Hydraullic Strain

Kubota-monkey · May 8, 2000

Yesterday I moved the biggest rock with my L35. There was no way to fit it in the bucket but it stuck so it was perfectly balanced. The thing had to weigh over 2000 lbs and the loader is only designed to pick up 1500. At first I couldnt lift it on low rpm but i boosted it all the way and i could lift the rock verrry slowly. This is definelty not something I do on a regular basis but I needed the rock out of my way. Does anyone know what will happen if the hydraullics are pushed to the limit? Any info appreciated!

M. Sullivan · May 8, 2000

Pop goes the weakest link in the hydraulic system. If you're lucky (including not injured), just a hose to coupling connection. Gets worse from there--coupling seals, block seals, pump seals.....

Don't know about your model, but the fact it would barely move at WOT says too much. Safer to try and roll or drag it out of the way, then worst case hire a big machine (cheaper than the repair bill--and the other damage done that did not result in failure, yet). Learned my lesson pushing small garden tractors too far/hard with a f. blades.

MChalkley · May 8, 2000

I can tell you the answer to that one - I do it all the time! /w3tcompact/icons/smile.gif

What happens is that the relief valve designed to prevent you from damaging anything opens and the pressure is vented back to tank. This actually occurs every time you extend or retract a cylinder to its limit of travel, so it's not like you'd notice it.

This isn't to say that you can't break something else, of course, but your Kubota was designed to handle all the pressure the relief valve will allow the pump to generate. So, you don't need to worry about damaging it that way.

Mark

M. Sullivan · May 9, 2000

Stand corrected. Does the 2710 have the same protection?? My dealer said DO NOT overload, or will get expensive, and possibly dangerous. Manual does not reference an over-P valve or protection either.......

_RaT_ · May 9, 2000

Hydraulic pressure is bypassed in virtually all hydraulic systems on tractors including your power steering pump, equipment pump and the pump that runs your diesel engine with some obvious exceptions like hydraulic brakes, it has to be. The fluid is pressurerized by the hydraulic pump and, if no fluid is used, it is simply "bypassed" by the unloader which has a preset pressure at which it "pops" or releases the necessary fluid to maintain the preset pressure. That is why you always have hydraulic fluid available to run your loader etc. immediately. If you have ever used a pressure washer, the same principal applies, the pump doesn't continue building up the pressure, it simply brings it to the preset unlaoder pressure and if none or only a small amount is used, it returns via the unloader to be pumped again. Its not the hydraulics that I worry about its the physical stress's you put on the loader, frame etc.. But that is something that you observe while doing the work. I am sure I have moved rocks in excess of 5000lb or more with a 2000 lb loader, I just skid it, if the tractor can't move it, its the tires that let me know. When you move heavy items, just do it sloooow.

Bird · May 9, 2000

I sure don't like to do it, and I don't hold the lever back very long if the bucket won't raise, but gosh, I've tried many times to pick up something that was too big, especially trying to pull up little trees and big fence posts set in concrete. And I've pulled many posts by chaining them to the bucket, lifting all it could, then rocking it back and forth with the hydro pedals until they started up.

Bird

PaulB · May 9, 2000

Is the relief valve opening and shunting hydraulic fluid what creates the whining noise I hear coming from the loader when I try to lift something too big? Same noise I hear when i turn the wheels all the way to one side and leave them there too long - manual actually says not to do this too often or you can hurt the hydraulics.

gordon · May 9, 2000

Very good detail yet very understandable using the pressure washer good post.
What happens when the unloader doesn't kick as fast as the lever is hit and the pistons get a good jolt before the bypass kicks in-----opps I think I just blew a seal----this can happen. But overloading the loader I'm sorry to say I do it all the time but it's not a good habit to get into, to bad I've already got the bad habit. Seems like no matter how strong a machine I've got I always need just alittle more. Never happy I guess.
Not so much on a new machine but once you get a good amount of hours on it parts start to wear and fun things start to happen.
Thought I blew a line the other day in my cab on my back, I was wrong just spilled my coffee---opps---/w3tcompact/icons/smile.gif did scare the heck out of me for a second though until I figured out what happened.
Gordon

MChalkley · May 9, 2000

PaulB - Yep, that's the noise. And it's not that it really hurts the system per se'. The problem is that the oil squeezing past the relief valve gets very hot. Dino oil can get hot enough to actually get ruined. Synthetics will handle the higher temps, but it's not a good idea to leave the system in the 'relief valve popped' position long because all that heat is being transferred to everything else.

M. Sullivan - your dealer is over-simplifying. Ask him why something doesn't pop if you don't release the lever instantly when your bucket goes to full dump... He'll figure it out. Now if he was saying that you shouldn't hold the lever in a positon causing the relief valve to 'pop' for an extended period of time, whether it be by trying to pick up something too heavy, or by holding it after the cylinders have fully retracted or extended, he should just say so. But tell him not to over-simplify. It gives people the wrong idea. /w3tcompact/icons/smile.gif

Bird - what you described is exactly the way it's supposed to work, right? I mean, if it won't do it immediately, work with it a little. Like you say, I don't just hold it forever if nothing's budging, but you try this, then you try that, and eventually you get it going, or not, but nothing breaks - it was meant to be used that way.

Mark

richh · May 9, 2000

I have a 350 case on tracks with a bucket and I have killed the engine trying to dig up trees. This is just using the hyd. and or putting power to the ground vi the tracks. THIS MACH. HAS A 900 LB COUNTER WT. on the back on 2 arms that stick out the back about a foot and you can put it right on its nose if you can get a good enough bite on a stump. It works well but there days I wish I had a 450 so I would'nt have to push it so hard. But IM allways impresed by hydraullics!!!!!!!!!!!!!!!
Rich