Hi All, I recently purchased an old komatsu pc50uu-1, about 7K hours. I resealed a couple hydraulic cylinders as the first issue to fix. Now when I go to move it around if I only pull on one lever to turn, it doesn't go. Left will work, but not right. Then if I pull on both of them it will track, even up a hill. If I let off of one lever both stop. I can have one in forward and one in reverse and they will do what they are supposed to, but not individually, except one side mostly does. The blade down force is also very weak. If you lift the machine with the boom then put the blade down it will hold the machine up no problem so I don't think that is internal to the cylinder. Given these symptoms my first thought is the center swivel joint is leaking internally. I don't see any fluid from below it, and the hydraulic tank is fairly full. Think I'm on the right track or should I look at other culprits? Keith
Good day It may be your central joint, is the lazy track in both directions or just one ? See attached if you need a more comprtehensive check drop a line here I will post one for you. Kind regards Uffex
I'm going to check, but I believe it was both directions. This machine has 3 hydraulic pumps and 3 valve blocks. One pump/block does swing, travel acceleration and blade. One does Boom, boom offset, bucket and Left drive. The final one does stick and right hand drive. If any of the pumps were bad I should have issues with the other functions on the same pump(I'm not positive I don't, given how little time I've had on it). I guess I should put it to work a bit to see what else I can find. I have to fix a fuel delivery issue before it will run for more than 10 minutes...
It seems that both tracks behave fairly similarly. Not much power when only one lever is pulled, but fine when both are pulled and in either direction. The travel acceleration seems to have an effect on speed. When both levers are used it can climb a 20% grade(estimated) without isssue. The swing is super weak. It won't swing either direction if it's slighly uphill. Down hill swing is no problem. I guess I'll go after the center swivel rebuild(seals) first to see where that leaves me. Then I'll try to figure out the swing issue. Guess I should get some pressure gauges to see input/output pressures to isolate issues more easily. Thanks, Keith
Update....It seems that the acceleration pedal was stuck engaged. When I pulled that out, the swing was working normally(same pump powers swing, blade and accelleration)...guess I should check the blade and track function now that I figured that out....