• Thank you for visiting HeavyEquipmentForums.com! Our objective is to provide industry professionals a place to gather to exchange questions, answers and ideas. We welcome you to register using the "Register" icon at the top of the page. We'd appreciate any help you can offer in spreading the word of our new site. The more members that join, the bigger resource for all to enjoy. Thank you!

Komatsu PC50uu-1 hydraulic problem

John C.

Senior Member
Joined
Jun 11, 2007
Messages
12,865
Location
Northwest
Occupation
Machinery & Equipment Appraiser
You can test the glow plugs with an ohm meter. A good plug will show some resistance through it. A bad plug will be shorted through, ohm meter will show zero resistance, or open circuit, ohm meter will not move. You can test them in place and use the engine block for ground for the test.
 

komatsugreg

Member
Joined
Jul 20, 2017
Messages
24
Location
Creston BC
Thanks very much I'll give that a go, If they have to be replaced, do you know of a supplier?
I'm thinking FridayParts may have them but am always open to different channels.
 

komatsugreg

Member
Joined
Jul 20, 2017
Messages
24
Location
Creston BC
Found the problem(s)
The glow plugs are connected by a tin bar that runs across their heads and are held in place by nuts.
There were no lock washers on the nuts and they vibrated lose - just enough to cause a resistance from corrosion
and prevent the plugs from getting full current,
 

John C.

Senior Member
Joined
Jun 11, 2007
Messages
12,865
Location
Northwest
Occupation
Machinery & Equipment Appraiser
Glad to hear it. Another quick test to see a short plug is that the bar will be discolored just ahead of the shorted plug. I usually throw the lock washers away. They don't do anything but give you the type of problems you just found.

Nice Work!
 

wildfire

New Member
Joined
Feb 27, 2018
Messages
3
Location
Vancouver Island
Sorry to hijack this thread. But it appears to be the only active PC50uu-1 group out there. I've very recently picked one up, about 3500hrs, steel track with full cab (blown out front windscreen and homemade bent up door). Everything seems strong so far.

The left joystick controls are non-ISO and would like to switch the existing stick-swing control set-up around to ISO.
  • Left hand left = Swing left.
  • Left hand right = Swing right.
  • left hand forward = Stick Boom (Dipper) away.
  • Left hand back = Stick Boom (Dipper) close.
Currently it is.
Left Hand left = Stick away
Left hand right = Stick in
Left hand forward = Swing right
Left hand back = Swing left.
Have any of you switched to ISO controls and if so how? It doesn't appear to be as easy as I had though it would be once pulling the covers and looking at the array of push rod/bell cranks and two separate spool valve packs. Maybe just get use to existing controls.

I'm looking for PDF service/shop manuals, but the sites offering them look dodgy, anyone had success with any of them for their service manuals?

Sounds like the hydraulic oil is 30w non-detergent as well as the swing motor gear case but how about the final drives? Heavy gear oil or the same 30w as everything else? I'd really like to do a fluids change before (especially final drives) before working machine. Big thanks to everyone who has posted there. Greg your pic's for the thumb install and plumbing plus the part numbers for the hydraulic filters is perfect, Thanks again.
 

John C.

Senior Member
Joined
Jun 11, 2007
Messages
12,865
Location
Northwest
Occupation
Machinery & Equipment Appraiser
I've never seen a Komatsu spec show 30w non-detergent oil for the hydraulic system. What I have used in all the Komatsu excavators I have worked on was an AWS 46 hydraulic oil. All the gear train stuff in the past was 30 wt. engine oil. In my experience it isn't very easy to find non-detergent oils now days.

Your description of the controls sounds like you have a manual controlled machine and not a pilot operated one. Some photos of the cab and linkages would be helpful. If it has manual controls it is a lot of work with cutting linkages and repositioning bell cranks to make the change. If it is a pilot operated machine it just involves swapping some pilot hoses.
 

apm

Well-Known Member
Joined
Apr 1, 2011
Messages
171
Location
Northeast Tennessee
Sorry to hijack this thread. But it appears to be the only active PC50uu-1 group out there. I've very recently picked one up, about 3500hrs, steel track with full cab (blown out front windscreen and homemade bent up door). Everything seems strong so far.

The left joystick controls are non-ISO and would like to switch the existing stick-swing control set-up around to ISO.
  • Left hand left = Swing left.
  • Left hand right = Swing right.
  • left hand forward = Stick Boom (Dipper) away.
  • Left hand back = Stick Boom (Dipper) close.
Currently it is.
Left Hand left = Stick away
Left hand right = Stick in
Left hand forward = Swing right
Left hand back = Swing left.
Have any of you switched to ISO controls and if so how? It doesn't appear to be as easy as I had though it would be once pulling the covers and looking at the array of push rod/bell cranks and two separate spool valve packs. Maybe just get use to existing controls.

I'm looking for PDF service/shop manuals, but the sites offering them look dodgy, anyone had success with any of them for their service manuals?

Sounds like the hydraulic oil is 30w non-detergent as well as the swing motor gear case but how about the final drives? Heavy gear oil or the same 30w as everything else? I'd really like to do a fluids change before (especially final drives) before working machine. Big thanks to everyone who has posted there. Greg your pic's for the thumb install and plumbing plus the part numbers for the hydraulic filters is perfect, Thanks again.

The Komatsu manual for the PC50UU-1 does in fact specify 30W non detergent for virtually the entire system, including the final drives.

From memory, it seems like there were mechanical provisions for changing patterns. It is not a pilot system. I will go through the manual and see if I can find what I think I'm remembering.

I did download a manual from one of those sites, it worked well. I can try to email you the PDF if you like.
 

John C.

Senior Member
Joined
Jun 11, 2007
Messages
12,865
Location
Northwest
Occupation
Machinery & Equipment Appraiser
I'm thinking it must be an old gray market machine then. Any idea of what year it is?
 

wildfire

New Member
Joined
Feb 27, 2018
Messages
3
Location
Vancouver Island
Thanks for the reply's.
Yes it is an old gray market. Not sure the year but it's serial 5840, guessing late 80's early 90's.
I received this morning, a PDF Shop Manual emailed on to me by another member on the forum here tool_king. Huge shout out to him for that, trying to figure out how to buy him a beer from across the border. I'll pour over it and see what I can find for swapping controls over. I did find on another equipment forum a member mention he swapped his controls over on his old pc50uu-1 by swapping the lines coming off the spool valves ... and he didn't have any issues with hydraulic flow. That said, I could see that potentially being a problem and have been advised that I really want to swap at the linkages (mechanical) not the spool valves and there should be a way.

I'll post back with what I find and how it works out. Sure appreciate your thoughts.
 

wildfire

New Member
Joined
Feb 27, 2018
Messages
3
Location
Vancouver Island
Alright, figured it out.

This version of the pc50uu-1 has a square bolt with one side shaped to an (indicator) arrow, at the base of the left hand pedestal. Inside of pedestal it was a simple lever pointed into the bell crank cluster. Of course with it at floor level any markings were obliterated and looking down on it from inspection plate removed on side of pedestal I assumed it was some kind of manual control lock out that had been disconnected (turns out the actual control lock out has been completely cut away), as it wasn't nested into a slide plate which sits on top of bell crank cluster. The clue I missed was that there were two push rods coming off the fore/aft of the left joystick; one actuated a bell crank connected to spool valve (at this time the swing) and the other was hooked up to a non-functional bell crank on the oppose side of the shaft the bell cranks pivot on. I assumed the non-functioning one was some kind of mass balance or stabilizer.

Well after tearing pedestal apart and getting my hand under the "slide plate" realized there were tabs on the top of two of the bell cranks that the slide would flip 90degree to engage or disengage adjacent bell cranks; thereby changing controls from old school Japanese to ISO controls. Kind of ingenious but as the control selector wasn't hooked up to the bell crank slide I would of had to tear it apart anyways. And be forewarned, I had a heck of time getting the pedestal back over the push rod cluster, in the end I had to leave the fore/aft push rods attached to the main joystick knuckle, the side to side push rod disconnected at the push rod turn buckle. Dropped the pedestal onto the joystick, attached the fore/aft knuckle to pedestal then dropped the side to side upper pushrod with knuckle down into the main knuckle from above and pined it in place while reattaching at the turnbuckle. I'm assuming it was do to the lack of space and difficultly in reinstalling pedestal that a previous owner cut the control lock out off.

Pics show the slide plate on top of the bell crank cluster, tabs to "flip' between different bell cranks located under it. And the mystery indicator/selector at base of pedestal.

IMG_8059.JPGIMG_8058.JPG
 

apm

Well-Known Member
Joined
Apr 1, 2011
Messages
171
Location
Northeast Tennessee
Congratulations for sticking with it and figuring it out. It is supposed to be a simple mechanical changeover, then. It sounds like you were able to accomplish your goal even if it was more than you initially intended to get into. Now you'll be able to point the next guy in the right direction!

Greg
 

tool_king

Senior Member
Joined
Mar 29, 2010
Messages
2,145
Location
new jersey
Occupation
road mechanic owner
Wildfire
Glad it worked out for you .It is always great when you can get you machine back up and running.
 

jeeperjake

Member
Joined
Oct 15, 2019
Messages
9
Location
Washington
Hello, I am brand new to the site and a new owner of 2 Komatsu PC50uu-1 excavators. Both have been sitting for years. One runs and the other needs some help and possibly parts if the previous owner doesn't find everything. May end up being a parts machine, but I'd like to get both going! I was hoping to get some general info regarding these machines.

1st, Would someone be willing to share the PDF manuals discussed earlier in this post?
2nd, Any help regarding where you have had luck getting parts. Local, foreign, online. Are dealers helpful with these grey market machines? Any scrap yards parting them out?

Hopefully I am not hijacking this thread, but it seems to be a general thread for PC50uu's

Thanks
 

John C.

Senior Member
Joined
Jun 11, 2007
Messages
12,865
Location
Northwest
Occupation
Machinery & Equipment Appraiser
I don't recall that a lot of those came into the country back then. All the mini Komatsu excavators were a little bit different than the larger ones. Most that I have had the occasion to work on had Yanmar engines in them. The pumps were gear or maybe one gear pump and a piston pump. The valves all worked differently. Maybe a photo or two might help jog a memory or two.
 

jeeperjake

Member
Joined
Oct 15, 2019
Messages
9
Location
Washington
IMG_2039[1].JPG IMG_2038[1].JPG IMG_2025[1].JPG
I know those are not very good pictures, but maybe you'll get the idea. I don't even have the yellow (running) one home yet.
 

John C.

Senior Member
Joined
Jun 11, 2007
Messages
12,865
Location
Northwest
Occupation
Machinery & Equipment Appraiser
Those are articulating boom units. I don't see the potentiometers for the stick or boom so you might be OK to run them here. I see a lot of hoses capped off on the green machine. I've never had the "pleasure" of working on one of those. You should be able to get any parts you need from the Komatsu dealer. Just give them a serial number.
 

jeeperjake

Member
Joined
Oct 15, 2019
Messages
9
Location
Washington
Those are articulating boom units. I don't see the potentiometers for the stick or boom so you might be OK to run them here. I see a lot of hoses capped off on the green machine. I've never had the "pleasure" of working on one of those. You should be able to get any parts you need from the Komatsu dealer. Just give them a serial number.

The green machine has the swing motor and gearbox removed, so there are lines unhooked just laying there. The idea was to get a machine with a parts machine and hopefully be able to keep one good machine with an extra of eveerything, but if I can get both running for a reasonable price, then I may do that.
 

John C.

Senior Member
Joined
Jun 11, 2007
Messages
12,865
Location
Northwest
Occupation
Machinery & Equipment Appraiser
What general area of Washington are you in?
 

John C.

Senior Member
Joined
Jun 11, 2007
Messages
12,865
Location
Northwest
Occupation
Machinery & Equipment Appraiser
I only get through that area once in awhile. You might have to settle on making one machine out of two. You are right about the parts and maybe you can find a machine knocked in the head for more parts to get the second one running. New parts will be very expensive.
 
Top