Test Procedure

Fig 1: Identifying Power Steering System Components

Courtesy of ISUZU MOTOR CO.

Test of fluid pressure in the power steering system is performed to determine whether or not the oil pump and power steering unit are functioning normally.

The power steering system test is used to identify and isolate hydraulic circuit difficulties. Prior to performing this test, the following inspections and corrections, if necessary, must be made.

• Inspect pump reservoir for proper fluid level.
• Inspect pump belt for proper tension.
• Inspect pump driver pulley condition.
  1. Place a container under the pump to catch the fluid when disconnecting or connecting the hoses.
  2. With the engine NOT running, disconnect the pressure hose at the power steering pump and install power steering tester J-29877-A. The gage must be between the shutoff valve and pump. Open the shutoff valve.
  3. Check the fluid level. Fill the reservoir with power steering fluid, to the "Full" mark. Start the engine, then turn the steering wheel and momentarily hold it against a stop (right or left). Turn the engine off and check the connections at tester for leakage.
  4. Bleed the system. Refer to BLEEDING THE POWER STEERING SYSTEM .
  5. Start the engine and check the fluid level. Add power steering fluid if required. When the engine is at normal operating temperature, increase engine speed to 1500 rpm.
     CAUTION: Do not leave shutoff valve fully closed for more than 5 seconds, as the pump could become damaged internally.
  6. Fully close the shutoff valve. Record the highest pressures.
     • If the pressure recorded is within 9300-9800 kPa (1350-1420 psi), the pump is functioning within its specifications.
     • If the pressure recorded is higher than 9800 kPa (1420 psi), the valve in the pump is defective.
     • If the pressure recorded is lower than 9300 kPa (1350 psi), the valve or the rotating group in the pump is defective.
  7. If the pump pressures are within specifications, leave the valve open and turn (or have someone else turn) the steering wheel fully in both directions. Record the highest pressures and compare with the maximum pump pressure recorded in step 6. If this pressure cannot be built in either side of the power steering unit, the power steering unit is leaking internally and must be replaced.
  8. Shut the engine off, remove the testing gauge.
  9. Reconnect the pressure hose, check the fluid level and make the needed repairs.
  10. If the problem still exists, the steering and front suspension must be thoroughly examined.