Hitachi EX-120-1 repairs

[danc]

Hi all

I have a Hitachi ex-120-1, this is my 1st excavator and I use it for works around my own property.
I don’t have an operators manual, so real greenhorn, so bear with me if questions seem silly.!!.

I am building a house at the movement so with little spare time I try and squeeze in some repairs to the 120. I have only spent a few hundred hours in this machine, and the problem with the track motors, is there since I bought it, and got no worse.


When I lift up and spin the tracks mid-air, one side is much faster than the other, and during tracking, there is a turn to one side,
I am expecting work case the slower motor is dying., but id’ like to rule out that I’m not running a hare on one motor, a tortoise on the other first.


The hare and tortoise modes, fast/slow,are these only for track speed, and what does this switch activate on/off, is it related to solenoids on the track motor pilot controls??

The switch does turn the green indicator on the dash panel, on/off, but there is no change in speed, to either motor, so what should this switch be activating, relay/solenod etc..

 

[willie59]

I'm not familiar at all with the dash 1 series of the EX120, I'll put that out right up front. It seems you have two problems. 1) motors tracking at different speeds, and 2) hi/lo speed not working. Let's say, your left drive is slower than your right drive, going forward. Is it the same going reverse, left slower than right? Secondly, I'm going to take a guess that the hi/low drive of the motors is done by changing the angle of the swash plate at the motors. If this is the case, you should have 4 hoses connecting each drive motor; 2 large lines for drive, 1 small line for hi/low speed change, and 1 small line for case drain. Update us on these tidbits of info and we'll try to take it from there and see if someone can help you out.

 

[cderekbower]

I'm not familiar at all with the dash 1 series of the EX120, I'll put that out right up front. It seems you have two problems. 1) motors tracking at different speeds, and 2) hi/lo speed not working. Let's say, your left drive is slower than your right drive, going forward. Is it the same going reverse, left slower than right? Secondly, I'm going to take a guess that the hi/low drive of the motors is done by changing the angle of the swash plate at the motors. If this is the case, you should have 4 hoses connecting each drive motor; 2 large lines for drive, 1 small line for hi/low speed change, and 1 small line for case drain. Update us on these tidbits of info and we'll try to take it from there and see if someone can help you out.

very kind of you to help the man out. some nice guys on these forums.

 

[danc]

some good folk on here alright,
Thanks for the input atcoequip...


Some futher detail …

The one motor is always slower both directions, there is a real obvious difference in speed, you don’t have to count sprocket rpms, it’s very clear., I’d say one is at least twice as fast as the other.
This is in either direction, and the same speed achieved by fast and slow motor in either direction, if you know what I mean, a constant difference.



From below the area around the swivel joint was all oily and wet, with oil drips, so I said I’d tackle this first.

I removed, stripped, resealed, and refitted the swivel joint, it’s now bone dry around this area, no drips.

The one motor is still slow.


The plumbing to the motors is as follows, from the swivel joint:

2 pipes per side to each motor., forward, reverse. Then a common pipe from the bottom plate of the swivel joint, is Tee’ed of to each motor (return?)
So 3 pipes per motor.

Without checking pressures I know this is a tough one, but any ideas welcome.

 

[cps]

Hi danc, Where abouts you based at?

It sounds like the small pipe is the leak return from the motors! although some have 2 small pipes one for the brake! Not sure how hitachi works!

If the small pipe is the leak return take it it of have someone move the track and see if a good bit of oil comes out of it!

Or it may be that you could have nipped a seal when you rebuild it the slew joint!

 

[danc]

yes the smaller pipe seems to be a return, it goes from each motor to a T just before it connects to the bottom of the swivel joint.

then 2 larger pipes to each motor.

I don't know what a flow from the small pipe will tell me if i can't be sure of what flow is going in, through the larger pipes.

would a large flow from the return indicate fluid passing motor seals or similar?

as far as a nipped swivel joint seal goes....the behaviour is just the same as prior to rebuilding the swivel joint, only no leakage from the joint now, so i'm hoping the joint is good, for now.

based in donegal...

 

[cps]

Yea a high flow would indicate trouble with your motor! seals or worse maybe (hopefully not) , there should be no more than a dripple if its ok!

Im from Near Cookstown in Tyrone, was up in the Downings Easter weekend!

 

[AtlasRob]

I'm not familiar at all with the dash 1 series of the EX120, I'll put that out right up front.

Neither am I, but I have learned something :drinkup

Yea a high flow would indicate trouble with your motor! seals or worse maybe (hopefully not) , there should be no more than a dripple if its ok!

Thanks cps, I did not know that. :notworthy

 

[danc]

so if i lift one side up , get the track turning at low engine rpms, with the pipe open, I should have only a dribble on the good motor.

So where does the 'working' fluid go creating the rotation, back through the other direction pipe?

so the 2 main pipes serve as supply and return, when reversed, the travel changes direction?

I had it in my head that one main pipe for forward, other for back, with the small pipe as return to tank, after the fluid has done its 'work'

I'll try it on the fast one first in case i get a flood from the other
thanks for the tip..

I'll check it out ...

 

[Cmark]

The flow is in a "loop". In through one hose, through the motor and out the other. This then reverses for the opposite direction. The small hose is a "case drain". It takes any internal leakage from the motor and sends it back to tank. It can be a rough indicator of motor condition. Large amounts of oil from the case drain = high internal leakage = not good.

However....

For your problem I would be looking at a pump flow issue. I am not at all familliar with your model, but I would guess that like most smaller HEX's there are two main work pumps. Generally, one pump supplies oil to the swing, dipper and one track. The other supplies boom, bucket and t'other track.

So...

I would suggest study the speed of the cylinders. At full rpm, compare the speed of cylinders controlled by the right joystick to those controlled by the left - any difference? Run each track in turn and operate a cylinder - any difference?

Can you post a photo of the pumps? I worked on an old Hitachi a long time ago and, from memory, each pump had a lever on the side to control the flow when an implement was operated.

Hope this helps.....

 

[danc]

the pipework to the motor makes sense now, the case drain similar to an engine crankcase breather somewhat..


I'll hopefully have her back together for the weekend for the pumps test you mention, good info... I'm changing some bottom rollers as well so some more bits to be fitted before a test drive..

My first excavator to drive and own so nothing to comapre to really, but I will do the trials mentioned, and post some pump pics too.

 

[cps]

The flow is in a "loop". In through one hose, through the motor and out the other. This then reverses for the opposite direction. The small hose is a "case drain". It takes any internal leakage from the motor and sends it back to tank. It can be a rough indicator of motor condition. Large amounts of oil from the case drain = high internal leakage = not good.

However....

For your problem I would be looking at a pump flow issue. I am not at all familliar with your model, but I would guess that like most smaller HEX's there are two main work pumps. Generally, one pump supplies oil to the swing, dipper and one track. The other supplies boom, bucket and t'other track.

So...

I would suggest study the speed of the cylinders. At full rpm, compare the speed of cylinders controlled by the right joystick to those controlled by the left - any difference? Run each track in turn and operate a cylinder - any difference?

Can you post a photo of the pumps? I worked on an old Hitachi a long time ago and, from memory, each pump had a lever on the side to control the flow when an implement was operated.

Hope this helps.....

To the best of my knowledge The ex120-1 have a single pump!

 

[lgp]

I spent a lot of hours on an EX100 -1 back in the late eighties/early nineties. That machine had two pumps. One for slew motor, dipper ram, and one track motor, the other for main lift rams, bucket ram and the other track motor. The travel speed switch on the dash (hare/tortoise) operated through a microcomputer and electro-magnetic valve along with the working mode and auto-idle switches, and appeared to govern the engine revs downwards on the "tortoise" setting for a slower travel speed. I never operated an EX120, but I would think it would be similar in layout.

 

[willie59]

Wow, you guys are all over this one before I could get back in here, rock on! I agree with checking the case drain on the slow motor. And if you only have 3 hoses at the motor, then the motor is fixed displacement and the speed change has to be done upstairs. I still leaning to that being a different problem, but we to do some testing on the slow motor first. The EX120-2 uses a single hydrostat pump, don't know if the dash 1 is the same.

 

[danc]

will hopefully get to do some tests over the weekend. took a few quick snaps before I headed to work.

motor had years of crap caked in behind the covers, a good clean up and paint required after i try and get things working better

 

[willie59]

Whoa, that does look like a double pump, although I can't say I've seen one quite like that one before.

 

[John C.]

Single speed motors and a double pump. As I recall those machines change travel speed by changing engine speed.

I have resealed about a half dozen swivels in EX200s. My first guess as to your problem would be that.

I didn't see in your posts if any other functions were slow. If you run a boom up cycle time it will pretty well tell you if your pumps are OK. Stretch the stick all the way out and put the bucket in the fully dumped position. Set it all on the ground, max out your engine speed and put in the fastest mode. Use a stop watch and time lifting the boom from the ground till it tops out. That should be around four seconds. It can run as high as five seconds and you will still be OK. If it's real slow then you could have a pump problem. Otherwise I'd pull that swivel apart first and reseal it.

Good Luck!

 

[danc]

Hey John, I’ll do a timed run on the boom, do you mean a boom lift while traveling or stationary?


The area around the swivel was wet, and I was hoping after resealing that the slow motor would have improved.
Anyway it’s not leaking around the swivel now, so I’m looking at other possibilities.

The fast/slow speed not working is obvious now after some studying of the plumbing, there is a bank of solenoids next to the pilot filter,that have been unplugged, one of these leads to the injector pump, so looks like these guys are controlling the fast/slow via engine speed alright.

Went to try a few response tests today, but the faster motor sprung a leak in the casing, at the centre of the casing where the hex bungs are for the frinal drive filler, level.

A square plate has been welded to this casing, not sure why, but the weld has sprung a leak, so must fix this first. Some day I’ll get there….

 

[danc]

Well things are not looking good on the fast motor now after it sprung a leak today

There was some dampness around where the blue line is for a while, and it was on my to-do list, but today when trying to troubleshooting the slow motor issue, the good side goes bad.

today a 4-5ft hydraulic leak came from the weld around the plate on the outer cover.
I’ve never seen inside one of these final drives, and trying to visualize how it works internally. I am thinking there should only be gear oil, and not hydraulic fluid in this part of the drive?
I didn’t get to removing the hex bungs, but I think this is now full of hydraulic fluid. I stopped the engine within a few seconds as I was looking down in that area at the time.
If this is a seal problem, is it common, and can it be resealed without special tools?

 

[John C.]

Seeing your photos and hearing your description I'd say the drive motor is shot. Your are correct that there should be gear oil in the sprocket side of the drive.

Basically you have to split the track and roll it off the final. Mark the relation of the hose connections on the motor with the track frame for when you reinstall the unit. Take out the ring of bolts that holds it in and you will need something to lift it clear.

I don't know what the parts situation is on those units these days but Hitachi was always pretty good for carrying them. I'm afraid you are going to find that there isn't much left inside that motor but shavings.

Good Luck!