120m

[wrench1]

my 120m grader blade drifts down on one side
thanks for any advice

 

[Nige]

Blade lift cylinder piston seals bypassing..?

What happens if you push the blade right down to the ground then continue so that you lift the front wheels just off the floor, then put the blade lift controls in neutral..?

 

[wrench1]

with the blade on the ground and the wheels in the air the blade holds
so maybe there is a check in the control valve ?

 

[Nige]

Not the cylinder if you can lift the front wheels off the ground and they stay there.

I wonder if the joystick for the LH blade lift cylinder needs calibrating..? The sensors in the joystick send signals to the control valve that in turn control solenoid valves that send the oil to the cylinder. Calibration requires Cat ET.

 

[lantraxco]

Hmmm, do they not have seals both ways on the piston Nige? I have seen cylinders drift in one direction and not the other....

 

[Nige]

Hmmm, do they not have seals both ways on the piston Nige? I have seen cylinders drift in one direction and not the other....

It's only a single seal Don. You'd think that if the cylinder would hold the weight of the front end of the machine in the air the piston seal would be good.

To the OP. Try this, get the blade in the air and drifting down on the LH side, then gently move the joystick just a hair away from the neutral position in the "up" direction. You may have to do nothing more than simply take the weight of the joystick lever with your hand. If you move it that hair does the downward drift of the blade stop..? Note: You may have to use the Monitor system to set the hydraulic control sensitivity to the Fine setting before you do this.

 

[Randy Krieg]

There is a “Temperature Compensating Line Relief Valve” in the lifting side of the circuit (barrel end of the cylinder). It’s designed to prevent a hydraulic hose failure if you dead head (pull it up hard and max out the pressure) the cylinder outside in cold weather and then move the machine inside a warm building. In this scenario you would have cold oil at +3500 psi in the hose going to the rod end of the cylinder, once inside the building the oil would start to warm and the pressure would increase slowly. The temperature compensating line reliefs are set to open at close to 3900 psi, which is below the burst pressure of the XT3 Hose. If you get a tiny piece of debris stuck under the valve seat or the seat gets damaged the moldboard will SLOWLY drop to the ground.

If the moldboard drops to the ground rapidly after releasing the lever then I would suspect the retaining plug for the flow compensation valve. This valve is right in the center of each compact control valve. To inspect the retaining plug you first have to put a vacuum on the tank so as not to lose too much oil and so you can view inside the port. The inspection plug is located right between the two hydraulic hose ports on each compact control valve. Once this plug is removed you can look in the port and see the retaining plug down in the port hole about 1 ½ inches. So on the 14 that did this repair on; the retaining plug (the one down in the port) had backed out enough that the lock check valve was hitting the top edge of retaining plug (the end you put the allen wrench in). So as fast as I would raise the moldboard it would drop back to ground even faster because the oil was dumping right back to tank.

Best Regards, Randy

 

[Randy Krieg]

Wrench1, That should have read (ROD END of the cylinder)in the first paragraph! Sorry about that. I had other projects going on last night and was rushing too much. Also the line relief valves are mounted right next to the electro motor which runs the spool. On most machines they are on both moldboard valves, centershift valve and ripper valve.
Best Regards, Randy

 

[Mark250]

Hi Wrench1 I am new to this but here goes if I muck up I apologize in advance
if blade drifts with engine off there are 4 possible causes
1.external (visible) leak
2.leaking cylinder seals
3.rod end line relief
4.lock check valves .
To eliminate check and line relief swap valves from right hand lift control valve section.
if lock checks and line relief are good lifting machine off the ground is not a good indicator of condition of cylinder seals.
Here are a couple of ways to check cylinder seals .
!/ release cylinder cap from ball, operate left joystick and extend cylinder to end of stroke remove hose from rod end of cylinder cap hose with steel ORFC steel plug, fit temporary hose to cylinder fitting to direct any bypass oil to a suitable catch bucket. operate joystick in same direction
If seals are ok not much oil will escape from cylinder. repeat test with rod retracted
Sometimes the cylinder barrel is belled out part way along cylinder length ,to check for this condition is quite easy but care is required do not use full pressure of hydraulics remove hose from piston end of cylinder cap cylinder port and hose end. Operate machine and attempt to move lift cylinder, if cylinder moves this indicates seal bypass at the position of the cylinder rod in the barrel if it doesn't move indicates seal is good
reposition the rod before capping and you can test different parts of the cylinder for bypass
Caution if the seals are good and the piston end is pressurised and rod end capped extremely high hydraulic oil pressure can be developed in the rod end of the cylinder and could cause the rod end seal to fail or personnel injury. An external relief should be fitted.
If blade drifts with machine running could also be calibration of left joystick go to cat messenger main menu scroll to service menu scroll to parameters scroll to implement scroll to blade L lift position this will give you a figure in % should be about 50% +/-5% with joystick centred anything higher than 55% or lower than 45% will need calibrating moving the joystick within these limits should produce no movement of lift cylinder
Regards
Mark250
PS I have a lot of info on m series but I don't seem to be able to post pictures but I can email if you like or if someone can help me through adding pictures screen shots and graphics

 

[Mark250]

m series menu selection and section of lift control valve

View attachment control valve SERV1840_SLD.pdfView attachment SERV1840_SLD.pdf