Fluid Pressure Check

1. Disconnect pressure line joint using power steering line wrench tool No. 09631-22020 or equivalent.

Fig. 1 Connecting Oil Pressure Gauge:

2. Connect the gauge side of a suitable pressure gauge to the pump side and the valve side of gauge to gear housing, Fig. 1.
3. Bleed power steering system as outlined under BLEEDING POWER STEERING SYSTEM.
4. Check and adjust fluid level.
5. Raise fluid temperature by turning the steering wheel from stop to stop. Fluid temperature should be 176°F.
6. Start and run engine.
7. Minimum fluid pressure reading with valve closed should be 1067 psi on ES 250, SC 300, SC 400 and LS 400, and 1351 psi on ES 300. Do not keep valve closed for more than ten seconds or allow fluid temperature become too high.
8. If pressure is low, repair or replace the power steering pump.
9. With valve open fully, check and record pressure reading with engine at 1000 RPM.
10. With valve open fully, check and record pressure reading with engine at 3000 RPM.
11. Ensure there is 71 psi or less difference in pressure between the 1000 RPM and 3000 RPM checks. If difference is excessive, repair or replace the flow control valve of the pump.
12. Check pressure reading with steering wheel turned to full stop position as follows:
a. Ensure pressure gauge valve is fully open and the engine idling.
b. Minimum pressure with steering wheel turned to full stop should be 1067 psi on ES 250, SC 300, SC 400 and LS 400, and 1351 psi on ES 300,. If pressure is low, the gear housing has an internal leak and must be repaired or replaced. Do not keep valve on gauge closed longer than 10 seconds or allow fluid temperature to become too high.
13. Remove pressure gauge from system. Bleed system and check fluid level.
14. Measure steering effort as follows:
a. Center steering wheel and run engine at idle.
b. Using a suitable spring gauge, measure steering wheel effort in both directions.
c. If steering wheel effort is not less than 6.6 lbs. on ES 250, 7.7 lbs. on ES 300, 9.0 lbs. on SC 300 and SC 400, and 8.8 lbs. on LS 400, repair or replace the power steering unit. Consider tire type, pressure and contact surface when making your diagnosis.
d. Disconnect solenoid connector.
e. Measure steering effort as done in steps a through c.
f. Maximum steering effort should not exceed 15.4 lbs. on ES 250 and LS 400, 17.6 lbs. on ES 300, and 17.0 lbs on SC 300 and SC 400. If steering effort is not more than reading found in step c, check the solenoid.