Daewoo GC20S-3, serial 95-00571. Originally called out for no power steering. I thought the orbitrol was bad, so I replaced it. Still no steering. Checked pressure on inlet side of the orbitrol. It is at 100 +/- 50 pounds. No change when trying to turn the steering wheel. Rebuilt the brake valve with new seal kit. Still no steering. Inspected steer cylinder, no visible external leaks. Bypass the brake valve and hooked the orbitrol straight to the pump. Still no steering. At this point I am at a loss. The brakes work fine as well as the other hydraulics. Has anyone had this problem before?
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Good to hear you found the issue and got it going.......
Pulled the priority valve, found no trash and the valve seemed to be moving freely. I assumed the steering side of the pump was bad. Pulled the pump. Was able to turn the shaft by finger. I knew right away the pump was no good. Replaced pump. Steering now ok.
Thanks again Kevin. I really appreciate your help on this one.
Kevin, that information is priceless. I will pull the priority valve and check it. Thanks a million.
Sounds like the priority valve on the hydraulic pump the spool is sticking(stuck open)....should have 150 PSI for the load sensing sytem to open the spool for oil flow to the steer orbitol.....following is for the sytem
The steering system is a load sensing closed center type and uses hydraulic oil for its operation. Oil flow through the steering system is closed unless the steering wheel is turned. The flow through the steering gear is sensed by the priority valve, which then allows additional oil flow to the steering system. The priority valve also fills the requirements of the power brakes (if equipped) and then the mast.
Hydraulic oil is pulled from hydraulic tank (17) through a strainer to hydraulic pump (16). The pump sends the oil through hose (7) to brake valve (3). When the steering gear and brake valve are in NEUTRAL position, pressure in hose (15) and the priority valve internal sensing line rises to 1035 kPa (150 psi). When this pressure is at least 1035 kPa (150 psi) more than load sensing signal hose (12) the priority valve metering spool shifts to stop oil flow to the steer gear.
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