Hydraulics Issue - Hitachi Ex200 LC-5

This topic contains 7 replies and was last updated by dawson 8 years 2 months ago
Author
dawson
August 8th, 2013 9:03pm
Post
Hello, I own a hitachi Ex200 lc-5 and I am having an issue with the hydraulics. When the hydraulics warm up, the boom will not boom down slowly; it jerks at the start. Once it's engaged, it runs smoothly. The issue seems to only occur when starting to lower the boom. Can anyone help?
jim-owen
August 9th, 2013 3:18am
Two things came to mind:



1/ Air in the system. Have you cycled the boom up and down to evacuate the air? If there is air in the system, you will often have a burnt smell because of the diesel effect occurring in the system and the oil may start to darken or change colour.



2/ Have you added a different brand of oil. Sometimes the additives in the oils cause conflict and the additives drop out. If that's the case, you may have to change out the entire oil package. Alternatively, some sample people can tell if the additives are sufficient for your oil and your machine. It very well may be something as simple as lack of lubricity.



Hope this helps.
rodel-marata
August 30th, 2013 1:47am
look for internal leaking !!

electronexciter
October 27th, 2013 11:13am
As a Cat Tech I'm not familiar with the specifics of Hitachi hydraulics, however, I do know that there is very usually an antidrift valve for the boom up/down function. As the name suggests, the purpose of this valve is to prevent the boom from drifting down and the valve is only going to affect the boom down function. When you select boom down with your joystick, pilot or pump pressure must shift a poppet in a valve cartridge or shift a spool in the antidrift manifold block before oil will be sent to the hyd cylinder. Basically it is a load lock valve. If the valve is sticking, that could create your symptom. Sometimes these antidrift valves are a screw-in poppet valve cartridge and sometimes they are a separate manifold block that attaches to the hydraulic cylinder or in the cylinder lines near the cylinder, sometimes at the base of the boom. If it is the block manifold style, there might be a manual release screw on the manifold that you turn in to disable the lock valve just for testing purposes. Before doing this accurately measure the protrusion of the manual release screw so that you can restore it's original setting. I suggest trying to obtain a hydraulic schematic for your machine to see what exactly you have for antidrift in that circuit.



Since boom up is not affected, I think maybe we can conclude that it is unlikely that the main control valve spool is sticking. When you select your boom down function and the boom moves and then you release your joystick, does your boom stop moving right away?
ron-mellor
October 30th, 2013 7:20pm
Hello haven't posted in a long while. I would agree with electron exciter. Check the load holding valve and the pilot if has external pilot. In general terms the load holding valve is just a counterbalance. In load holding applications on cylinders it should be mounted on the cylinder or at the minimum mounted close by with hard line.. They work with the pressure source to open the return to tank in your application. Pressure acting to lower the boom activated opens the poppet on the load holding side allowing return to tank. The higher the pressure to open the valve the jerker the initial movement.
joseph-penman
December 30th, 2013 12:09am
It's a spool sticking in pilot signal manifold change whole valve. It is cheaper than ordering parts for it.
rodel-marata
December 30th, 2013 1:40am
yes your rigth Ron , its function as a counter balance or what we say automatic flow control,
ron-mellor
January 16th, 2014 7:29pm
Did you get the load holding straightend out?

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