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…
Just maybe there's some failed 0 rings in the control bank that are causing this and given the hours your machine has done becomes a big possibility. Flow = speed, pressure = power. Therefore the weakness in the travel drive is most likely pressure related and the thing they have in common is the control bank. Pressure testing as many functions as possible will help find what is at fault. A way of checking the track drive and slew speeds is to lift the track off the ground, mark a spot on the track then run it flatout and time it, same for the slew. This gives you flow but not pressure.
That hydraulic circuit, and likely all of them, have anit-cavitation valves for A and B ports at the control valves. The anti-cavitation valves allow oil to flow into lines to prevent a vacuum which would cause cavitation if you were to overcome a relief valve and move a cylinder or motor. That movement would cause a vacuum on the back side of the actuator. Anti-cavitation valves come from tank return lines, which are under a small amount of "return" pressure when engine is running, that's why you have flow when you start it with lines disconnected.
So this symptom can be considered as normal? I know anti cavitation valves are mounted on hydraulic motors because inertia is a lot bigger on them. I also don’t see any marked on my hydraulic schematic, following the lines it only gets back to the closed spool or to the port reliefs. I will try to back follow them on the machine to see.
I was thinking in this direction, either seals or damaged section in control valve.
It would be unusual for more than 1 control valve to be damaged but not impossible. A tractor I owned had 6 hydraulic couplings and not one of them had the same pressure and all were 1000psi or more below what the pump was producing. Fitted new 0 rings, problem fixed. Pressure tested every thing and found the problem, retested after the repair to confirm the fix and went back to work a happy chappy.
Flow of oil on an open connection is normal. This is why I carry steel fitting plugs and caps. Just had an EC160B fail an arm cylinder hose. As soon as machine was started, oil gushed out. Totally normal.
Okay, thank you. So basically there is no need to look into this… 100l/26gl per minute seemed like a lot of oil just flowing from somewhere.
Yes, it would be normal if that control valve have anti cavitation valves on the ports. Which most excavators do because of the work they do. Imagine you're digging a trench and come upon an imbedded rock. You get the bucket teeth under it, bucket won't roll it so you try boom up. In the process of boom up it pops the bucket relief valve and rolls the bucket. That relief valve would exhaust of from the piston side of the bucket cylinder, but the rod side is blocked, instant cavitation, which is deadly to hydraulic components, that's why excavators typically have anti cavitation valves on control valve ports.