Komatsu PC50UU-2 slow hydraulics

[Gothgirl]

G'day all !
Does anyone have info on what could be causing my excavator's hydraulics to become extremely slow after 10 mins ? I have just completed a full hydro and filter change and cleaned the bottom one as its still in great condition.Someone on this forum mentioned the Banjo bolts can get clogged up and there is a heap of those !!!! Do I need to purge some air ??? My Bobcat didn't need this when I did a hydro and filter change. Thought they were all self air bleeding !!!
Thanx Guys and Girls.

 

[Scrapper]

So the machine worked fine before you replaced the hydraulic oil and filters?

 

[Gothgirl]

Komatsu PC series excavator

So the machine worked fine before you replaced the hydraulic oil and filters?

No, the hydraulics were starting to slow before hydro change, so went for the obvious thing and changed the oil and filters. Tracks, Turntable and Blade respond normally. Its all boom and bucket controls that are affected but only after 10 mins use, so cannot be a blockage or lack of engine revs.

 

[Tony]

No, the hydraulics were starting to slow before hydro change, so went for the obvious thing and changed the oil and filters. Tracks, Turntable and Blade respond normally. Its all boom and bucket controls that are affected but only after 10 mins use, so cannot be a blockage or lack of engine revs.

Goth,

Had a similar problem with a PC75UU-2 in our shop a few years ago. If my memory serves me correctly, the problem ended up being rooted in the hydraulic valve body that controls the "depth set" function (I assume your machine has the electronic function where you can set max depth and boom height?). We eliminated the valve "guts" so that it became merely a junction block, and the problem was solved. Of course, we did lose the functionality of the depth set, but the customer didn't use it anyway and thus saved a ton of diagnostic labor on the repair. The valve, if I recall, was located under the floorboard of the cab.

Good luck!
Tony

 

[Gothgirl]

Thanx Tony,
I had a look in my workshop manual about the depth and proximity settings and there is a switch to override this. Still doesn't explain how the machine all works fine for the first 10 mins, thereafter the boom, bucket curl slow to almost stop.
As its a heat related problem, could it be that there may be some air trapped in the boom and bucket cylinder ? Interesting how its only the r/h controller thats got the probs, the L/h controller, controls the arm and turntable and are all working fine, including grader blade and full power to the tracks. Gothgirl x

 

[Gothgirl]

Been looking at other threads on another forum in which other people have had the same problem, looks like it may be a spool valve problem. All they did was re-torque the spool valves and fixed the problem ! I will try this today and post my results. Only hope its this easy !!!!

 

[hmw]

Sorry for using such an old thread, but I am unable to write direct messages.

Did you ever fix your problem?

Thankss