kubota L235dt Hydraulic issue

[AKKAMAAN]

just about any time I am using the loader i have to rev the engine up high - usually pegging the foot peddle
thoughts ?

...duh....I repeat my self....valve could be over sized and wont build enough pressure at low rpm/flow....logic then, that you have to rev up engine rpm...


What rpm are you operating at????

Try to test operation with the lever moved to max end all the time, and see if you get a proportional cylinder speed increase to the rpm increase.....
lift FEL from ground to top (make sure cylinders are fully retracted, bucket over a ditch or of a "curb")

example
at 1000rpm full extend cycle= 10 sec's
at 2000rpm full extend cycle =5 sec's????
Tell me you cylinders dimensions, bore and stroke and we can calculate your work port flow.

 

[captjack]

I guess what I am trying to figure out is , what problems will I have if my loader valve is not plumbed the way Kubota says to plumb it. It kinda works the way it is.

There has to be a reason Kubota wants the pb port returning to the flange and the return going to the sump. Why ?

It was said on a previous post that it won't make a difference to have the PB returning to the flange.

This is what I am confused about. I ordered the PB plug and plan on installing things according to kubota manual. Then see if anything changes.

Is there any harm being done by having it installed the way I have it now ?

 

[J_J]

JJ

If I understand you right, you plumbed the input to the new valve from the pressure port of the flange, and the output of the PB, to the return on the flange, and the return from the new valve to the return line to tank.

this is not how it is plumbed - I only have 2 lines going to the loader valve. 1 from the flange to the valve and 1 returning to the flange(not from the PB)

We might be talking in circles here, but just because your old valve had a PB port, does not mean one has to use it, and if you chose not to use it, then you would route the return to the flange port to feed the 3pt. In that situation, the PB port would be plugged. So in this situation, you said you had to use both valves to get the FEL to operate better. When you use the 3pt, you are adding the 3pt cyl in the circuit, and when the cyl is fully extended, the pressure is realized through the complete hyd circuit. If in this circumstance, the FEL valve seems to work better, that means that the FEL valve is leaking, when only using the FEL valve.

If your old valve only had an input and a return port, then the pressure line goes to the FEL valve, and the return port is connected back to the flange port to feed the 3pt.

Using the new valve with PB installed, the pressure port on the flange goes to the FEL input, and the PB out goes back to the flange to feed the 3pt. The return port now, only dumps the fluid used by the FEL cylinders, and returns that unpressurized fluid back to the sump/reservoir.

Have you installed the new valve ? Have you set the relief valve pressure. If the circuit is testing out with the correct pressure, then using the FEL valve should give you all the pressure the pump can produce.

 

[J_J]

Quote:

There has to be a reason Kubota wants the pb port returning to the flange and the return going to the sump. Why ?


Because the input for the 3pt is coming from the FEL valve PB port to the in port on the flange port, and this is the route that the fluid will take to activate the 3pt. The return port off the FEL valve is unpressurized fluid, and should go to tank.

 

[mmurphy]

Quote:

There has to be a reason Kubota wants the pb port returning to the flange and the return going to the sump. Why ?


Because the input for the 3pt is coming from the FEL valve PB port to the in port on the flange port, and this is the route that the fluid will take to activate the 3pt. The return port off the FEL valve is unpressurized fluid, and should go to tank.

:thumbsup::thumbsup:Have to go with JJ.

 

[captjack]

Thank you for the reply.
If, I am supplying the three point with unpressurized flow , then I should have some 3pt performance issues correct ?

Would this cause heat build up or cavitation in the system ? If so then it would explain some of the issues I am having.

 

[kennyd]

Here is a WAG (wild **s guess):

The original valve worked, so a replacement valve should also, correct?

So, suppose the old valve was a CC (closed center) one and it was somehow parallel'ed into the system-and NOT in series as a valve should be. That could explain why the PB port was never used. So now we have added the proper OC (open center) valve with the existing plumbing in parallel...that could explain why there is "more power" to the 3PH when the new FEL valve is operated.

Again, this is a WAG, but if you have the old valve you could test it with air pressure by hooking it to the IN port and see if it flows freely to the OUT port while the spools are in neutral.

 

[J_J]

Thank you for the reply.
If, I am supplying the three point with unpressurized flow , then I should have some 3pt performance issues correct ?

Would this cause heat build up or cavitation in the system ? If so then it would explain some of the issues I am having.

If you are using the PB port, the fluid goes through it in the neutral position, and should go to the flange port and continue to the 3pt valve. If you only have a single outlet on the FEL valve, then all fluid flows through the FEL valve, including the cylinders expended fluid, and feeds the 3pt input line.

Using the new valve, use the PB port to supply the flange. The return port should only go to tank.

Backing up to the original statement. [ When I use the 3pt, and the FEL, I get better performance ]. This would be logical if the 3pt was really tight, and then if using the FEL, and you kept the 3pt in a relieved condition, the fluid would pressurize up to the relief valve setting of the 3pt, and if you kept it there while using the FEL, then the fluid would get hot.

 

[captjack]

I tossed the old 2 lever control valve out when I put this new valve on, so i have no way of testing it.

The pb port is not in use now - I just have the return line on the valve going to the 3pt.

Its one of those things were , if ya didnt know any better you wouldnt think anything was wrong. The loader works, the 3 pt works.

I noticed when I was using the pallet forks on the 3pt to pick up a tank of water. I had a rough idea of the weight because of the gallons of water I was picking up. When the 3 pt wouldnt budge it I realized something was wrong.
For the most part I am using a rake or a blade on the rear and it picks those up with no problem in the configuration its in now. Its only when im picking up heavy loads I notice how weak it is.

So I understand why now ! Thanks for clearing some of this up for me. I have to wait for the PB plug to get here and then get a hose made up to return fluid to the sump.

I will keep my fingers crossed that this clears up my problem.

 

[J_J]

After you install the PB sleeve, use a 3000 psi hyd gage and set the relief valve if you know what it should be. With the gage installed at the input to the FEL valve, extend the lift or curl cylinders, and check and or set the relief about 100 psi below the pump rated pressure. You can check the 3pt relief also by just raising the 3pt to max, and observing the pressure.