JD 301 hydraulics are dead!

[kennyd]

Also: the oil and filter was replaced three months ago with no visible signs of metal shavings; the oil level was never low; some, or all, of the metal shavings could be from grinding the gears when cold. After it warms up, the gears shift smoothly; and I didn't replace the oil after replacing the filter.

In addition to diagnosing the oil pressure with a gauge, I think I will disconnect the counterbalance connected to the 3-point hitch and see if that improves the lifting capabilities on the loader. If it does, then it would appear the pump is unable to pump at maximum pressure.

That is good info for sure...the metal is coming from somewhere then...

 

[AKKAMAAN]

I dont know specifically, I am only familiar with the newer CUT's, but most of the older JD's used CC systems...

I have seen that mixed brass steel scrap coming out of swash plate pumps (thru case drain to tank, case drain is usually plumbed to by pass return filter), where the swash plate bearings(if brass) start break down....pump can still deliver occationly till it bearings are totally out....."Bigger" pumps use ball bearings though...

 

[kenstrac]

I'm new here trying to get some advice on repairing my tractor.

The tractor is a 1973 John Deere 301 with a front loader and a rear 3-point hitch. After working the tractor for several hours my hydraulic system stopped working (both the loader and 3-point hitch would not work) but the tractor would continue to drive forward and back with the power steering working sporadically. Initially, I thought an internal relief valve opened up and pressure was getting bled off internally, particularly since there was no external leaks or strange noises coming from the tractor or pump. I stopped the tractor, turned it off, and let it sit for about 15 minutes. I then started it and moved it forward, and in the process of doing so, the hydraulics came back to life again like there was no problem. Well the next weekend the hydraulics started to act up again and this time started to simply loose pressure (i.e. loader would slowly raise until it wouldn't raise at all). Again, both the loader and the 3-point hitch were affected, but the tractor could still be moved.

In attempting to diagnose the problem, I first disconnected the coupler on the hydraulic pump to disconnect it from the crank off the front of the motor and move the pump by hand. To my surprise, I was able to move the pump input shaft by hand (I thought it would be much more difficult, but dismissed it since it wasn't under pressure). Next I dropped the filter bowl to replace the filter element under the tractor, and ......crap......the oil on the outside of the filter was contaminated with what appears to be brass and metal shavings. I replaced the filter anyway, fired up the tractor and drove it around for about 10 minutes. Upon the initial startup I had hydraulic pressure, or at least enough to raise the loader and the 3-point hitch with about 1500 pounds hanging off of it. However, after about 5 minutes of operation, the loader started to act sluggish until is wouldn't raise at all. Same with the 3-point hitch.

Because I found metallic material in the oil, I'm thinking the hydraulic pump died. But if the pump was dead, how could it build enough pressure to raise the loader? Also, where would the metallic material be coming from? I suspect the pump, but could it also be coming from the wet clutch on the reverser?

Any advice on diagnosing my problem and repairing it would be much appreciated.

Thanks in advance, Don.

You have two pumps an OC pump in the belly and a CC on the front it sounds like the OC pump is not putting out enough or you have crap in the priority valve.
change the filter again ,remove the priority divert er valve on the left side of the tractor located between your left foot and rear axle make sure everything is clean before during and after.
Disassemble valve you will find a passage with a piston and spring remove and clean I remove the spring and put piston back in bore and see if it moves freely back and forth run some 800 grit crocus cloth around piston and in bore lightly, clean up and blow out with air reassemble spring and piston as you found them install on tractor and try.
NOTE do not run tractor for long if the loader is not working this will ruin your front pump.

 

[jeep67]

Well it looks like I will have my work cut out for me. I will take a look at the priority valve and post my finding here. Thanks for the feedback.

 

[true temper]

Kenstrac has it right. To check pump pressure on the front of the pump there is a square valve block held on with 4 bolts. There is two plugs one on top of the other on the side of the block, the top plug is hydralic stand by pressure. the bottom plug is charge pressure. If the pump is original the plugs take a 1/2" wrench and is a #4 o ring boss fitting. If the pump has been replaced it will have a metal serial # tag on it, the plugs will take a 3/4" wrench to get the plugs out and you will need a metric oring boss fittting to check the pressure.

 

[jeep67]

Does it make a difference that from time to time, particularly just after startup, the hydraulic system would chatter as if an internal valve would open and close rapidly? Often it would only occur for a few seconds before stopping, and it would seldomly occur when it was hot. Also, cycling the loader up and down would seem to help.

 

[kenstrac]

Does it make a difference that from time to time, particularly just after startup, the hydraulic system would chatter as if an internal valve would open and close rapidly? Often it would only occur for a few seconds before stopping, and it would seldomly occur when it was hot. Also, cycling the loader up and down would seem to help.

This is how the system works.
The oc pump draws oil from the filter up a large tube to pump that is located high up in the transmission case (not submersed in oil) the oil then dist.to the PS brake and accumulator and CC pump if you loose flow in the system the priority valve will direct the oil to power steering and brakes (last thing you want to go). At this point the CC pump is not getting any oil.
Cause of loss on OC side.
#1pickup plugged
#2 filter plugged or restricted
#3pickup tube O-ring bad pickup tube attachment tab has a crack
#4bad pump
#5 bad PS unit allowing to much oil to bypass
#6 bad brake control (if ok till brakes applied then brake cyl
#7diverter valve spring or piston hanging in bore
CC pump operation The oil is forced into the CC pump inlet by the OC pump the pump brings the oil pressure up to 2500 PsI and holds it there with no flow until a valve is open then it starts pumping the volume that is required out the outlet of the pump. the third smaller line moves the oil through the oil cooler to cool the pump in long destroked periods.
Cause of loss on CC side
#1 no oil to pump see above
#2 bad pump dirt in pump not allowing pump to stroke
#3 destroked cold weather aid manual valve open, small valve that looks like petcock on pump. auto type solenoid on pump dirt under seat plunger hung up solenoid should only energize when the starter is engaged.
Since my experience has only been with backhoes and never had to trouble shoot tractors with 3PTH thats as far as I can go.
The metal in the oil that you mentioned in your first post could be your wet brake lining from normal wear or a pieces that have separated.
The first thing that I would do is remove anything you have on the TPH just in case you loose hyd.to check what hyd system that the TPH is hooked to if the bucket dosn't work and you have PS and brakes and it lifts it's probably hooked into the OC system.
I would concentrate my effort on the filter area make sure there is no ice in the system and the priority valve they are the easiest.
If you have to get into the system any further I suggest you purchase a manual.

 

[jeep67]

Thanks for describing the way in which this tractor's hydraulic system works....it is a huge help! I plan on taking a stab at looking over the tractor this Friday. I'll post up photos etc. along with any additional questions I have. Thanks.

 

[J_J]

That chatter sound you hear, could be pump cavitation, and if allowed long enough, could cause damage. Perhaps the fluid for your tractor is not matched for your temperature. Input filter clogged.

 

[kenstrac]

If you need any further INFO get me over here.
http://******************.com/search.php?searchid=70574

There seems to be a bad echo on the hydraulics forum here!