Hitachi UH122

[etd66ss]

I can only find a parts list online for a UH123 center joint, but looks very similar:



Oil is coming out right at item 11, which looks like a bearing race.

 

[Welder Dave]

UH series were very popular in N America. They are what established Hitachi as the best selling excavators in the day.

 

[Tones]

UH series were very popular in N America. They are what established Hitachi as the best selling excavators in the day.

Not just N America but globally. In NZ they had 96% of the excavator market. Contractors who ran a 100% Cat fleet went straight to Hitachi when they got into excavators.

 

[etd66ss]

UH series were very popular in N America. They are what established Hitachi as the best selling excavators in the day.

Then I guess it is strange I can buy any part I need for my 1978 CAT 225, but this (1985?) UH122 looks pretty impossible to find parts for, so far...

Also, should I assume all the pipe threads on the air tank are BSPP? I have some tank filling valves that I can used wiht a tire air hosem but they are 1/4 male NPT. Not sure I can fint BSPP stuff by tomorrow when I try to start this thing.

 

[Welder Dave]

1 out every 4 excavators sold was an Hitachi back in the day of the UH series machines. I think a thread pitch gauge would be a great asset to figure out what fittings your machine has. I'm not sure a Japanese machine would have BSPP fittings. I'm really curious if you've talked to an Hitachi dealer. Being that Hitachi are still very popular it seems like a long term dealer should be able to help you with a key and what size fittings your machine has.

 

[etd66ss]

I described the bleed process in an earlier post.

Ok, so tonight I got the following done:

1) Installed a new fuel filter, and put in 10 gallons of fresh fuel.

2) I primed the system with the hand pump, bled the top of the filter housing of all of its air. Not sure the plunger is working all that great. I can build up some serious pressure when I prime my CAT 3208 in my 225 with the hand plunger, so much so that I can't push the plunger and further. This machine, I hear some kind of relief valve after using the plunger for a bit, never feels like it builds any pressure. Do I need to crack loose the nuts on the injectors and bleed each one individually?

3) I harvested 35 gallons of oil from the Daewoo excavator and put it in the UH122. I was monitoring the sight glass and the last 5 gallon bucket put me to the second red line, I assume the level is supposed to be between the two red lines with the boom and stick fully extended and on the ground, so there may be a bit too much oil.

4) I then checked the bleeder screws on the main pump housings.




When I cracked them loose they both were full to the plug level. So I assume this means I don't have to manually pressurize the air tank before starting, I can start as-is and let it idle to see if the air pump is working via the gage in the cab?

Here is a video of the top pump bleeder port when opened up: Top Pump Bleed

4) I greased the fitting in the main pump gearbox:



5) I checked oil level of the main pump gearbox, it seemed way over full. But the only plug seemed very low, so not sure I was using the correct level plug:



Maybe HYD oil is leaking into the gear pump housing via a bad seal...

6) I checked both planetary gearboxes, the LH one was almost full to the correct level, the RH one however was very low, about 2.5" below the level plug hole.

7) I put more grease into the LH slack adjuster, I got to a point where the track won't fall off the front idler, but I have now put in 3 tubes of grease. There must be a bad seal as I am not really building up pressure like I can on the RH slack adjuster. I don't see grease oozing out anywhere, but that piston is pretty well hidden in the track frame, so not sure I could see that anywhere.

8) I received the new ignition switch from Amazon. That will be the first thing I try tomorrow.

Previously when I wanted to use my starter trigger to crank the engine over, I had to disconnect the battery relay because I assume the batteries are disconnected until the ignition is turned to the on position? So I should connect that back up when I install the new ignition switch?

I think I am ready to try to start this thing tomorrow.

 

[skyking1]

That track would be really hard to adjust stuck down to the ground like that. Keep that in mind. It is always easier to lift that side, and that is also the method for setting the slack properly on our 120, for example.
It sounds like you are ready to give it a whirl. Best of luck to you!

 

[Welder Dave]

Might be a good idea to spin it over with the fuel shut off to get some oil circulated before starting. That's what I was told after my engine was rebuilt.

 

[etd66ss]

I got the machine running but wnen I went to drain the air tank it is full of hyd oil. Any ideas on that?

 

[Welder Dave]

I wonder if there's a check valve on the air tank that's maybe faulty? Other thought is over time hyd. oil was siphoned into the air tank from temp. changes or a negative pressure on the air tank.
Give some more details on getting it running. Did it smoke and how did it run, did it make weird noises etc. How long did you run it?

 

[skyking1]

Bonus, you found more hydraulic oil!!
I think you need to get the correct level in the tank and then check it out. Did you get air pressure?

 

[etd66ss]

Ok, so to airline from the compressor to the tank was bad. I guess the main pumps were filling the tank because there was no air pressure?

I fixed the airline, draining the air tank of the oil and will try again.

The oil level on the sight glass went down about 1/2 in. So I know where that oil went...

 

[etd66ss]

I wonder if there's a check valve on the air tank that's maybe faulty? Other thought is over time hyd. oil was siphoned into the air tank from temp. changes or a negative pressure on the air tank.
Give some more details on getting it running. Did it smoke and how did it run, did it make weird noises etc. How long did you run it?

I got the new ignition switch installed and put all new fuses in the fuse panel I started cranking to get oil circulated. About after 1 minute of that cranking it started puffing seriously black smoke from that nasty varnished fuel left in the injector pump.

Tried about two more times and it was wanting to start but wasn't, so I moved the throttle lever to halfway and it started. No either required. Once the varnish was out of the pump the exhaust cleared right up. It seems to run smooth and on all 6 cylinders.

 

[Welder Dave]

Generally if a diesel is hard starting and/or cold you give it full throttle so it gets as much fuel as possible. Once it starts slow it down to around 1000 rpm's. I knew a guy who loved the Isuzu engines in his UH122's and a 121. 121 didn't have live swing.

 

[Acoals]

Once it starts slow it down to around 1000 rpm's.

I sure as anything wouldn't start slowing things down to 1000 rpm on a cold start. You start pulling the throttle back as soon as it starts popping. I wouldn't let it get past normal idle speed until it has run for a minute or two, or at least until you have full oil pressure and it has smoothed out.

 

[Tones]

I'm surprised that engine hasn't got glow plugs.
Well done on the work so far.

 

[skyking1]

^ well done indeed.
with regards to leaking, I have seen more than a few examples of stuff sealing back up with some use.

 

[Welder Dave]

I sure as anything wouldn't start slowing things down to 1000 rpm on a cold start. You start pulling the throttle back as soon as it starts popping. I wouldn't let it get past normal idle speed until it has run for a minute or two, or at least until you have full oil pressure and it has smoothed out.

It depends on the engine. I had Hino that was very warm blooded. To start in cold weather had to use the glow plugs 3 times and full throttle. Once it started you had to keep it at full throttle until it got up to about 1200 RPM, then you could let off the throttle and it would idle. If you let off the throttle too soon it would die. I'm not saying to let it rev higher and then slow it down. I'm saying let it get up to about 1000 RPM and then back off the throttle. The Kubota in my skid steer starts much easier with the throttle set at full but as soon as it's running on its own you can throttle it back. I don't think it even gets to 1000 RPM. A lot of manuals will also say to put the throttle to full for starting when cold. It doesn't mean start it and let it rev to the moon. The throttle at full just let's it get the most fuel to ignite.

 

[etd66ss]

OK, so the air hose I fixed was not for the tank, I heard a sound while the machine was idling scared me as I thought something was siezing up, turns out it was the air horn coming to life...

I did move the machine about 20 ft. I had to rev it up a bit to get the implements working, I would make a small move shut it down to keep checking the main pump bleed plugs, the pumps always stayed full of oil.

Here is a start vid after I had the machine running for about 30 minutes and after moving. It also shows the oil in the air tank issue, and you can hear the air leaking out of the canister under the engine: UH122-Start

Here's a video of the air compressor after I switched the hose from the right port which had no air coming out of it to the left port: UH122 Air Compressor

And this video shows that I think I have this air canister plumbed wrong: UH122 Air Canister

This piece of old HYD hose was jammed on the air compressor port that has pressure coming out:


I mistakenly hooked it up to what I thought was a line that would feed the tank, but went to the air horn. I was wondering why the connection coming out of this was for 3/8" air brake hose and where I connected it up was 1/4". I thought maybe there was a reducing union at some point in time.

When I removed that hose and connected the one going to the canister, that's when I heard air leaking out of the relief valve in that last video. When I took that video I noticed a piece of 3/8" air brake hose that was sheared off, it leads to a port on the bottom of that canister. So maybe that is supposed to be the air supply to the canister? This is not simple, there are damaged air lines going all over the place, it's not as simple as one line going from the compressor to a regulator then to the tank...

Here is what the plumbing looks like tot he HYD tank:




I'm wondering if I can bypass all of the other pneumatic equipment and connect the compressor to the left side of that regulator to pressurize the tank?

I still don't understand how the oil is getting into the air tank when that bung hole is so high up, much higher than the oil level in the tank.

This is how much the oil in the HYD tank went down, it started at the top red line:



It seems like a lot of the implements had air in them as they took a while to activate. I suspect that's where mot of the oil went. I lost about 1 gallon out of the leaking center joint while I messed with this thing. Total runtime was about 45 minutes to an hour, mostly at idle.

 

[Welder Dave]

You really need to get some manuals or at least hyd. and air schematics. Great you got it running but that should have just been to see if the engine is OK. You could be causing more damage to other systems by continuing to run it without knowing what's leaking or or how the hoses are supposed to be hooked up.