Hi, I have a problem that the boom cylinders respond at expected speed when machine is cold, but after an hr or so and the oil temp comes up, it starts to move very slowly and sounds like the pressure relief valve is going off. All of a sudden (randomly) the sound will stop and the full response from the machine will come back, often sending the bucket crashing into the ground. None of the other functions seem to be effected. Thinking it might be a hydraulic spool that’s playing up but I’m not sure why it would be so much worse when machine is warm? Anyone else have suggestions on possible causes or solutions?
Sounds like your pilot controls. T- a gauge into the pilot lines controlling the effected function at the main control valve and watch what the pressure does when the problem occurs. If the pressure drops off then your joystick needs to be replaced or rebuilt.
Welcome to HEF Powerdig ! Maybe a sticking anti-drift valve?
Thanks for the replies! I think that mg2361 is on the right track. Now that I think about it, it only really effects the boom down function, not boom up. It certainly sounds like a closed check valve also. I’m going to pull it out to take a look at it. Any ideas why warm oil would cause it to play up more than when it’s cold? Thinking the lower viscosity of the warm oil is slipping past a bad seal/spool somewhere in the circuit that unloads the anti drift valve, so it can’t build enough pressure to open it. Anything in the attached diagram jump out as an obvious cause for such behavior?
I would check your pilot pressure first as Paul suggested in post #2.
If only boom down it’s your anti drift poppet. Common problem. Pull it out and leave it out.
will holding valve problem affect the boom down problem? i thought that it is the spool that will open up and release it to the return line?
Hey OP did you end up fixing this issue, I have an ex200 doing the exact same thing warm up slow boom down function, pilot pressure is fine, changed displacement valve solenoid, did it end up being the anti drift?