Hitachi EX450 LC-5 hydraulics problem

[CJLennon]

Hey Folks, I thought I would run this by you to see if you have any magic. I have a Hitachi EX450 LC-5 excavator. The first 5-15 minutes, everything is OK. After 5 minutes, the outside pump that runs the aux, the left side drive and the other stuff backs down to where the left side travel is about 25% of the right side. Doing some initial problem determination work, I found the following:

1.) It appears that the outside pump is failing. It appears that it is falling back into a partial pressure/flow mode of operation because it does pump but just not much.

2.) Using the DR EX scan tool, no error codes are posted so we feel it is not electrical.

3.) It appears the swashplate on the outside (failing) pump is locked into a fixed position to give a limited pressure/flow because the voltage signal coming out of the swashplate sensor does not change from unloaded to loaded, when the failure condition occurs.

4.) Same thing with the voltage coming out of the pressure sensor on the outside (failing) pump - there is no change regardless of load placed on the pump.

5.) I have swapped the pressure switch harness (moved the outside pump pressure sensor harness to the inside pump pressure sensor and the inside pump harness to the outside pump) and it made no difference.

6.) I have swapped the solenoid harnesses (inside one with the outside one) and this also made no difference.

Because of the things I documented above, I feel that it is not an electrical problem nor is it a sensor/solenoid problem. An uneducated guess says that it is probably a mechanical problem in the pump itself. Now, for the big question! What type of mechanical failure would occur in one of these pumps when the pump is warmed up (5-15 minutes of running) but does not occur when it is cold? This all of a sudden one day started happening. There were no changes to the system nor was it worked on by any of our mechanics. Also, if you made it to the bottom of this post and got any of this, you are good! And, thank you for your efforts. So, any one out there that thinks they got this one figured out? If you do, I;ll make sure you become famous. Thank you very much to all of you that got through this post! :notworthy

 

[cps]

Hi CJ
First of do you know if there is a differnce in flow of the two pumps, im not sure if the DR EX tool can do this, a flow meter would be the best way to go! Also im guessing that all functions from the outside pump are slowing, not just the drive! If this is the case you can rule out the centre joint(if you hav'nt already)!

A flow test would tell you more, and if you think you have ruled out all else it could well be the pump!

Just thinking out here, it could have and interal crack if it happens when it gets hot!

Hope this helps abit!

CPS:drinkup

 

[superwrench0166]

ok been a while we got rid of ours. a sensor i think you must check and adjust theese with the dr ex. you put the pumps in full stroke and check make sure its adjusted properly. also you should check to make sure that the computer is sending the stroke signal to the pump usually a led diode in the plug that controls the pump swashplate angle. same problem your having is why we got rid of ours. we tried pump rebuild new harness i dont know how many new computers always was another sensor going bad. two sensors on the main valve body have a very big part of the play. without having the manual its hard to remember. your lucky you have a dr ex

 

[g-man]

I've been in this situation before on one of ours. We had a hairline crack inside the case. We could not figure out what was going on at first. Everything worked good for the first few minutes then it all went haywire. Rebuilding the pump will not fix the problem you have to replace it with another one. We tried rebuilding ours about four times even sent it to the manufacture. NO GOOD!!!! We put a new one on fixed the problem.

 

[CJLennon]

Thanks!

Thank you to all that responded. Just an update. We show that the front pump is putting out a low/limited amount of pressure. It will drive the left track but very slowly - about 25% speed compared to the right track so we end up doing a lot of circles. The crack theory is a good one. Didn't think of that - thanks!!!! I'll keep you folks posted on what we may find. Thanks again to all and to any one else that has any ideas.

Chris