Hitachi ex120-3 cavitation/aeration

[qwertylad]

Hello all, looking for some help diagnosing my old beater.

In the past few hours of use, the machine will whine like it's out of fluid under heavy load, particularly when swinging, but eventually with any function. Power is about 1/2 what it was before issue. The hydro tank is very bubbly after use, but settles down after a few hours sitting.

I've since replaced the pilot, suction, and return filters on the hydraulic system. No improvement. Maybe a little worse.

I also totally drained the hydro tank and refilled with new aw46.

Then today, I drained again, and checked the piping from the reservoir to make sure it was clear. I then ran the machine without the suction filter, which made no difference.

Is my pump done or should I look somewhere else for vacuum? Maybe somewhere air is mixing in, causing aeration?

 

[qwertylad]

Hello all, looking for some help diagnosing my old beater.

In the past few hours of use, the machine will whine like it's out of fluid under heavy load, particularly when swinging, but eventually with any function. Power is about 1/2 what it was before issue. The hydro tank is very bubbly after use, but settles down after a few hours sitting.

I've since replaced the pilot, suction, and return filters on the hydraulic system. No improvement. Maybe a little worse.

I also totally drained the hydro tank and refilled with new aw46.

Then today, I drained again, and checked the piping from the reservoir to make sure it was clear. I then ran the machine without the suction filter, which made no difference.

Is my pump done or should I look somewhere else for vacuum? Maybe somewhere air is mixing in, causing aeration?

Some extra info:
Machine is a grey market
97, I believe
8k hours
Engine runs great, no stalling or bogging.

I've just started running the machine again after sitting for the winter. Had to clean the fuel tank out to get it going properly.

 

[Zewnten]

Some old timers put foaming shaving cream around suction lines and look for where it sucks in. Personally I just feel how hard the suction hoses are and if they're over 8 years old they're probably do for replacement.

 

[qwertylad]

Some old timers put foaming shaving cream around suction lines and look for where it sucks in. Personally I just feel how hard the suction hoses are and if they're over 8 years old they're probably do for replacement.

I have my doubts that it's actually pulling air in before the pump. There's a lot of pressure built up in the reservoir after use, which I would expect to force fluid out of any leaks in that big pipe.

However, don't know where else air would be entering the system. Other suction lines? Do those exist?

 

[Zewnten]

Up to you but unless its sucking air in through a cylinder when you retract that is where I would start.

 

[qwertylad]

I see there's a "make up valve" that lets fluid flow into the swing device when it's turning on inertia. The manual says this is to prevent cavitation at the pump. Maybe I'll pull the line and valve to make sure they're clear.

 

[HitachiGuy]

Did you bleed the pump after you drained the oil ?can take out a pump very fast if you didn’t. Have you plumbed any attachments on lately ? Don’t run with out the suction screen ! The pumps suck so hard they create a vortex and will cavitate with out it in place .Was it in place ?

 

[qwertylad]

Wow, didn't think of that. I just took the screen out for a test run, but it's been in the machine otherwise.

No new attachments, just an old hydro thumb.

I didn't bleed the pump the first time. After a while I did take that Allen bolt out of the top of the pump at idle. The fluid coming out looked ok. No air pockets.

Thanks for the tips Hitachi guy. Do you think anything that's not a pump could cause cavitation at this point?

 

[HitachiGuy]

Cycle time each track . Lift one side up mark a pad . Once it’s rotating measure with a stop watch 3 complete revolutions. Then do the other side . Compare times. There are specs for cycle times for each function . This will tell you what kind of shape the pumps are in if the times are way out of spec

 

[qwertylad]

Cycle time each track . Lift one side up mark a pad . Once it’s rotating measure with a stop watch 3 complete revolutions. Then do the other side . Compare times. There are specs for cycle times for each function . This will tell you what kind of shape the pumps are in if the times are way out of spec

I did this a while ago, and it was about 1/2 the speed it should be. The pump still can't push as hard if the oil is too aerated, though. So can you really say it's the pump's fault just by its output?

On another note, the problem is not nearly as bad since flushing the system of the old cheapo fluid and replacing with hygard. It's not 100% better, but substantial.

 

[Diesel Dave]

Before the first start of the machine for the day,remove the hydraulic tank lid.
Start the machine and at about half throttle look at the oil coming into the tank from the filter housing. Back in the day on a Deere “E” model we had a cracked tube from the filter housing outlet spraying oil in different directions into the tank. The aerated oil was chewing up the main pumps concave valve plates very quick. Not common obviously but something to check.

 

[qwertylad]

Before the first start of the machine for the day,remove the hydraulic tank lid.
Start the machine and at about half throttle look at the oil coming into the tank from the filter housing. Back in the day on a Deere “E” model we had a cracked tube from the filter housing outlet spraying oil in different directions into the tank. The aerated oil was chewing up the main pumps concave valve plates very quick. Not common obviously but something to check.

Ok, interesting idea. I've also been meaning to look at the fluid flowing to see if it comes out differently depending on the function. Will have to do that tomorrow.
Thanks

 

[qwertylad]

Just putting this to rest:
I pulled the pump off and the valve block was worn down on one side. Now I just have to work out my fuel starvation issue and I'll be back to digging.