Hydraulic Conundrum Long W/Photos

regularjay · Apr 22, 2012

Tractor in question is a well used B7200 with a gear (not hydro) transmission. 3 digit meter shows 650+ hours but who knows if or how many times it's rolled over. I've put less than 50 on it since my purchase. Right after I bought it I changed all the fluids and replaced the suction screen.

Since my purchase it has never seemed to have the oomph in the hydraulic system I feel it should. I replaced the 3-point cylinder O-ring (like a piston ring around the piston) and that helped the 3-point a lot (no longer drifts down). The 3-point still barely lifts a post hole digger and I cannot use it to dig any actual holes. Once the auger has pierced the surface (less than a foot) I cannot raise the digger at all. Over the weekend I had a landscape rake on the back. While clearing brush from the tines I discovered that with the position control in "lift" i.e. all the way up, I could manually push the rake down to the ground. To clarify - while its supposed to be lifting I can push it down. When I stop pushing down it would bring the rake back up but this doesn't seem proper. With the rake lifted and the lever released from full-up it will hold the rake even though I push down. It seems like fluid must be bypassing around somehow but I don't know how or where.

The pump feeds the loader control valve, the power beyond port from the loader valve feeds the 3-point. An overflow (or bypass or something) from the loader valve dumps into a port on top of the transmission. I also notice that if I remove the cap on the port I can see the flow of fluid from the loader control valve. When I actuate the loader to lift, lower, or curl, I see a flow of fluid from the loader control valve through the hose back to the port. When I "dump" the loader no fluid flows, Seems odd, It is power (not gravity) dump and fluid flows with the other three actions, seems like dumping ought to generate some flow as well. The loader has always seemd a bit weak as well. I have plumbed in a pressure guage and typically see 1000 - 1400 PSI where it ought to be closer to 1800 I believe. The pressure does seem to be lower after prolonged periods of work but its been less than 50 hours since fluid and filter were changed so I dont think it would be a filter clogging as fluid flows.

Overall view of Tractor with goofy single lever loader control and spiffy rearview mirror on loader support arm

"port" mentioned above where fluid from loader control valve returns to transmission/reseviour

Under the "thing" protruding next to the metal tag is a spring. It had a washer for a shim I added a couple more washers to try and up the pressure without much affect.

The "IN" port is capped off, the hose from the pump goes to the port in the center, (pointing up in 3rd picture) does this matter?

Not visible but just above the port where the pump is connected an allen head screw is threaded into the valve. Is this some sort of adjustment?

So, to summarize, Shoud I a pudgy middle aged regular guy with no super powers whatsoever be able to push an implement down that should be going up?

Does the fact that fluid returns to the transmission/resevior in only 3 of 4 possible operations of the loader control valve indicate something important?

Should my hydraulic pump be plumbed to the "IN" port of the loader control instead of the unmarked port it's plumbed to now? It seems to work this way it's just kinda weak.

What is the thing on the control valve I added shims to? Why didn't it help? Is there something else I can do that might help my situation?

Thank you in advance for any help or suggestions.

J_J · Apr 22, 2012

The thing you added shims to is the relief valve. Some are adjusted by an adjusting nut, and others by shims of varying thickness.

You could also have a worn pump, and probably needs a flow and pressure check.

Some valves have two IN ports, just use either one and plug the other.

On the 3pt, you appear to have some leakage in the 3pt cyl.

With the 3pt lever in neutral, can you move the 3pt arms. The 3pt lever in neutral should lock the arms in position.

Leakage from the 3pt could be several places, piston seals, relief valve, control valve spools, safety valve.

If you have a good 3pt system, any pressure should operate the lift arms. It would only be limited by the load and the pressure combination.

The tractor 3pt is rated for a certain load at a certain pressure.

A good manual and a 3000 psi pressure gage would help you in solving this problem .

Your fluid path should be something like this. Pump to FEL valve IN port, the fluid then exits out the FEL valve via a PB port or the return/tank port, then to 3pt, then tank.

Check out the flow path and see if things are connected correctly.

olde man · Apr 22, 2012

that looks like an old Dukes Fluid Power valve the side port your pump is going to looks like the optional inlet.the thing you put washers(remove those) in is the relief valve and you should have seen a response. the line running from your tank port to that fitting is your return for your functions flow. i would think there would be enough return flow from your tilts to notice on dump so i don't know if you have air trapped in there causing some freak response like that or maybe the amount of oil on the return side is so small it is only a trickle or both (just trying to come up with a feasible guess) at any rate it still functions. that screw could just be a plug for some cross port or something. it seems like an overall symptom; moderate pressure but not good movement under load which has me thinking about your pump, especially when you shimmed the rv with no results. does that tag on the valve have any legible info on it? i could possibly research it.

regularjay · Apr 23, 2012

It seems to be "plumbed" correctly. Just curious about use of the alternate "IN" port, it's not labeled wheras all the other ports are but, it does seem to work just kinda weak.

I do have a guage plumbed in - under no load I have no pressure under load from 3-point or loader I see 900 - 1400 PSI the pressure I see on the guage shows a bit less as things heat up with use (900 is the lowest I've seen)

With 3-point in neutral lift arms are stiff and I cannot move them.

olde man, what benefit will I see from removing the shims? I'm thinking I need more not less.

Because both loader & 3-point seem weak is it reasonable to assume my problem lies with the pump? Anything there I can shim, adjust or replace? I'm afraid of the cost of a new pump. If I had money I wouldn't have bought this poor abused Kubota in the 1st place.

I will attempt to get the info off the valve tag, thanks!

CJONE · Apr 23, 2012

Like Olde man I would lean towards the pump being weak. Like JJ said a pressure gage and a few min in the manual will solve it. But and a big BUT remove the shims you put in or with a new pump you may ruin it the first time you deadhead a cyl. The first thing most of my customers do is screw with the reliefs then when the actual problem is fixed it either blows a hose or the pump/drive system. CJ

J_J · Apr 23, 2012

regularjay,

Your pressure should be around 1400 to 1700 psi

If you are getting 1400 psi on the loader valve, then the 3pt relief is not set correctly, bad 3pt piston seals, perhaps worn spool on 3pt valve.

Your tractor is over 22 years old. Last year made 1990.

Does your tractor have a relief valve on the hyd block?

If so, then it may be set at 900 psi, and when you read the pressure on the gage in the FEL valve, then you are reading the 3pt relief. Try setting the 3pt relief to the same as the FEL relief.

You said you could not move the 3pt lift arms in neutral, the lift arms are supposed to be locked, and you should not be able to move them.

J_J · Apr 23, 2012

regularjay,

Here is your post from 2010, another forum.

B7200 w/1630 loader Hydraulic Question - OrangeTractorTalks - Everything Kubota

Have you had the same trouble since then?

regularjay · Apr 24, 2012

olde man Numbers on the valve are as follows;
2914 DWF
27FABS6M1AB

The guage I have does indeed indicate my pressure is lower than it should be. What I'm not sure of is if it's a worn pump or if pressure is leaking or bleeding off through the loader control valve somewhere it shouldn't.

I have been having this issue since my original post over at OTT. This machine is typically only used a few times a year for a day or two at a time. If I relied on it every day I would have spent more money in the first place.

I had no idea that the 3-point had it's own relief. Since I replaced the rubber piston ring some time ago it has workd O.K. (no longer leaks down under load) It lifts and carries a box blade, scraper blade and landscape rake without trouble. It is just to weak to lift my post hole digger out of a 10" deep hole thus rendering the PHD useless. I do have a service manual for this tractor but the pictures are basically impossible to see as they appear to be 5th generation photocopies copies of a lousy fax (Its in an OEM Kubota cover too)

I'm fervantly hoping I can shim, adjust, or repair my way to better performance. The price of a new pump scares me and I'm not sure a used one would be any better than what I have now.

Thanks all for you assistance.

J_J · Apr 24, 2012

Looking at Messicks hyd parts layout of your tractor, it appears that if you have the hyd block on the side of the tractor, and you have the FEL installed, then you have three relief valves on your tractor.

Fill in the data on the left for your tractor, and they will send you very good pictures of your parts and part numbers.

Kubota Parts for Tractors and Equipment