2 Komatsu Dozer D21A-6 Questions

rayspengler

New User
Komatsu D21a-6 Dozer with S/N 71019 trying to find out the year manufactured and the blade moves up and down fine, but blade will only turn to the right and lever lever piston will not retract to turn left... anyone with an idea?

Thanks, Ray
 
Loose piston on rod , allowing oil to bypass. Works one way because oil pushes piston against the rod and seals the leak.
 
Fritz
Thanks for the reply, but since I am new to dozers (not mechanics)... What piston on what rod? What is done to correct this?
Thanks, Ray
 
Assuming that there is no damaged linkage preventing moving the ‘angle’ valve back the other way … the angle cylinders are plumbed in a parallel criss-cross so one pushes while the other pulls. Any by-pass will render both cylinders inoperable.
Which cylinder? I would guess the one that is in extended is the culprit, since the oil would push the loose piston against the rod and seal the leak; trying to pull the rod back moves the piston away from the rod and all the pressure is lost through the bolt hole. The other cylinder can’t help because of the plumbing… the oil pressure for the piston end is also lost through the leak in the defective cylinder.
Only thing that can be done is break down the cylinder and re-pack it.
 
If you are talking about the large cylinders (2-3" in diameter), I'm not sure that we are on the same page on this.
When I checked out the dozer when I bought it everything worked fine. When I unloaded it from the trailer again everything worked fine.
When I went to move it a couple weeks ago, the handle (joystick) would move to the right and the blade would move to the right, but when I went to move the handle back to the left, the handle would not move to the left. Same with tilt..... I'll try to get a picture tomorrow
Thanks, Ray
 
Here is a photo of the suspected blade control unit
 

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