1020 hydraulics haunted

[amattf]

I just got a '72 1020 w/ 37 loader that runs like a top; except for the hydraulics. It's my second 1020, so I've familiar w/ the closed center setup. Here's my issue. When I got it, it had been sitting outside unused for ~20 years. I drained the hydraulic fluid, cleaned the intake screen, changed the filter. Ran the tractor; no hydraulics for about 20 minutes. Then, after turning the steering wheel back and forth for about 10 minutes, the hydraulics came to life; bucket lifted, 3-point up, everything working.

Next day, I start it up, no hydraulics. I checked the main pump intake screen - Not there! Pulled out the stroke control valve, cleaned it, and put it back in. Hydraulics again! Ran for 10 minutes - gone again!

So, I got the missing screen for the pump, changed the fluid AGAIN just to be safe,
cleaned the filter relief valve and the transmission pump relief valve. Ran the tractor-no hydraulics. Put on a pressure gauge at the main pump. ~1000 psi, drops to 0 if I turn the steering wheel.

Tested the trans pump using the 100 gauge + bucket method as per the shop manual (twice). Always perfect!

Finally, I decided to rebuild the main 8 piston pump (already rebuilt one on my other 1020). Found an intake valve actually unscrewed part way; figured this must of been my culprit. Finished the rebuild, reassembled with a brand new stroke control valve. Again, no more than ~1300 PSI, goes to 0 when I do anything.

Finally, I just noticed that if I let it sit for about 10min, raise the rockshaft and _then_ start it, pressure shoots up to 2200+ PSI, rockshaft raises like normal. But, as soon as I do anything else (lower rockshaft, turn steering wheel, etc) I loose all hydraulics.

Could a bad power steering valve cause the main pump to never build pressure? The reservoir is always full, so I'm pretty sure the trans pump is fine. I'm out of ideas and really want to put that loader to use!

 

[JDemaris]

I assume you've got the little 1.3 c.i. eight cylinder German pump and not the bigger 2.4 c.i. eight cylinder USA pump? No screw-in inlet or outlet valves in the USA pump.

From what you describe, it sounds like the front pump is starving for oil.

Is the hydraulic-reserve tank in front always full ? (in front of the radiator). If it's working correctly, it keeps the front pump from running out of oil. If it's not full, pull the check valve out of the top and see what's going on.

If you had the big USA pump, there's a test-port in it for feed-oil, but the little German pump lacks that feature. If you could get a gauge hooked into the feed circuit, it would help to see what it reads when your hydraulics actually quit. Like I said, it's easy to do with the bigger pump. Any reading higher then zero is OK and indicates the main pump has oil available.

Also, I assume you've got the later closed-center power-steering and not the early 1020 with open-center? I know you said year 1972, but I can't recall how years correspond with design changes.

If you have the later closed-center steering valve, I can't think of any way it can stop feed oil from getting to the main pump. It CAN blow the big o-rings inside and rob a lot of pressure oil though.

What about a hydraulic reverser or hi-low? Do you have either? If so, either one of those CAN screw up feed to the main pump.

What about your PTO? Is it dry-clutch driven, transmission driven, or hydaulic-clutch driven? If the latter, that too can take away feed oil to the main pump.

Need more info. 1020 and 300 was available with many different options.

 

[amattf]

German pump, no reverser or hi-low, transmission driven pto (two stage clutch?), closed-center
steering, two remotes.

The front reserve tank is always full, I've checked it several times since it's been, like you said, acting oil starved. Might be able to put a gauge in the line from the reservoir, would that tell me anyting? I was able to get 1 gal in 10 secs at up 80psi when testing the trans pump.

 

[tim s]

Make up a hose to go from the big fitting on top of the pump, the one that goes up to the reservoir, leave that end unhooked, head the hose from the pump to a bucket and start it up,,see how much if any oil fills the bucket, you can time it to get an idea of flow, my bet is it will be weak or sluggish.. Tell us what you get, and we will go to the next step....

 

[Tx Jim]

If your SN is>45200-up then you have closed-center steering. Easy PS check is to remove and cap supply line that feeds PS. If you loader happens to have an ind control valve I wonder if it's the convertible type from open-closed(vice-versa) and has a blown quad-ring?

 

[rrlund]

That's a head banger for sure. Only similar problems I ever had with mine was after I had the pump rebuilt,it kept sending bits of ground up rubber into the destroker and I'd have to keep opening that to get the pieces out until the filter finally took care of it all.
The only other thing was when a spool went bad in the steering. Only way the loader would work was to turn the steering wheel all the way to the right and hold it tight against the stop.

 

[amattf]

Found one problem, my gauge hose had a small leak where I was attaching at the destroker plug, letting air in. Moved the gauge to the remote w/ a better hose, getting 2200 psi at start, 1500-1800 psi after she runs for more than a minute, 0-100 if I drop the rockshaft or turn the steering wheel.

Went ahead and checked the check valve on the input line, it was fine. Did the tranny pump test like Tim recommended. Really good flow all the time, no difference if pumps putting out rated pressure or 0 psi.

So, I guess I'm back to the main pump or the PS. Changed the stroke control when I rebuilt the pump, maybe a bad seat? Looked OK to me... Might try to scrounge up a cap for the PS tee.

 

[amattf]

Just capped the power steering; no change. What could I have missed on the rebuild? Replaced all o-rings, new thrust washers and quad ring, checked all the valves, etc. One inlet valve had a broken guide and was unscrewed, replaced that as well.

 

[Super 1020]

I usually never post but looks like you could use some help...

You've stated in two posts when you drop or lower the rockshaft you lose your system pressure. Lowering your rockshaft should have NO affect on system pressure as all it does is send trapped oil from rockshaft piston housing back to sump. Raising the rockshaft does as it needs oil to move the piston and fill cavity.

If you know for certain you are not starving the main hydraulic pump for oil, you have a bad internal leak somewhere. A very common failure is the rockshaft valve packings blown. Let the cold tractor warm up for a few minutes with rockshaft down and put your hand on the rockshaft housing and main case (internal passage) right next to where the lever goes in. It will most likely be warm right there due to oil flow. Raise rockshaft if still cold there, see if notice any difference depending where lever is. Oil is blowing by the packings in there and going straight to sump. Your post above states if raise rockshaft and start it you have 2200psi, lower it, lose pressure. You diagnosed the cause of problems but are chasing the affects.

Have worked on 100's of (and every model of) these "Dubuques" and never had one couldn't fix. Good luck and let us know what you find.

 

[Super 1020]

Forgot to add, if the rockshaft turns out not to be the culprit, check your two remote valves. The quickest way to eliminate them from the system is to cap of their high pressure line coming off down by the priority valve. Then you can see if there is any change in your hydraulics.

 

[Tx Jim]

Super 1020
I agree as I missed the statement of "loosing hyd psi" upon lowering 3pt.

I would remove hyd filler cap with engine running and look for spraying oil.

 

[amattf]

Ok, I disconnected the remotes and rockshaft right before the priority valve and replaced it with a gauge. System builds to 2300, drops to 0 if I demand oil (turn the steering wheel). Also, when there is no demand for oil, it seems to "hunt" for standby pressure, sometimes won't build up until I hit the wheel again. If I disconnect the steering as well, it will build to pressure, but hunt up and down a bit as well.

With good input from the tranny, all I can figure is:
- bad crankcase inlet valve
- bad stroke control seat (already replaced valve)
- worn piston bore/worn out pump

I'm about ready to pull the good pump off my other 1020 and drop it in, for sanity sake

 

[amattf]

Oh, and I meant crankcase _outlet_ valve.

 

[amattf]

So I bit the bullet and swapped pumps w/ my other "66 1020.

1 Power steering perfect
2 Rockshaft massively leaking by (lever won"t go down)
3 left remote working great, can tilt bucket just fine
4 right remote very weak (probably do to #2 above), can just barely lift loader

So, I"ve still got to figure out the pump for my other 1020; not as big a deal as it"s OC power steering, so I"m just missing my rockshaft. Looks like I need to rebuild the rockshaft on this guy, possibly the remotes. I"d really rather have an indepedent setup for the loader as well, plumbed back to the filter.

Thanks for the inputs guys. It was a little of everything adding up to a real headscratcher. Glad I had the luxury of changing out the pumps!

 

[Tx Jim]

Glad you're making progress.

Did you replace both of these stroke control valve parts in non-working pump? R72936 guide & AL71019 KIT

 

[amattf]

Conclusion: Finally got around to finishing this pump up. Ended up replacing the stroke control valve and seat like you suggested. Also replaced the piston springs and the outlet valve discs. These were cheap and I'll be replacing them anytime I open one of these pumps up from now on. Finally, I replaced the crankcase inlet valve pin and spring. Had to drive crankcase pin out from the high pressure side (PITA).

Installed on my '66 1020 and works perfectly. Thanks again guys.

Postmortem: For one thing, I overlooked the crankcase valve pin on the first rebuild, it seemed quite stuck. Also, the orifice between the crankcase and low pressure side seemed clogged upon closer inspection. Finally, the unscrewed inlet valve I found on the first build was a red herring and not the root cause of the problem.