ABD

[ABD]

HI, I OWN A 1993 J.D.SKID STEER IT HAS BEEN MINE SINCE 1996. THEN IN 2002 IT STARTED GIVING ME HYDROSTATIC CHARGE PROBLEMS AT 1800HRS AND ITS STILL THE SAME TODAY WITH 2100HRS. I HAVE CHANGED THE CHARGE PUMP 2 TIMES AND RAN ALL SORTS OF PRESSURE TEST ON IT. MY LOCAL J.D./ NEW HOLLAND DEALER DOES NOT HAVE A CLUE TO WHAT THE PROBLEM IS,THEY TELL ME ITS A COMBONATION OF METAL WEAR INSIDE THE 4 HYDROLIC PUMPS/MOTORS. I CAN NOT SEE IT, THE DRIVE HAS LOTS OF POWER UNTIL I USE THE BOOM AND THE BOOM HAS POWER UNTIL I USE THE DRIVES.
I HAVE CHANGED RELIEF VALVES, FILTERS, FLUIDS SUCTION LINE PRESSURE LINES AND OTHER STUFF THAT DIFFERENT TECHNICIANS HAVE THOUGHT TO BE THE PROBLEM.
I NEED SOME ADVICE AND BE PATIENT WITH ME ON HOW TO USE THE FORUM.

THAX AARON

 

[chasBOMAG]

Sounds like your hydraulic system is having trouble keeping up with the flowrates required by the drive and boom circuits. Does the machine still reach pressure relief settings?

Without a hydraulic print of the skidsteer its hard to determine a proper way to narrow down the problem. It seems the charge pump is keeping both the drive circuits supplied as well as the circuit which runs the boom. i would bet that the drives have worn to a point where their circuits require a significant flow out of the charge pump just to maintain the base pressure. this would affect the whole machine. hydraulic temps would rise and the performance would decrease as you have mentioned. (i would assume that the charging system comprises of a bypass set for somewhere around 200psi, and some flowrate say 5gpm. As the drives wear, they will consume more oil from the charge loop, thus depleting the charge pump capability to a point where it can no longer keep up. low charge pressure = high charge flow...) Is it possible to schroeder the charge pump itself? It would be beneficial to see how much oil the charge pump is throwing at the drives, then compare this to the factory baseline.

Swapping hydraulic components is an expensive troubleshooting technique, your mechanic should rely on good test gauges and meters.

 

[ABD]

Sounds like your hydraulic system is having trouble keeping up with the flowrates required by the drive and boom circuits. Does the machine still reach pressure relief settings?

Without a hydraulic print of the skidsteer its hard to determine a proper way to narrow down the problem. It seems the charge pump is keeping both the drive circuits supplied as well as the circuit which runs the boom. i would bet that the drives have worn to a point where their circuits require a significant flow out of the charge pump just to maintain the base pressure. this would affect the whole machine. hydraulic temps would rise and the performance would decrease as you have mentioned. (i would assume that the charging system comprises of a bypass set for somewhere around 200psi, and some flowrate say 5gpm. As the drives wear, they will consume more oil from the charge loop, thus depleting the charge pump capability to a point where it can no longer keep up. low charge pressure = high charge flow...) Is it possible to schroeder the charge pump itself? It would be beneficial to see how much oil the charge pump is throwing at the drives, then compare this to the factory baseline.

Swapping hydraulic components is an expensive troubleshooting technique, your mechanic should rely on good test gauges and meters.

THAX FOR THE REPLY. ALTHOUGH I HAVE REPLACED THE DRIVE MOTORS WITH NEWLY REBUILT ONES. BEFORE I REPLACED THEM I PERFORMED A CASE DRAIN TEST ON THE OLD ONES AND THEY WERE IN OPERATING RANGE OF FLUID LOSS...THE CHARGE PUMP FROM THE FACTORY WILL PU OUT 12GPM NEW AND I HAVE REPLACED IT 2 TIMES,THE SECOND TIME I BAUGHT 1 FROM MOTION INDUSTRIES THAT WILL PUT OUT 16GPM THIS ONLY MADE MY BOOM AND BUCKET WORK FASTER. IT DID NOT SUPPLY ANY MORE FLUID TO THE DRIVES AT ANY TIME. THE FUNNY THING IS THAT I HAVE POWER TO THE DRIVES UNTIL I USE THE BOOM OR I HAVE POWER TO THE BOOM UNTIL I USE THE DRIVES. AT BOTH TIMES THE HYDROSTATIC CHARGE LIGHT COMES ON AND I GOT TO QUIT ONE OF THE 2 TO GET IT TO GO OFF??????
I HAVE PERFORMED ALL THE PRESSURE TEST THAT THE FACTORY BOOK CALLS 4 BECAUSE I HAVE THE BOOK...

 

[chasBOMAG]

Something is using up all of your flow or is starving the system. only when both circuits are used the power is decreased. The flow has to be going somewhere: boom cylinders with bypassing seals, an auxillary valve for a pto provision that is stuck slightly, or maybe the flowrate is reduced to begin with from a collasped suction line... (sometimes hard to spot, the inner lining can separate from the plys and fold in on itself, then spring back whenever the pump is shut off)

Post the hydraulic print if you can