Hi guys I am looking for some advice, my machine has a large decrease in hydraulic power one the oil get hot. once the machine is down in power oil pulse's from this housing down this pipe, it seams to be some sort of relief but I dont know for sure, I see in another thread a fellow with a similar problem, someone mentioned to him that the spring in the relief valve might have become weak and this becomes apparent once the oil is hot. If this may be the case where is it on my machine? also in the picture what is the part i have circled and what is it function? Many thanks Johnny
It's the pilot pump. Provides pilot pressure to your system.
Sorry to be silly but what is the purpose of of the pilot pressure? should there be pulses of oil going down it or a constant flow?
Multiple purposes. Your joysticks have pilot valves controlling the movements of the machine. Your travel pedals are connected to a pilot valve. There is a pilot line that shifts your travel motor from low speed to high speed...and a many other purposes.
Hi Johnny, Ye this is the pilot or servo system pump, seems you have a problem there, it shouldn't pulse, and if it isn't pumping properly the servo pressure will be low and then your main spool valves wont be operating fully resulting in apparent power loss, maybe check the pressure in the pilot system, might be that pump is duff.
check the pressure of the pilot pump. it should be at least 750 psi on 70 degree C hydraulic oil temp max. the temperature is critical. different hydraulic oil has different working temperature. the pulse is normal.
What is the right oil for this machine ?
Im not familiar with your brands there. Here we use hyplus 68 because our climate temp is 28-32 deg C.
On that style of main pump with High Speed Solenoids that are used to open and close numerous times per second to "hold" the swash at a certain angle. The high speed solenoids use pilot oil through the solenoids to achieve this. So pulsing is normal!!!! More frequent pulsing when hot, still normal due to increased leakage.
HI, i am having very similar problems with my Hitachi ex 120-3. i read another thread that a fellow was having this trouble with his 120-2 and he found that his displacement solenoid valve had a crack in the coil and it would allow oil to leak in when it got hot and slowly pressurize the coil causing a disconnect in the circuit. Does this sound possible and where is this valve on the 120-3?
I would say to check your case drain flow after the problem happens. If all the oil that the pump is trying to make goes out the case drain the pump is going bad. Email me at [email protected] for more info.