Hitatchi ex120 please help diagnose

[heyu29h]

We have a Hitatchi EX120 Grey Market ( there is no -# so i belive it to be a just a first run ex120, Serial # I2H-15076. Aprox 4000 hr's

So Far I have had no luck diagnosing, (13 years experiance in heavy equipment) Also had AIS Equpment send a tech. He is also baffeled. :Banghead

We purchase the machien and it worked good with decent power. Got it on its second job and the problems started.

1st. While traveling, I let go of the sticks and the right track kept going, I pushed the stick the other way and it continued in the same direction. I pulled up the control neutralizer valve, and the track kept turning. I shut the machien down. Thinking i had a broken spring on the main control valve spool. I disassembled the top of the main control valve. No broken spring, and no stuck spool. Reasembled and it fixed its self. Everything worked properly. Ever since I intermitantly have problems with the right track.

2nd. Using unit on our yard, everything working fine. All of the sudden, the unit started swinging to the right, and the left track started rotating. Thinking this was a pilot problem, I checked pilot pressure, right where it was suposed to be. Thinking it was posibly something in the shockless valve. I took the pilot lines off at the main control valve and capped the lines, and left the openings at the main valve open (so i wouldnt hydro-lock a spool in any direction) Started the unit and the track still turned and swing was still trying to swing. Shut the unit down and pulled top of main valve off again, again nothing visualy wrong, and no stuck spools. Reassembled, restarted unit, track still trying to turn and, unit still trying to swing. Played with controls for a while, and all the sudden everything went back to normal.

3rd. Used unit almost an entire day in yard everything working great! Shut the unit down to make a run. Came back restarted machien. All functions have almost no power.

Im baffeled if anyone has any insite on this problem please let me know.

Ps I have hydrolic schematics for this unit, in pdf format but they are too large to upload to this site. please let me know if you'd like to look at them and i'll email um to ya.
Note they denote a different model at the top but AIS assures me these are correct for this unit.

email is heyu29h@yahoo.com

Thanks in advance to anyone who can help!!!

 

[willie59]

You might try to send a PM to -3Doc, he's a Hitachi excavator mechanic. Here's a link to his profile page.

https://www.heavyequipmentforums.com/Forum/member.php?u=10926

 

[AtlasRob]

I have to assume there is a foriegn body in the hyd system.
Exactly what or where :Banghead

For a machine to work perfectly one second then start reacting wierd a few seconds later, has to have a foriegn body sticking spools IMHO.

 

[John C.]

I would agree that there is a floater somewhere in the system. Are any of the cylinders leaking down? Have you pulled filters and inspected for debris? Have you tried walking the machine up a steep hill? Travel motors do shot gun once in awhile creating the problems you describe.

Apparently you have been taking the top side of the valve apart and not the bottom. Perhaps the problem is in there. I suppose your machine has some kind of straight travel system. It's possible you could be getting a shorted flow from the other pump with a straight travel spool stuck.

You could put gauges on both pumps and see what is happening when the problems occur. Since you cut out the pilot circuit when you shut off the controls that would seem to eliminate the pilot system from being the problem.

It is apparent the machine is not safe to operate as it is. Don't give up on finding the problem.

 

[heyu29h]

What did you mean by travel motors shot gun sometimes?

Just wondered what you ment by travel motors shotguning?

thank.

 

[John C.]

Throwing out pieces of metal that jam up in other parts of the system.

 

[heyu29h]

ah thanks

had never heard that term, we always call it "taking a $h!t" lol

 

[CATD10N]

im thinking on that machine the computer needs to be reset and run a dig scan on the computer that will tell you the valve psi

 

[EddieWalker]

Sounds like what happened with my Case 1550 dozer. It worked great for awhile, but then one day, the left track didn't respond right away. Then it started doing the oposite of what I wanted it to do. Then it got to the point that it didn't work at all. It wasn't consistant, some days I'd work most of the day without a problem, but then it would act up on me. Usually it only happened once or twice, but within a few weeks, it got so bad that I had no control over it. Funny thing is that I was able to drive it back to my shop in reverse, but could not get it to go forward for nothing.

I did all the testing, research and asking around. It came down to my hydraulic pump that powers that side drive motor. I have thee pumps. One for the blade, and one for each drive motor. Case said that they would only sell me a new pump and not work on it. They wanted $25,000 for the pump, but I forget if that was the total job, or just the pump.

I looked around and found a place about an hour away that rebuilds them. It's a Sundstrand pump. Cost for the rebuild was $2,000 with me bringing the pump to them to work on and then me putting it back in again. They said that to gurantee the rebuild, they had to go through the drive motor too. That was another grand.

They told me that some seals were out, a spring was proken and that they had to fabricate a few parts that they could no longer get parts for it. The thoght the problem came from one of the metal parts in the pump that broke, and then went through the system.

I almost forgot, but one of the tests that I did was to pull the hydraulic filter for that pump and motor. Each pump has it's own filter. I cut it in half and found metal in the paper of the filter. That was the final proof that I needed to pull the pump.

I hope that's not your problem.

Eddie

 

[KenAl]

While I agree with the fact that if you pull up the neutralizer this cuts out the pilot system and therefore would suggest a stuck spool. I have twice now had something floating in a pilot line. Once a dirty hose was used to replace a blown hose and another time a Cat/Deere pattern selector valve seals had got into the pilot lines and would intermittantly stick the function. You have a perfect senerio in the fact that when it sticks it is stuck. Tee in a guage at valve bank pilot line and confirm the pilot pressure is not there when the function is stuck. You shut the machine and the spools are sentered?????? Now Not stuck????? That seems odd. Confirm the pilot pressure.

 

[heyu29h]

Thank you all for your help!

Thanks to anyone who helped give info on my problem.

It seems I left a very important bit of info out of my discription.

A friend stopped by and was helping me and when we put the unit under a load, it kinda growled a bit and kinda sounded like it swashed and unswashed the pumps a few times real fast.

As soon as my buddy heard it, he says to me "ut oh, thats the hitachi death chant" im like What? He says "your main pumps are coming appart".

Come to find out when the hitatchi pumps make that noise, its due to the metal coming off the plates inside the main pumps.

We took the main suction inlet off the pumps, and looking up in there you could see gouges in the ends of the barrels on both pumps.

We sent the pump to the rebuild shop today.

So thanks again for all your help and info! Good luck to you all in the future.

 

[Chris5500]

Even though you have diagnosed the problem, you still need to rectify it, not just by rebuilding or replacing the pump you need to perform a full system flush or your problem will still remain.

 

[AtlasRob]

Thanks to anyone who helped give info on my problem.
It seems I left a very important bit of info out of my discription.

Thank you very much for the feedback, personally I have never heard of the Hitachi death chant, rather like the xbox 360 light ring of death or whatever its called I suppose.

Very good info that will hopefully assist others. Just sorry that its such a bad scenario. :bash