. Glad you got it goin! The screens aren't cheap but the protection they provide can save you big time.:fing32:

Also... it may be easier to just replace the screen with a new one. They can be very fragile especially where it's welded together.
 

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I Love All Color Tractors
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Man,

Sorry I didn't re-read your first post... I assumed you already checked the filter screen. Glad you got it goin!
I'm right there with you, Bob.

When I read the first post saying that oil was just changed, I assumed that the screen was pulled when the sump was drained. That's what we get for assuming.

Great to hear that you got it going though, WNY. I'm just sorry that I wasn't any better help to you. Sometimes it's the obvious that escapes us. :banghead3
 

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10K and Climbin!
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Discussion Starter · #17 ·
I'm right there with you, Bob.

When I read the first post saying that oil was just changed, I assumed that the screen was pulled when the sump was drained. That's what we get for assuming.

Great to hear that you got it going though, WNY. I'm just sorry that I wasn't any better help to you. Sometimes it's the obvious that escapes us. :banghead3
Yeah- I guess I'm spoiled by / used to external filters.. I haven't worked on the CUT's much.. It just acted like a starved pump.. :banghead3

As I wasn't the one that changed it and wasn't familiar with that machine it was a head-scratcher.. I had looked @ the cover and wondered the first day.. Guess I shoulda pulled it off after looking @ it. :fing20:
:thanku:Thanks for your help guys!
 

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No Bozo's
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A couple of questions.

First, where in WNY? That's where I am along with my 650 and 750 and a couple others.

Second, how can I get a copy of the 750 manual? I've been lucky so far with both of the JD's, but I know it's only a matter of time before I run into a problem that'll require a book.
 

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A couple of questions.

First, where in WNY? That's where I am along with my 650 and 750 and a couple others.

Second, how can I get a copy of the 750 manual? I've been lucky so far with both of the JD's, but I know it's only a matter of time before I run into a problem that'll require a book.
I got my shop manual by going to techpubs.deere.com. Look under tech publications. Enter TM1242 in the keyword or pub. # box. The shop manual is available as a book $150 and on CD rom for $75. I ordered the CD and it was here in a couple days. (I just take my laptop over to the shop). The manual is for both the 650 and 750. A bargain for you!!! over 600 pages. Very well written. It's all black and white, but has about every spec you'll ever need. JD takes the time to explain major functions, such as hydraulics, fuel and coolant systems, (with color to show flow directions) just to name a few. Reads like .pdf files. I found it to be handy on the laptop, as you can scroll up and down as you work. Had to split my tractor once to replace broken parts on the 4WD shift lever. Put a piece of seran wrap over the keys and your good to go. No oily paper pages...
 
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