Constant high flow with zero pressure coming from hydraulic breaker/hammer lines

[Taat]

So short summary about this issue:
Without having the function engaged there is 100-110 litres per minute of oil coming through breaker lines about 50 litres on each side simultaneously, if I plug the lines with pressure gauges it shows zero pressure.

Machine is Takeuchi TB 1140, year 2006, 12.500 hours on it.
I have bought this used machine about three years ago and I already put some fixing into it. Hydraulic slew motor had to be completely rebuilt and recently I also completely rebuilt the main axial piston pumps (replaced all sliding metal parts and new seals with O-rings)…
Now my machine feels really strong, i use it to pull tree stumps and landscaping. Hoe attachment while pulling is strong enough to force drag the whole excavator to the stump if stumps don’t give way easily, in this case it seems that the weight of the machine is quite low for the pulling force of the hydraulic system.
But where I notice low power is on steep terrain with hydraulic motors (slew and travel). While all motors have pressure up to spec I still don’t know if enough flow gets to them and with flow meters being very expensive I decided to try and test the main pump flow through the breaker line and see if my rebuild was actually successful and breaker line flow would be up to spec.
As it turned out this test is impossible to perform because even though I drained the lines through the night as soon as I start the machine oil starts pouring from either left or right hose (I have breaker lines set to two way flow mode not one way breaker mode).
I used stopwatch and buckets, both hoses in one bucket, as soon as started the machine set to high engine rpm and calculated that oil from both lines pours at about 50-55 litres per minute in both buckets/hoses, resulting together in 100-110 litres per minute without having this auxiliary function engaged (might as well be tens to hundreds of hours since I even touched these auxiliary controls).
When i plugged the lines I measured pressure on these hoses and it is basically flowing with zero pressure.

Is there any way this could be normal behavior?
It doesn’t seem to be usable flow since it is not coming out pressurized, but still lots of oil and don’t believe there should be any coming out of these hoses if its function isn’t engaged…

 

[doobin]

I dont know about specifics to your case, but on a lot of machines I have found that the aux lines have a of flow without pressure when the engine is started and the quick couplers removed.

 

[Maxus]

Here's what the metal mind, chat GPT, thinks.....

Yes, it can be normal.
The important distinction is between flow and pressure. Hydraulic oil can move at a very high flow rate through an open line while producing virtually no pressure. Pressure only develops when the flow encounters resistance/load.
On a load-sensing/open-centre excavator hydraulic system, the auxiliary/breaker valve section can have neutral circulation, make-up/anti-cavitation flow, or gallery flow communicating with the auxiliary ports. With both hoses completely open into buckets, you're effectively giving that oil a near-zero-resistance route to atmosphere. Seeing substantial flow in that condition doesn't necessarily mean the auxiliary spool is being commanded.
The strongest evidence is what happens when you cap the hoses:
Open hoses → ~50–55 L/min from each
Capped hoses → ~0 bar
If those ports were actually receiving 100–110 L/min of commanded pump flow, capping them would cause pressure to rise very rapidly toward the relief setting. The fact that it doesn't strongly suggests you're measuring unloaded circulation rather than useful pump delivery.
There's another problem with using this as a main-pump test: adding the two bucket measurements together doesn't necessarily mean the pump is producing 100–110 L/min. Depending on the TB1140 valve arrangement, the oil appearing at the two auxiliary ports may come from different galleries/pump circuits or include oil being displaced/circulated through the valve block. You need the hydraulic schematic to establish exactly where it is coming from.
So I wouldn't use this bucket test to judge whether your rebuilt main pumps are producing their specified flow.
To test that properly, you need a hydraulic flow tester with a loading valve. You measure flow while progressively loading the circuit—for example, flow at low pressure, 100 bar, 200 bar, etc. A worn or incorrectly set pump can produce respectable free flow at essentially zero pressure but lose substantial flow as pressure rises.
That is particularly relevant to your symptoms: good cylinder force but weak/slow travel and slew on a gradient can coexist. Cylinder force mainly tells you the system can achieve pressure; it doesn't prove that the pumps are maintaining the required flow at pressure.
So, in short: yes, the zero-pressure flow from the open auxiliary hoses may be perfectly normal. The fact that the ports remain at essentially zero pressure when capped is the important clue. But the bucket test isn't a valid way of confirming the condition of the main pumps.

 

[JD450A]

Have you actually pressure and flow tested the pumps or are you assuming they are great ?

 

[doobin]

Have you actually pressure and flow tested the pumps or are you assuming they are great ?

From what I read he's trying to avoid buying gauges and flow testers.

This is one instance where getting a pro to test might save a lot of hassle. I remember his pump rebuild pics so I'd say he's pretty competent, just needs the right tools for this occasion.