Kubota L35 big mistake on hydraulic loader valve looking for advice.

[PoTreeBoy]

That cant be right. Without a inlet relief on the loader valve people could/would fry the pump in everyday loader use.

Dan

The L35 is a plumber's nightmare. The fluid goes from the front pump back to the relief on the 3ph, then back up to the loader.

 

[TheOldHokie]

The L35 is a plumber's nightmare. The fluid goes from the front pump back to the relief on the 3ph, then back up to the loader.

I was pretty sure of that. Kubota did and still does use that routing on a lot of machines. I looked the L35 schematics over about a year ago and its an "interesting" design. Lots of levers to keep organized

Dan

 

[PoTreeBoy]

I assumex the blocked neutral just blew every thing on the bottom out. But if the bucket spool is shifted to "slow extend" the blocked tank core will see roghly 1.5 times inlet pressure so jaybe tgats what happened. What is tractor side relief set to and whats the rated max on the valve?

Dan

The relief is set at 2489 to 2560 psi and the valve is rated at 3000. I don't see a spec on the tank passage. I didn't think about the multiplication effect.

 

[TheOldHokie]

The relief is set at 2489 to 2560 psi and the valve is rated at 3000. I don't see a spec on the tank passage. I didn't think about the multiplication effect.

The tank port limit is going to be 500/600 PSI but thats not a burst pressure. The old grey iron in those valves is probably getting tired and this was a straw too much...

Dan

EDIT

 

[TheOldHokie]

The relief is set at 2489 to 2560 psi and the valve is rated at 3000. I don't see a spec on the tank passage. I didn't think about the multiplication effect.

BTW - you may not have considered the multiplication factor but you picked up on it immediatly. I also didnt think it completely through Since the boom is a serial circuit commanding lift at the same time as commanding dump multiplies pressure twice :

2500 PSI x 1.5 x 1.5 = 5625 PSJ

Youser!!

Dan

 

[Fluke216]

That cant be right. Without a inlet relief on the loader valve people could/would fry the pump in everyday loader use.

Dan

The L35 only hits a relief valve on that circuit if the BH is in place or the spool on the outlet is turned.
Yes it's a bad design in the way they made the relief at the end of the loop.
I believe it's done this way because that BH does not have a PB like newer valves, but I'm not sure.

OK, it looks like the tank passage (low pressure) is the one that blew out. @Fluke216, make sure the tank hose is connected correctly and not plugged. @TheOldHokie, do you see any other way this might be over pressured?

View attachment 162170

I went and got the Valve, the whole setup. Left before 2 got back after 10. I also got the pressure relief valve that was on that machine it looks better than mine. Should I have it tested or test it following the wsm. Thanks for all the information here much appreciated just wanted to clarify so I don’t screw something else up. The pressure relief valve didn’t work because I did not have the hoses connected? Additional info I had the boom raised and the bucket was fully dumped but wouldn’t roll back and I was obviously screwing with it more then I should have when it blew out.

 

[PoTreeBoy]

I went and got the Valve, the whole setup. Left before 2 got back after 10. I also got the pressure relief valve that was on that machine it looks better than mine. Should I have it tested or test it following the wsm. Thanks for all the information here much appreciated just wanted to clarify so I don’t screw something else up. The pressure relief valve didn’t work because I did not have the hoses connected? Additional info I had the boom raised and the bucket was fully dumped but wouldn’t roll back and I was obviously screwing with it more then I should have when it blew out.

Did that valve come off an L35, or a different model?

I don't know of a way to test the relief valve except on the tractor. You could put a gauge on the pump hose at the valve, start the tractor briefly, and see what pressure develops.

MOST IMPORTANT Make sure you don't have the tank and power beyond hoses reversed. The tank hose port is toward the tractor front and goes to a port on the transmission housing, I think. The power beyond hose comes off the back of the valve and goes to the backhoe.

The tank passage, where your valve broke out, is designed for low pressure, 500 psi max. You can see the casting is relatively thin there. Obviously, it can withstand more, but if the hose is blocked, it could see around 5000 psi with the relief valve operating correctly.

This could have happened even with the relief valve operating properly. And the backhoe hoses should be connected together when the backhoe is removed to prevent deadheading the pump against the relief. But I don't think that would have broken your valve. The only way I can see this happening is that the tank connection was plugged somehow.

 

[Fluke216]

Did that valve come off an L35, or a different model?

I don't know of a way to test the relief valve except on the tractor. You could put a gauge on the pump hose at the valve, start the tractor briefly, and see what pressure develops.

MOST IMPORTANT Make sure you don't have the tank and power beyond hoses reversed. The tank hose port is toward the tractor front and goes to a port on the transmission housing, I think. The power beyond hose comes off the back of the valve and goes to the backhoe.

The tank passage, where your valve broke out, is designed for low pressure, 500 psi max. You can see the casting is relatively thin there. Obviously, it can withstand more, but if the hose is blocked, it could see around 5000 psi with the relief valve operating correctly.

This could have happened even with the relief valve operating properly. And the backhoe hoses should be connected together when the backhoe is removed to prevent deadheading the pump against the relief. But I don't think that would have broken your valve. The only way I can see this happening is that the tank connection was plugged somehow.

yes the valve came off an L35. I’ll double checked that those weren’t reversed and they weren’t unless I made a mistake I thought they were different fitting like the PB has a strait fitting and hose had a 90 and the one to the rank had a 90 fitting and a strait on the hose. I’ll check that the hose one to the tank is not plugged somehow. I was doing more then I should have trying to roll the bucket back maybe it exerted a bunch of pressure quick somehow, or that’s how it seemed.

 

[Fluke216]

Did that valve come off an L35, or a different model?

I don't know of a way to test the relief valve except on the tractor. You could put a gauge on the pump hose at the valve, start the tractor briefly, and see what pressure develops.

MOST IMPORTANT Make sure you don't have the tank and power beyond hoses reversed. The tank hose port is toward the tractor front and goes to a port on the transmission housing, I think. The power beyond hose comes off the back of the valve and goes to the backhoe.

The tank passage, where your valve broke out, is designed for low pressure, 500 psi max. You can see the casting is relatively thin there. Obviously, it can withstand more, but if the hose is blocked, it could see around 5000 psi with the relief valve operating correctly.

This could have happened even with the relief valve operating properly. And the backhoe hoses should be connected together when the backhoe is removed to prevent deadheading the pump against the relief. But I don't think that would have broken your valve. The only way I can see this happening is that the tank connection was plugged somehow.

Does this make more sense if the tank and power beyond lines were reversed. Because I’m thinking that’s probably what happened the line from to the tank is clear.

 

[TheOldHokie]

Does this make more sense if the tank and power beyond lines were reversed. Because I’m thinking that’s probably what happened the line from to the tank is clear.

Swutching PB and tank does not create a deadhead. Blocking them does.

Dan

 

[Fluke216]

Swutching PB and tank does not create a deadhead. Blocking them does.

Dan

Hmmm I think they were definitely switched and the ones to the backhoe were not plugged together. Does that create the dead head?
I hooked the new one up double check led it was all hooked up correctly seems to function fine boom goes up and bucket dumps and curls. Only check that quick then shut it off.

 

[TheOldHokie]

Hmmm I think they were definitely switched and the ones to the backhoe were not plugged together. Does that create the dead head?
I hooked the new one up double check led it was all hooked up correctly seems to function fine boom goes up and bucket dumps and curls. Only check that quick then shut it off.

You have to understand things are inter-related

When the BH hoses are not looped together the PB circuit to the 3pt and from their back to tank is deadheaded. Thats the basic mistake and what happens as a result varies based on the upstream connections.

1. If PB and T are NOT REVERSED the PB port in the loader valve is deadheaded and over pressurized at all times but T is not. Dump and curl will work fine but lift and lower will not
2. If PB and T are REVERSED the PB port is NOT DEADHEADED . It simply dumps to tank and the 3pt will not work. The tank port IS DEADHEADED but it will only be over pressurized when you try to curl the bucket

Dan