Pressure Relief Valve

PRESSURE RELIEF VALVE TROUBLESHOOT:

Power steering pumps have a built in spring-loaded pressure relief valve. This valve is designed to lower or stop hydraulic pump ¬†pressure when pressure reaches a preset value. You can observe this by steering to a full-turn of the vehicle’s steering limits or by attempting to turn the tire from a designated spot against an obstruction. Within the steering pump a valve will plunge and spring back without the driver’s awareness while turning. This valve design prevents overheating, and any potential hose or seal bursts.

If steering trouble occurs, the valve can be half or fully stuck within the valve bore of the pump. When half-stuck the driver¬†experiences lowered or a complete loss of pressure; a common symptom of this occurrence is difficulty while steering with the engine in idle. (However this does not not occur if the engine rises above idle by any couple hundred RPM, at this point the engine power causes an influx of fluid creating an easier turn.) To ensure whether the valve is half or fully stuck check for this occurrence. In the event a valve is fully stuck, all power steering will be lost and the vehicle’s steering will act as if the engine is off. GM Saginaw pumps see this problem far more frequent than other manufactured pumps.

These symptoms are observable with ALL and ANY pumps: old , new, or rebuilt.

The Common Solution: Diagnosing for any of these symptoms, and possible replacement.

Checking for such will require access to the pump’s pressure union fitting, where the power steering hose attaches to the pump.

assembled valve bore on pump1disassembled-valve-bore1

To begin this process:

  • Place a container underneath the vehicle to catch any fluid.
  • Remove the pressure hose at the power steering pump and move it away for drainage.
  • Next, remove the union fitting from the pump while being cautious approaching the final thread for any spring recoil. ( Most valves are loaded with + – 9 in. pounds spring. )
    • IF NO SPRING LOAD IS FELT: The valve is fully stuck and will require tapping with a flat punch and small hammer to dislodge the relief valve and spring from the stuck position.
  • Remove the valve and spring to inspect for burs and any slight debris within the housing. This bore and the valve itself maintain very tight tolerances, small particles and any wear may cause the valve to stick.
  • Using break cleaner or high-pressured air, clean out the valve bore and wipe the valve.
  • Once clean, reassemble the housing with the spring and valve and add fluid again.

Now follow Benchworks Steering System’s instructions for bleeding!