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LD1 · Jan 9, 2023

New Holland 753-SERIES - BACKHOE(01/75 - 07/80) Parts

www.messicks.com

Look specifically at diagrams 006, 007 and 009 and 010

Quantumkev · Jan 16, 2023

Let me start by saying thanks to everyone that commented so far. You absolutely nailed it. Looks like it was for the “auto dig” feature. Odd that it was only on the boom control. I guess at some point it got removed from the bucket controls. The tractor is currently at the sellers location. I am trying to get the backhoe up off the ground so I can transport it back to my house.

The hose on the bucket is blown, and I was thinking that this odd linkage was what was causing the boom controls not to work, so I figured I could take the linkage off the bucket control and put it on the boom control as I can’t operate the bucket control due to blown hose, and I need to operate the boom control to move the tractor.

So here’s the thing. Even with the linkage removed from the bucket controls the bucket hose continues to spew hydraulic fluid…. I guess at this point I am looking for confirmation, but is it just that the seals in the valve body for the bucket controls are completely shot, and just allowing hydraulic fluid to pass? Is that what’s causing the hydraulic fluid to continue leaking from the blown hose even though the valve is in the neutral position?

If this is the case, is it even possible for me to pull the valve spool out with the valve body still mounted on the tractor? Or do I need to get the valve body on a bench before pulling the valve spool?

Any comments/suggestions gratefully accepted. Photo attached just because. Photos of tractors/tractor parts are fun!

LD1 · Jan 17, 2023

There are no seals in the valve body to "blow" that would cause that. The valve body is a metal spool in a metal bore....no seals just VERY tight tolerances.

The only seals are where the spools protrude out of the valve body where the linkage hooks and the return springs on the other end. These are just case seals that keep fluid IN the valve body.

So basically.....there is no rebuilding the valve.

So, did it start spewing fluid as soon as it was started? Or did it start leaking when you were moving the boom or dipper? Because even though the hose is blown....that bucket cylinder still holds quite a bit of oil. And moving other functions can allow the bucket to move via gravity. And without a sealed system and having a blow hose....hydraulics are not holding the bucket in place. Therefor gravity can move the bucket and expel fluid out of the cylinder.

If it isnt much trouble to get to....and since you need to do it anyway, go ahead and replace the hydraulic hose and proceed from there

Quantumkev · Jan 17, 2023

Thanks for the response, and please excuse my ignorance. I just assumed that there were o-rings sealing the spool positions, I didn’t realize that it was just really tight tolerances matching…. Makes for a whole lot simpler/reliable system though!!!

It does make me a little more confused though. I have the bucket strapped in a way that it shouldn’t be able to move.

When the tractor is static, and the engine is not running, I have no visible leakage, or at least if I do it is extremely slow.

As soon as I start the engine I start to see hydraulic fluid running out of the bottom of the boom. It’s not spraying, like it’s under great pressure, but it is running quickly enough that it is definitely being pumped. I am not moving the tractor, or operating any of the hydraulic control levers.

Bearing in mind what I mentioned above, that there is no operating linkage connected to the bucket valve, and your response, i guess the only Way that this can be happening is if the bucket valve is. Not properly centered? Even though it certainly appears that it is!

Am I missing something here? Or is there another explanation as to what I am seeing?

LD1 · Jan 17, 2023

Id just try replacing the hose before you do anything else.

I know on alot of mini-excavators.......due to their hydraulic systems, will continue to flow oil if a hose is removed even if you dont activate that function. Just simply having the engine running.

Now I dont think that should be happening on your machine.....but who knows just what is going on. And you need to replace the hose anyway, so just go ahead and do it and see if you cant get the thing working. OR at the very least, plug the leak and see if the other functions will operate

Quantumkev · Mar 5, 2023

So I finally managed to move the tractor back to my place, and start taking it apart to replace the blown hoses. It certainly seems like whatever that part was it was linked to the auto dig function. It is on the bucket cylinder. As I was taking all of the hoses off to get at the blown one, the bucket cylinder connections at the valves had these between the hose and the valve block. Anyone seen these before and know what they are? Are they some kind of flow restricter? And if so why are they only on the bucket cylinder?

Vigo327 · Mar 6, 2023

This is most likely a flow restrictor. It will probably have something like a disc with a hole in it (like a washer) and a spring against it so in one direction the washer seats and everything has to flow through the hole, but in the other direction the washer lifts and fluid can go ‘around’ it as well.

From what i know they are not typically on the bucket cylinder but usually on the boom and swing, boom to prevent you from ‘dropping’ it at full speed or swinging it too hard.

Tinhack · Mar 6, 2023

If it has auto dig, the bucket moves out with the boom moving in, doesn't it? To keep the bucket at the set level? That would explain the leak in the bucket line when you're trying to move the boom.

Egon · Mar 6, 2023

Quantumkev said:
So I finally managed to move the tractor back to my place, and start taking it apart to replace the blown hoses. It certainly seems like whatever that part was it was linked to the auto dig function. It is on the bucket cylinder. As I was taking all of the hoses off to get at the blown one, the bucket cylinder connections at the valves had these between the hose and the valve block. Anyone seen these before and know what they are? Are they some kind of flow restricter? And if so why are they only on the bucket cylinder?

Could that be a fitting to prevent erosion???