Symptom Related Diagnostic Procedures
INTRODUCTION TO POWER STEERING DIAGNOSISHydraulic power steering is used for all vehicles. Faults in the power steering can include excessive play of the steering wheel, difficult steering wheel operation, noise, vibration, and oil leaks, etc. Possible causes of these faults can include defects in the pear box, oil pump or steering linkage.
POWER STEERING DIAGNOSTIC TROUBLESHOOTING STRATEGY
Use these steps to plan your diagnostic strategy. If you follow them carefully, you will be sure that you have exhausted most of the possible ways to find a power steering fault.
1. Gather information from the customer.
2. Verify that the condition described by the customer exists.
3. Find the malfunction by following the Symptom Chart.
4. Verify malfunction is eliminated.
SYMPTOM CHART
SYMPTOM PROCEDURES
Inspection Procedure 1
Excessive Play Of Steering Wheel
DIAGNOSIS
STEP 1. Check For Looseness At The Steering Shaft Coupling Section And At The Steering Wheel Linkage.
If faulty, repair or replace the part. Then go to Step 3.
If normal, go to Step 2.
STEP 2. Check The Steering Gear Backlash (Excessive).
1. Jack up the vehicle front and hold the steering wheel in the straight ahead position.
2. Take apart the pitman arm and the relay rod.
3. Measure the steering gear backlash at the pitman arm top end with a dial indicator.
Limit: 0.5 mm (0.02 inch)
4. If the measured value exceeds the limit, screw in the steering gear box adjusting bolt until the steering wheel free play is within the standard value.
Then go to Step 3.
NOTE: Be sure to adjust with the steering wheel in the straight ahead position.
NOTE: If the adjusting bolt is overtightened, more steering effort will be required, and return of the wheel will be adversely affected.
STEP 3. Check Steering Wheel Play.
Verify that the steering wheel play is not excessive.
Inspection Procedure 2
Difficult Steering Wheel Operation /Insufficient Power Assist)
DIAGNOSIS
STEP 1. Check The Power Steering Belt Tension.
If not within the standard valve adjust the tension. Then go to Step 10.
If normal, go to Step 2.
STEP 2. Check The Belt For Damage.
If damaged, replace the belt. Then go to Step 10.
If normal, go to Step 3.
STEP 3. Check The Fluid Level.
1. Park the vehicle on a flat, level surface, start the engine, and then turn the steering wheel several times to raise the temperature of the fluid to approximately 50-60°C (122-140°F).
2. With the engine running, turn the wheel all the way to the left and right several times.
3. Check the fluid in the oil reservoir for foaming or milkiness. Check the difference of the fluid level when the engine is stopped, and while it is running. If the change of the fluid level is 5 mm (0.2 inch) or more, bleed air from the system
If fluid is foamy, go to Step 10.
If normal, go to Step 4.
STEP 4. Check For Entry Of Air.
If air has entered, bleed the air. Then go to Step 10.
If normal, go to Step 5.
STEP 5. Check Each Hose For Crushing Or Twisting.
If faulty, repair or replace the hose. Then go to Step 10.
If normal, go to Step 6.
STEP 6. Check For Oil Leaks.
If oil leaks are found, repair it. Then go to Step 10.
If normal, go to Step 7.
STEP 7. Check The Wheel Alignment (Camber And Caster).
If faulty, repair it. Then go to Step 10.
If normal, go to Step 8.
STEP 8. Check The Gear Box Rack Piston Seal For Damage.
If damaged, replace it. Then go to Step 10.
If normal, go to Step 9.
STEP 9. Check For Excessive Tie Rod End Ball Joint Breakaway Torque.
If faulty, replace the part. Then go to Step 10.
STEP 10. Check Steering Wheel Operation.
Verify that steering wheel operation is not difficult.
Inspection Procedure 3
Rattling Noise
DIAGNOSIS
STEP 1. Check For Proper Oil Pump And Gear Box Installation.
If incorrect, repair it. Then go to Step 4.
If correct, go to Step 2.
STEP 2. Check For Interference Of Other Parts With The Steering Column And Power Steering Hoses.
Correct the interference. Then go to Step 4.
If normal, go to Step 3.
STEP 3. Check For Noise From Inside The Oil Pump Or Gear Box.
If noise is heard, replace the part. Then go to Step 4.
STEP 4. Check For Rattling Noise.
Confirm that no noise is generated.
Inspection Procedure 4
Shrill Noise
DIAGNOSIS
STEP 1. Check For Entry Of Air.
If air has entered, bleed the air. Then go to Step 3.
If normal, go to Step 2.
STEP 2. Check For Seizure In The Oil Pump.
If seizure is found, replace the part. Then go to Step 3.
STEP 3. Check Symptoms.
Confirm that no noise is generated.
Inspection Procedure 5
Squealing Noise
DIAGNOSIS
STEP 1. Check The Belt For Slack.
If faulty, adjust the belt. Then go to Step 3.
If normal, go to Step 2.
STEP 2. Check For Seizure In The Oil Pump.
If seizure is found, replace the part. Then go to Step 3.
STEP 3. Check Symptoms.
Confirm that no noise is generated.
Inspection Procedure 6
Hissing Noise
DIAGNOSIS
STEP 1. Check For Entry Of Air.
If air has entered, bleed the air. Then go to Step 4.
If normal, go to Step 2.
STEP 2. Check Each Hose For Crushing Or Twisting.
If faulty, repair or replace the hose. Then go to Step 4.
If normal, go to Step 3.
STEP 3. Check The Steering Box For Damage.
If damaged, repair or replace the part.
Then go to Step 4.
STEP 4. Check Symptoms.
Confirm that no noise is generated.
Inspection Procedure 7
Droning Noise
DIAGNOSIS
STEP 1. Check The Oil Pump Or Oil Pump Bracket Installation.
If incorrect, repair it. Then go to Step 3.
If correct, go to Step 2.
STEP 2. Check The Oil Pump For Damage.
If a slight "beat noise" is produced by the oil pump when the steering wheel is turned fully and held in that position, this is not a malfunction.
If damaged, replace the oil pump. Then go to Step 3.
STEP 3. Check Symptoms.
Confirm that no noise is generated.
Inspection Procedure 8
Squeaking Noise
DIAGNOSIS
STEP 1. Check The Steering Stopper Contact.
If faulty, adjust it. Then go to Step 4.
If normal, go to Step 2.
STEP 2. Check For Interference Of The Wheel And Vehicle Body.
If interfering, adjust the steering angle.
1. Place the front wheel on a turning radius gauge and measure the steering angle.
Standard value:
2. If the steering angle is outside the standard value after checking the toe-in, adjust the steering angle with the stopper bolt. Then go to Step 4.
If normal, go to Step 3.
STEP 3. Check the steering gear box for damage. If damaged, repair or replace the part. Then go to Step 4.
STEP 4. Check Symptoms.
Confirm that no noise is generated.
Inspection Procedure 9
Vibration
NOTE: A slight vibration may be felt when the stationary steering effort is made due to the condition of the road surface. check whether the vibration actually exists or not, test-drive the vehicle on a dry concrete or asphalt surface. Moreover, a very slight amount of vibration is not a malfunction.
DIAGNOSIS
STEP 1. Check For Entry Of Air.
If air has entered, bleed the air. Then go to Step 3.
If normal, go to Step 2
STEP 2. Check The Steering Gear Box For Damage.
If damaged, repair or replace the part Then go to Step 3.
STEP 3. Check Symptoms.
Check that vibration is not generated
Inspection Procedure 10
Oil Leakage From Hose Connection
DIAGNOSIS
STEP 1. Check For Loosening Of The Flare Nut.
If loose, tighten it to 15 Nm (11 ft. lbs.). Then go to Step 3.
If normal, go to Step 2.
STEP 2. Check The Insertion Of The Hose And The Clamp Installation State.
If incorrect, repair or replace the part. Then go to Step 3.
STEP 3. Check Symptoms.
Check that no oil is leaking.
Inspection Procedure 11
Oil Leakage From Hose Assembly
DIAGNOSIS
STEP 1. Check The Hose For Damage Or Clogging.
If damaged or clogged, repair or replace the hose Then go to Step 2.
STEP 2. Check Symptoms.
Check that no oil is leaking.
Inspection Procedure 12
Oil Leakage From Oil Reservoir
DIAGNOSIS
STEP 1. Check The Oil Reservoir For Damage.
If damaged, repair or replace it. Then go to Step 3.
If normal, go to Step 2.
STEP 2. Check For Overflowing.
If overflowing, adjust. Then go to Step 3.
STEP 3. Check Symptoms.
Check that no oil is leaking.
Inspection Procedure 13
Oil Leakage From Oil Pump
DIAGNOSIS
STEP 1. Check The Oil Pump Body For Damage.
If damaged, replace the part. Then go to Step 3.
If normal, no to step 2.
STEP 2. Check The O-ring Or Oil Seal For Damage.
If damaged, replace the part. Then go to Step 3.
STEP 3. Check Symptoms.
Check that no oil is leaking.
Inspection Procedure 14
Oil Leakage From Gear Box
DIAGNOSIS
STEP 1. Check The Gear Box Housing For Damage.
If damaged, replace the part. Then go to Step 3.
If normal, go to Step 2.
STEP 2. Check The Oil-Ring Or Oil Seal For Damage.
If damaged, replace the part. Then go to Step 3.
STEP 3. Check Symptoms.
Check that no oil is leaking.