640 3 point slow

Montana55

Member
I am trying to figure out the hydraulics on this tractor. I'm using it for a back blade and landscape rake, but the speed of the 3 point is extremely slow. I put a kit in the pump a couple years ago, but no noticeable improvement, no worn parts detected.

I'm running hy-tran oil in the reservoir, it's about 35 degrees F and currently using a very heavy 8' back blade. I don't really understand the 3 positions of the selector lever, but have been using the middle (horizontal) position.
If I lift the implement, it does not leak down overnight. It's just pathetically slow to move, both up and down. The lifting arm movement seems minimal to me. Is there a filter somewhere? I have been reading a manual but it confuses me more than anything. Troubleshooting section does not mention the symptoms I'm having. It does mention bleeding the pump, but I haven't been able to figure out how, is there a port somewhere?
 
The hydraulic oil is clear and the lever correct. I removed the fill plug and looked inside with a flashlight and worked the selector lever and touch control lever to see if there was any slop in the connections, but everything looked good to my eyes. The hydraulic pump is the wobble shaft type with 4 allen plugs on top. Is one of them where you bleed the pump?
Also noticed that if I rev the motor and raise the implement as far as it will go, I can lift it farther by hand and it will stay.
Any suggestions?
 
I connected a hydraulic test gauge on the pump. First I tried the right front port on the center section like the manual says, but got no reading when I raised the 3 point. Then I connected it to the right front port on the front casting and it reads about 400 PSI at idle and about 700 PSI at full RPM with the selector lever in the horizontal position and the touch control all the way up as pictured.
cvphoto6461.jpg
 
(quoted from post at 13:42:51 02/26/20) I connected a hydraulic test gauge on the pump. First I tried the right front port on the center section like the manual says, but got no reading when I raised the 3 point. Then I connected it to the right front port on the front casting and it reads about 400 PSI at idle and about 700 PSI at full RPM with the selector lever in the horizontal position and the touch control all the way up as pictured.
<img src="https://www.yesterdaystractors.com/cvphotos/cvphoto6461.jpg">
ressure is proportional to load being lifted. chain arms down & you should see around 2,000psi
 
(quoted from post at 11:57:37 02/27/20) Thanks for the tip, JMOR! I chained down the lifting arms and got 830 PSI.
ounds like a leak somewhere (cyl/piston greatest suspects) or faulty pump.
 
(quoted from post at 11:56:08 02/27/20)
(quoted from post at 11:57:37 02/27/20) Thanks for the tip, JMOR! I chained down the lifting arms and got 830 PSI.
ounds like a leak somewhere (cyl/piston greatest suspects) or faulty pump.
hanks, JMOR. It will hold a heavy implement off the ground a couple days at least, so I figured the cylinder was probably OK. Maybe I didn't know what I was doing when I rebuilt the pump. Do you think a relief valve would cause that?
mvphoto49935.jpg
 
(quoted from post at 17:50:05 02/27/20)
(quoted from post at 11:56:08 02/27/20)
(quoted from post at 11:57:37 02/27/20) Thanks for the tip, JMOR! I chained down the lifting arms and got 830 PSI.
ounds like a leak somewhere (cyl/piston greatest suspects) or faulty pump.
hanks, JMOR. It will hold a heavy implement off the ground a couple days at least, so I figured the cylinder was probably OK. Maybe I didn't know what I was doing when I rebuilt the pump. Do you think a relief valve would cause that?
mvphoto49935.jpg
ot the ram cyl safety relief or it wouldn't hold for days,, but the over pressure relief could cause that.
 
(quoted from post at 19:15:07 02/27/20)
(quoted from post at 17:50:05 02/27/20)
(quoted from post at 11:56:08 02/27/20)
(quoted from post at 11:57:37 02/27/20) Thanks for the tip, JMOR! I chained down the lifting arms and got 830 PSI.
ounds like a leak somewhere (cyl/piston greatest suspects) or faulty pump.
hanks, JMOR. It will hold a heavy implement off the ground a couple days at least, so I figured the cylinder was probably OK. Maybe I didn't know what I was doing when I rebuilt the pump. Do you think a relief valve would cause that?
mvphoto49935.jpg
ot the ram cyl safety relief or it wouldn't hold for days,, but the over pressure relief could cause that.
lso, there are pictures floating around which show incorrect assembly of the over pressure relief valve.
 
Thanks, JMOR. I pulled the relief valve at the bottom of the rear housing and found it had a broken spring. That must be my problem. I'll see if I can find a new one.
 
Well. I replaced the over-pressure relief valve on the bottom. I thought for sure this would cure the problem because the spring was broken, but low and behold it didn't make a bit of difference. It still only gets up to 850 PSI when the arms are chained down.
The 3 point still works, goes up and down, stays up when I leave it, but slow and low pressure.
Is there anything else to check before I take the pump back off?
 
Since it holds in up position, I can't think of anything else unless you are dumping fluid from hyd system. That would usually be rusted tube passing thru transmission and will exhibit itself as overfull/overflowing transmission and loss of fluid from hyd reservoir. You can eliminate everything under top cover by moving accessory plate to block off pressure line coming from pump.
SPB82ug.jpg
 
Thanks, JMOR.
There are no issues with levels, I tried blocking off the port as shown in your pics, but no difference in hydraulic pressure with lifting arms chained down.
I removed and disassembled the piston pump again, but I don't see anything wrong with it. I poured kerosene in the intake and discharge ports with balls in place, one of the discharge ports leaks down after a few minutes. I did not remove the plate from the discharge end because I don't have any spare gaskets.
When I tested the intake valves, I just placed the balls in the ports, gravity seal, since there is no way (that I know of) to test them with the springs in place. A couple of them leak down after a few minutes.
This is a 6 piston positive displacement pump. I don't see how there could be a loss of pressure unless all 6 were compromised. If the very minor leakage I see is significant enough to be a problem it would reduce the volume not the pressure, right?
Cornfused here. What else should I be looking for?
 
(quoted from post at 19:36:16 03/04/20) Thanks, JMOR.
There are no issues with levels, I tried blocking off the port as shown in your pics, but no difference in hydraulic pressure with lifting arms chained down.
I removed and disassembled the piston pump again, but I don't see anything wrong with it. I poured kerosene in the intake and discharge ports with balls in place, one of the discharge ports leaks down after a few minutes. I did not remove the plate from the discharge end because I don't have any spare gaskets.
When I tested the intake valves, I just placed the balls in the ports, gravity seal, since there is no way (that I know of) to test them with the springs in place. A couple of them leak down after a few minutes.
This is a 6 piston positive displacement pump. I don't see how there could be a loss of pressure unless all 6 were compromised. If the very minor leakage I see is significant enough to be a problem it would reduce the volume not the pressure, right?
Cornfused here. What else should I be looking for?
ith the plate moved to block high pressure line/port, there is no need to chain lift arms, as nothing is remaining in circuit other than pump, horizontal line to rear, over pressure valve and the vertical tube up to the now blocked port. You seem to have verified all but the vertical tube. Might try to see it? Or spray from it?
 
Thanks, JMOR.
How can I see that vertical tube? Do I pull the lift cover and block the port again? Or pull it out and replace O rings? I can't find a picture of it in the manual.
 
(quoted from post at 22:01:51 03/04/20) Thanks, JMOR.
How can I see that vertical tube? Do I pull the lift cover and block the port again? Or pull it out and replace O rings? I can't find a picture of it in the manual.
aybe thru fill plug, PTO lever cover, mirror, light, ....?
 
I started re-assembling the hydraulic pump and discovered something interesting. There are no intake valve seats in it! Amazing what you find when you put on your reading glasses. The balls were in the holes where the seats should be and actually managed to produce 800 PSI without seats! I suppose it's been like this for ages. When I put a kit in it 2 years ago, I did not remove or replace the seats and I still have them.
One question: Is it normal for the seats to fit loosely? 4 of them fall out when I turn the housing upside down. They were in all the way. Seems like they wouldn't seal unless they are an interference fit.
 
(quoted from post at 20:12:10 03/06/20) I started re-assembling the hydraulic pump and discovered something interesting. There are no intake valve seats in it! Amazing what you find when you put on your reading glasses. The balls were in the holes where the seats should be and actually managed to produce 800 PSI without seats! I suppose it's been like this for ages. When I put a kit in it 2 years ago, I did not remove or replace the seats and I still have them.
One question: Is it normal for the seats to fit loosely? 4 of them fall out when I turn the housing upside down. They were in all the way. Seems like they wouldn't seal unless they are an interference fit.
, too expect interference fit, but maybe someone else will answer definitively, as I can't with absolute certainty, but seem to remember needing a puller or improvised puller to remove them?
 
Well I got the parts for the hydraulic pump and put it back together. Started it up and it primed quickly. It still will not reach pressure, only showing about 600 PSI with lifting arms chaned down. I removed the PTO lever side cover and looked in there and I see a steady stream of oil shooting upwards from where the (brand new) over-pressure relief valve is. The new relief valve had a gob of epoxy or something in the end of it apparently to prevent anyone from changing the pressure after it was factory preset. Do you think my new relief valve is defective?.
 
I sent the relief valve back and just received the new one today and put it in. Before I put it in the case, I got underneath the tractor and looked up in the vertical bore where the overpressure relief valve goes to see if the case has some kind of defect preventing the O ring from sealing, but could not visibly see anything wrong with it.
Anyway, I still can't get more than about 800 PSI and I still see a fountain of oil directly above where that relief valve is, while running with lifting arms chained down.
Since the fountain of oil is a couple inches forward of where the vertical tubes are, I don't think the tubes are defective (?).

I'm stumped. I can't find a drawing in my repair manual showing the oil passageways in the case there. Any ideas?
 
I don't know those passage ways either. You may learn something about them by thinking about openings that factory used to drill. For example, coming from the tubes fed by pump & entering the area in question, they would have drilled into the casting front, heading rearward. Then up, probably thru the relief valve hole & maybe near/beside that for connection to vertical tube going up to top cover , both suction & pressure. There is a plug closing a drill passage path in the bottom in this area and another in the side near drain plug for same drilling purpose. Only pix I have of this area doesn't show much except the discharge tube /opening for flow during lower & unloading from pump when not lifting. What is possibility of water/condensation collecting in this area & freezing , resulting in a crack in casting?
0hTRkor.jpg
 
Thanks for the reply JMOR. The theory about freeze damage makes sense. It has been sluggish like this ever since I bought it years ago. I will probably close it up and operate it as is for now to get some work done.
What gets me about the fountain of oil is that it is directly above the relief valve, perfectly round mushroom flow of oil spraying straight up. Seems like it's coming straight up from the bore that the relief valve lives in.
To me, this seems like exactly what the relief valve should do when it relieves pressure.
 
Well, I seldom guess, but I'll go out on a limb here & make a educated-guess. :) I expect that since I can't see top of relief valve, that the dump from it exits at hole marked by red arrow.
ELFdemH.jpg

gc60z5C.jpg
 
I don't know. When I looked in the bore the relief valve lives in, I could see all the way thru, in other words the top is not plugged.
Both of the O rings on the valve are low and it's discharge holes are above the top O ring.
mvphoto52944.jpg
 
(quoted from post at 19:49:23 04/17/20) I don't know. When I looked in the bore the relief valve lives in, I could see all the way thru, in other words the top is not plugged.
Both of the O rings on the valve are low and it's discharge holes are above the top O ring.
mvphoto52944.jpg
nteresting, but I'm about out of gas. Let us all know when you know more.
 
I finally got back on this project. I pulled the relief valve again and chiseled out the epoxy seal and screwed the adjuster in 3 turns. Put back together and filled hydraulic. Now I get 1100 PSI with the lifting arms chained down! An increase of 300 PSI.

So, I drained the hydraulic and pulled the relief valve again and screwed it in another 3 turns. It felt like it bottomed out. Put back together and only had an increase of 100 PSI.
So I pulled relief valve again and disassembled it, compared parts to the old one (see pics). One potential problem is the aftermarket valve has a pointed and knurled setscrew instead of a flat-faced adjuster like the original. Another problem is the aftermarket inner screw appears to be bottomed out. You can see in the pic that it's distorted from me trying to make the final adjustment.

So I will use the aftermarket main body, ball and outer spring with the original adjustment screw and inner spring, which has one coil broken off.

So far I have drained and refilled the hydraulic system 7 or 8 times.


mvphoto54603.jpg


mvphoto54604.jpg


mvphoto54605.jpg
 
(quoted from post at 11:34:17 05/10/20) I finally got back on this project. I pulled the relief valve again and chiseled out the epoxy seal and screwed the adjuster in 3 turns. Put back together and filled hydraulic. Now I get 1100 PSI with the lifting arms chained down! An increase of 300 PSI.

So, I drained the hydraulic and pulled the relief valve again and screwed it in another 3 turns. It felt like it bottomed out. Put back together and only had an increase of 100 PSI.
So I pulled relief valve again and disassembled it, compared parts to the old one (see pics). One potential problem is the aftermarket valve has a pointed and knurled setscrew instead of a flat-faced adjuster like the original. Another problem is the aftermarket inner screw appears to be bottomed out. You can see in the pic that it's distorted from me trying to make the final adjustment.

So I will use the aftermarket main body, ball and outer spring with the original adjustment screw and inner spring, which has one coil broken off.

So far I have drained and refilled the hydraulic system 7 or 8 times.


mvphoto54603.jpg


mvphoto54604.jpg


mvphoto54605.jpg
lad to see you making progress. Great perseverance! Can you get a good picture down in the hyd compartment where the oil stream was coming from?
 
If I pull the side cover again I'll take a pic.
I put the now modified relief valve back in. Since I'm starting from a fresh reference point, I got 1100 PSI on the first try. Pulled and cranked the adjustment in another 1 1/2 turns, felt bottomed out. Tried again, only 1150 PSI.
I'm really getting tired of draining and refilling hydraulic oil. I think what I'll do next is fill the original relief valve with JB Weld epoxy to completely block all internal passageways. and see what kind of pressure that might develop. If that brings it up to near 2000 PSI, I'll look for another source for a relief valve.
Operationally, 1100 PSI is a significant improvement over 800.
 
(quoted from post at 17:58:18 05/10/20) Will be interesting to see where this story ends. Hope well!
opefully it does end....any year now! LOL!

I filled the original relief valve with epoxy and put new O rings on it, put back together, filled with oil and tried it......still only around 1100 PSI. Here is a pic of the oil shooting up from the refief valve area.
 
Hard to tellwhat I'm looking at... all that in green is what? Maybe the yellow? What is W?

SZnF3Q0.jpg

having difficulty relating to this:
gc60z5C.jpg
 
(quoted from post at 16:04:57 05/12/20) Don't know about the yellow. The green is the fountain of oil. W is one of the vertical pipes.
OW! That is a large stream! You might feel around and try to isolate the source before draining all the oil, BUT, if you do, BE VERY CAREFUL , as I have heard of high pressure fluids penetrating human flesh.
 
(quoted from post at 14:59:38 05/12/20) However, I seldom violate my rule of "don't put hand in any place you can't see".
hat explains why you work on antique tractors instead of modern vehicles. On the latter you can usually see it and you can feel it but you can't see it and feel it at the same time. :x

Ok I stuck my fangers in there with it running and the oil is coming out just behind the front wall of the housing (casting). There is no hole large enough to stick a finger in, it's just shooting straight out of something....the casting I guess. From the feel of it, it seems like the hole is 1/8" wide and 1/4" long I guess. I've been looking at the pics you posted but they don't show the exact location where the oil is coming from. What is there between where the pressure line comes in and the relief valve?

I guess I will drain it and remove the lift cover and see what I can see.
 
Looks like just pressure & suction passages. Looking like you may find freeze damage the we talked about earlier. :(
cmiFlOP.jpg
 
Thanks for the info, JMOR. Do you know why there are two O rings shown (#93)? The relief valve only takes one small and one large O ring.
 
Thanks, JMOR.
I stuck my hand in there again and ran at lower RPM's....I think it's leaking where the horizontal pressure pipe connects to the differential housing, then spurting up the gasket area where the dif housing and trans housing mate.

I think I'll button her back up and plan on doing this job next winter. Is it difficult?
 
(quoted from post at 18:03:43 05/13/20) Thanks, JMOR.
I stuck my hand in there again and ran at lower RPM's....I think it's leaking where the horizontal pressure pipe connects to the differential housing, then spurting up the gasket area where the dif housing and trans housing mate.

I think I'll button her back up and plan on doing this job next winter. Is it difficult?
have not done that split. Maybe someone will chime in that has.
 
Just an update. I replaced the O rings at the split and re-adjusted the relief valve and now I have 2000 PSI ! The lift works like new! :D :D
 

Replying to an old post like this makes for a disjointed mess in classic view.
Go to Classic view to see your post.
The majority of us here use classic and aren't going to bother clicking over to Modern to see your post in context. So you only get half the views - and half the help.
It's best to start an entirely NEW post if your old one is more than a couple of days old.
That way Everyone here will read it.
 
(quoted from post at 16:21:36 05/22/20)
Replying to an old post like this makes for a disjointed mess in classic view.
Go to Classic view to see your post.
The majority of us here use classic and aren't going to bother clicking over to Modern to see your post in context. So you only get half the views - and half the help.
It's best to start an entirely NEW post if your old one is more than a couple of days old.
That way Everyone here will read it.
aused me no problem! :D
 
I participate in several forums and they all resemble modern view, it seems to be a standard. Since classic view is so different, I find it too confusing to use. If I'm subscribed to a thread in modern view, there is no confusion at all. It's difficult to change from one to the other.
 

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