L**40 rear hydaulic pressure

kuboman · Dec 31, 2011

Looked high and low and can't find a spare port anywhere. Teeing into a steel line is a little above my pay grade.:laughing:

MHarryE · Dec 31, 2011

Darn, this thread is going on so long that I need to check my L5740 HSTC. The dealer said the remote flow and pressure is checked on all the machines they sell after installing the remotes and before customer delivery so I never questioned it. I have charts on different size simple reliefs and they all increase from cracking pressure to full flow, but surely Kubota would have selected a size that would have protected their 3,000 rated pump at full flow. Unfortunately my pressure gauges have 1/4 pipe and the QD couplers have 1/2 pipe and it is an 80 mile round trip to a store that sells hydraulic fittings or I would have numbers from mine at various engine speeds tomorrow. I will get numbers on mine as soon as I can.

J_J · Dec 31, 2011

There has to be a test port or they remove a steel line and use an adapter.

Kuboman,

Does your manual not tell you where to connect a test gage.

http://sz0011.wc.mail.comcast.net/s...167149.pdf?auth=co&loc=en_US&id=124920&part=2

How about putting the gage in a tee directly on the pump.

Does anyone know if there is an adapter for a banjo fitting that is used for a test rig.

The loader valve is fig H-280, and there should be a plug of fitting that can be used.

kuboman · Dec 31, 2011

MHarryE said:
Darn, this thread is going on so long that I need to check my L5740 HSTC. The dealer said the remote flow and pressure is checked on all the machines they sell after installing the remotes and before customer delivery so I never questioned it. I have charts on different size simple reliefs and they all increase from cracking pressure to full flow, but surely Kubota would have selected a size that would have protected their 3,000 rated pump at full flow. Unfortunately my pressure gauges have 1/4 pipe and the QD couplers have 1/2 pipe and it is an 80 mile round trip to a store that sells hydraulic fittings or I would have numbers from mine at various engine speeds tomorrow. I will get numbers on mine as soon as I can.

It is always good to check your own, but the official word from my dealer is that mine is working the way it is suppose to.:confused2: I do know the cabbed models have a different loader valve with somewhat different plumbing than mine even though the WSM does not differentiate. No one can explain the pressures I get other than to call it back pressure in the lines.:confused2: New one on me but until I experience a failure they are done with me. I still have

18 months left on warranty so I will run it and hope for the best.

Chilly807 · Dec 31, 2011

This is starting to sound like Kubota's stance on the jerky 3 point hitch on the L series compacts. "This is the way it's supposed to work"...

Since yours is significantly higher than both Paul (4shorts) and junkyarddog's, 2250 and 2500 psi respectively, I'd say there's definitely a problem with yours. I'd ask the dealer for something in writing stating that they found no problem, if they're unwilling to do that I'd contact the regional service rep and explain the issue. If a line blows and injures someone, you would have legal grounds that the dealer was aware of the problem while the machine was under warranty and did nothing on a safety-related issue.

One of these days I'll check my rear remote pressure, but since I have 3 relief valves in my system (main, loader, and remote valve reliefs), I'd be very surprised to see anything over the 2000 psi my Prince remote relief is set at. If it IS higher than 2000 psi, about the only reason is the line from the return to the sump could be undersized. If the valve and line are both rated to handle the full amount of hydraulic flow, there should be very little if any pressure rise once the relief opens.

Mine has really no relevance to this situation, I have a different tractor entirely with an aftermarket remote setup.

Be careful which cylinders/motors you use with your rear remotes, some of them (tie rod cylinders in particular) are only rated for 2500 psi. Although there's a safety factor built in, I still don't like knowingly exceeding the design limits.

If it were me, I'd run the tractor at full rpm and slowly check the pressure again. It may be much higher than 3200 psi if it's being caused by a restriction in the system as opposed to a valve being set incorrectly.

Pressure is caused by a restriction to flow, and you have much higher flow at full rpm than idle.

Sean

oldnslo · Dec 31, 2011

kuboman said:
Looked high and low and can't find a spare port anywhere. Teeing into a steel line is a little above my pay grade.:laughing:

Unfortunately and quite frequently their are no pressure taps on valves an yes teeing into a steel line without extra hose and fittings is a real challenge.

A possible solution to getting readings at both the FEL valve and the rear remote. I believe you have two gauges correct?

If yes and your valves allow you to "Feather' we (this means you Kubo

) can possibly simulate having a gauge in the pressure port.

Install the gauge like you have been in your loader circuit. If you have the second gauge and can see them both install it in the rear remote.

Now comes the fun part. Carefully feather the FEL control until you start to see pressure around 500 - 750 PSI would be good. Now while holding the FEL control in that exact position operate the rear valve. What pressure do you see in the FEL gauge? What pressure do you see in the Rear remote. If this a common circuit the pressures should be very similar.

Best of luck on this Kuboman since some valves allow feathering much better than others. If the loader control don't work possibly try the curl.

Roy

4shorts · Dec 31, 2011

kuboman · Dec 31, 2011

oldnslo said:
Unfortunately and quite frequently their are no pressure taps on valves an yes teeing into a steel line without extra hose and fittings is a real challenge.

A possible solution to getting readings at both the FEL valve and the rear remote. I believe you have two gauges correct?

If yes and your valves allow you to "Feather' we (this means you Kubo ) can possibly simulate having a gauge in the pressure port.

Install the gauge like you have been in your loader circuit. If you have the second gauge and can see them both install it in the rear remote.

Now comes the fun part. Carefully feather the FEL control until you start to see pressure around 500 - 750 PSI would be good. Now while holding the FEL control in that exact position operate the rear valve. What pressure do you see in the FEL gauge? What pressure do you see in the Rear remote. If this a common circuit the pressures should be very similar.

Best of luck on this Kuboman since some valves allow feathering much better than others. If the loader control don't work possibly try the curl.

Roy

Roy;

Well this just keeps getting more interesting. But this test you suggested I just did.
I installed a pressure gauge in the down circuit of the FEL deadhead.
I installed pressure gauge in rear remote, deadhead.
I feathered the down circuit to the loader and achieved a steady 700psi.
I then engaged the rear remote. I got 700 psi at the rear remote. Now here is the fun part. As I engaged the RR the loader lifted. Yep that is what I said. The loader went up. Disengaged the RR and the loader settled back down.:confused2:
Maybe someone who can read the schematics better than me can explain this.
This is making me a :drool::drool: idiot.

Chilly807 · Dec 31, 2011

kuboman said:
Roy;

Well this just keeps getting more interesting. But this test you suggested I just did.
I installed a pressure gauge in the down circuit of the FEL deadhead.
I installed pressure gauge in rear remote, deadhead.
I feathered the down circuit to the loader and achieved a steady 700psi.
I then engaged the rear remote. I got 700 psi at the rear remote. Now here is the fun part. As I engaged the RR the loader lifted. Yep that is what I said. The loader went up. Disengaged the RR and the loader settled back down.:confused2:
Maybe someone who can read the schematics better than me can explain this.
This is making me a :drool::drool: idiot.

If the rear remote circuit back-feeds pressure to the loader valve and the loader valve was leaking in the up direction, the larger surface on the piston side of the boom cylinders will create enough force to overcome the smaller piston surface on the rod side of the cylinders, meaning the loader will raise.

Feathering valves does funny things sometimes, I don't fully understand the valve geometry and the PB part of the circuit, I just know that it works, better in some cases than others obviously.

Did you happen to check the pressure at a higher engine speed, or still at idle?

Sean

oldnslo · Dec 31, 2011

kuboman said:
Roy;

Well this just keeps getting more interesting. But this test you suggested I just did.
I installed a pressure gauge in the down circuit of the FEL deadhead.
I installed pressure gauge in rear remote, deadhead.
I feathered the down circuit to the loader and achieved a steady 700psi.
I then engaged the rear remote. I got 700 psi at the rear remote. Now here is the fun part. As I engaged the RR the loader lifted. Yep that is what I said. The loader went up. Disengaged the RR and the loader settled back down.:confused2:
Maybe someone who can read the schematics better than me can explain this.
This is making me a :drool::drool: idiot.

Kubo,
Sorry, never even gave that a thought but yes the loader would lift some do to the spool configuration. What happened is that when you moving the loader valve to the lower position it also opens the cap end of the lift cylinders to the down stream PB which feeds the RR. Loader should only lift until both sides of the cylinders see pressure.

Did you get pressure readings or do the intelligent thing and go what the heck and stop?

This at least confirms again that the valves are plumbed correctly, but do to me not thinking it completely through caused you a little panic.

Would you be willing to try it again only possibly disconnect both lift hoses or use the curl. That spool does not feed flow down steam to the PB port. Would sure like to see if both pressures are the same with the RR dead headed.

If they are the same this will really scramble my pee brain.:confused2::confused2:

Sorry again

Roy