Ford 600 3-point hydraulics problem

karman1970

New User
Hi all. Just bought my first tractor a few weeks ago. Ford 640, not sure of the year but I think it's a fairly early model.

It came with a Bush Hog when I bought it. Used it few times in the evenings after work to cut my pasture. No issues. First Saturday rolls around so I had all day to use it. Only thing I noticed when I first pulled it out of the barn to check fluids was that the I had the Bush Hog up in the air with everything shut off and it just dropped a couple inches out of nowhere. Kind of startled me, but I didn't think much of it. A couple hours later, I look behind me and the Bush Hog has all of a sudden dropped, so the front edges are digging into the ground. I stopped and tried to get it to pick up, but it won't do anything. Finally gave up and went inside to do some research. I went back out 30 minutes or so later and got it to pick up, but it only made it half way back to the barn before it dropped again. Had to wait a while again. Got to the barn and did some poking around. Check the pump, still seems to have prime. I noticed the arms were bouncing or "hiccupping". Looked through the fill hole and didn't see any leaks. Figured time to tear into the lift. First things I noticed when I got it apart were A) very grungy and looked like corrosion and rust, must have gotten moisture in it at some point B) measured the linkage and found it out of adjustment and it runs out of adjustment to get everything in spec. Decided to do a complete tear-down, which leads me to some questions on what I do and don't need to replace.

Here is the cam on the lift arm. I don't have a new one to reference, but it looks worn and flat-spotted in the middle. It also looks like someone may have tried to weld or braze a new surface on it. The dowel that rides on the cam also looks like someone put a little brazing on it. I haven't been able to get the lift arm off yet, but I think with my press and a torch I might be able if need be. I don't think I'll be using draft control all that much, so does it really matter if the cam isn't perfect, or will it prevent me from getting the linkage adjusted?

Next is the plate the draft rod rests against. I've heard it's impossible to get the linkage adjusted right if this is worn, as well. Think this needs to be replaced? If so, is it necessary to get one with the pin?

Finally, the cylinder and piston themselves. I didn't see any leaks when it was trying to diagnose the bounce. Got the piston out today and there looks like maybe some corrosion from moisture on couple spots of the piston. There are matching spots on the cylinder, which makes me think it maybe sat for a long time at some point. Also, there is some scoring on the cylinder and the piston. The ones on the piston are very light - I can only catch my finger nail on one. Any advice here? Will it be okay like this or do I need to try and clean up and polish the surfaces or do I need to get some replacements? Piston isn't a big deal, but it would be nice to avoid having to buy a new cylinder if I can avoid it.

Thanks in advance for any assistance!
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I would grind the cam and cam pin into
the correct shape as best as possible or
replace the pin. Get all of the rust
off and paint it with a light coat of
rustolium and make sure you do not get
any paint on the valves. Put a new o-
ring and leather washer on the piston
after using 600 or 800 grit on the
piston to clean it off.
Same for the cylinder to clean up the
scratches as best as possible. Take out
the control valve and make sure it is
clean and reinstall it. Then set the
linkage to the correct settings. Put
all new fluid in. Then try it to see if
all works as it should.
 
Looks like you will also need a new draft control spring plate or rebuild that one, you can get those for about 15 bucks here on
this site. Like you, I have heard you'll never get proper adjustment without that being correct. Just curious..where are you
measuring from, the retaining plate or valve housing? Also have you set the lift arms the 1/2 inch up from completely lowered?
Don't mess with that old cam pin, drive it out and get a new one if you can. Good luck...that is one rusty fellow.
 
One other thing to look at part #nca540a...draft control mounting fork, they say if hat is bent it will be hard to adjust properly.
 
(quoted from post at 14:46:00 09/03/17) Looks like you will also need a new draft control spring plate or rebuild that one, you can get those for about 15 bucks here on
this site. Like you, I have heard you'll never get proper adjustment without that being correct. Just curious..where are you
measuring from, the retaining plate or valve housing? Also have you set the lift arms the 1/2 inch up from completely lowered?
Don't mess with that old cam pin, drive it out and get a new one if you can. Good luck...that is one rusty fellow.

The retaining plate, I think. But now that you bring it up, I'm not sure. I have had the lift arms 1/2" up. I'll try to get that pin out. Pretty corroded. Got it soaking in oil right now. I suppose I'll try to patch up what I can, button it back up, and see if she'll work half-way decent. If not, I'll at least have a list of replacements to start ordering Tuesday.

Thanks for the advice.
 
(quoted from post at 22:46:00 09/03/17) Looks like you will also need a new draft control spring plate or rebuild that one, you can get those for about 15 bucks here on
this site. Like you, I have heard you'll never get proper adjustment without that being correct. Just curious..where are you
measuring from, the retaining plate or valve housing? Also have you set the lift arms the 1/2 inch up from completely lowered?
Don't mess with that old cam pin, drive it out and get a new one if you can. Good luck...that is one rusty fellow.
I would like to know how to do the measurements and how you position the arms without that special tool ?
 
D. Prater... I'm hesitant to even chime in here because I'm by no means an expert but, I just finished one on my 641 and it came out pretty well. I mounted the lift cover in a vise with the draft spring up, ran a 1/2 inch bar (I used all thread) through the ends on the lift arms and then raised it up until it touches the draft spring, then lock the arms down with the cap screws on the end of the arms. This should give you the 1/2" up from the extreme lowered position the manual requires. Now the next question will be, where to do the measuring...I believe it has to be done from the surface of the lift cylinder not the retaining plate. I'm hoping one of the gurus will step in here to either confirm that or correct that. I had a badly worn spring mounting plate but was able to shim it with a 5/8" washer, that did the trick and the adjustment was easy after that. Hope this is what you were after.
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