POWER-STEERING

POWER-STEERING SYSTEMS

The power-steering unit is designed to reduce the amount of effort required to turn the steering wheel. It also reduces driver fatigue on long drives and makes it easier to steer the vehicle at slow road speeds, particularly during parking. Power steering can be broken down into two design arrangements: conventional and non conventional or electronically controlled. In the conventional arrangement, hydraulic power is used to assist the driver. In the non- conventional arrangement an electric motor and electronic controls provide power assistance in steering. There are several power-steering systems in use on passenger cars and light-duty trucks. The most common ones are the external-piston linkage, integral-piston, and power-assisted rack and pinion system

EXTERNAL- PISTON LINKAGE SYSTEM

The external-piston linkage system, sometimes called non integral, is generally found on older cars. It consists of a power-steering pump and resenroi control valve, power cylinder and four hoses. The control valve and pressure cylinders are separate components that are not incorporated into the steering gear. The pressure hose connects the pump to the control valve and directs the pressurized fluid into the correct booster hoses to the power cylinder. The power cylinder piston provides the necessary power assistance.

INTEGRAL PISTON SYSTEM

The integral piston system is one of the most common conventional power-steering systems in use today. It consists of a power-steering pump and reservoir, power-steering pressure and return hose, and steering gear. The power cylinder and the control valve are in the same housing as the steering gear. On some recent model cars and light trucks, instead of the conventional vacuum-assist brake boosted the hydraulic fluid from the power-steering pump is also used to actuate the brake booster. This brake system is called the hydro-boost system. Major advantage of this system is that it reduces the drivers efforts needed in turning the steering wheel by utilising the hydraulic pressure generated by the power steering (P/S) pump which is driven by the engine. Information on Power Steering system and points to be checked during PDI/FREE SERVICE/ PAID SERVICES are given in the annexure.

INSPECTION POWER STEERING FLUID LEVEL

With engine stopped, check fluid level indicated on oil tank, which should be between "UPPER" and "LOWER" marks. lf it is lower than "LOWER" mark, fill fluid up to “UPPER” mark.

NOTE : Be sure to use an specified power steering fluid. Fluid level should be checked when fluid is cool.

POWER STEERING BELT TENSION

Check that belt free from any damage and porperly fitted in pulley groove. Check belt tension by measuring ,how much it deflectes when pushed at intermediate point between P/s pump pulley and crank pulley with about 10 kg (22 lb) force.
Deflection of P/S belt (A) 8- 10mm

POWER STEERING BELT TENSION ADJUSTMENT

1. Remove splash cover and loosen tension nut.

2. Adjust belt tension. With A/C equipped vehicles, turning tension bolt counter clockwise causes pulley to rise, and increasing belt tension. With A/C non equipped vehicle, turning tension bolt clockwise causes pulley to lower, increasing belt tension. In both cases, truning tension bolt in the other way decreases belt tension. Be sure to tighten tension nut after adjusting belt tension.
Tightening torque - 450 kg-cm

IDLE UP SYSTEM

This system operates when a power steering assist load is applied to the engine open the throttle valve a little so that the engine idle speed is stabilished.

OPERATION

When the power steering starts steering assist function, the hydraulic pres-sure in the Power steering pump rises. This pressure rise causes the. Pressure switch in the P/s pump to close to transmit a signal to the p/s idle up relay which then turns ON. As a result a voltage is applied to the idle up VSV to actuate it to open vacuum passage, Vacuum from the intake manifold pulls up the diaphragm of idle up actuator .According to the diaphragm movement, the idle up rod and idle up lever move and push down the throttle lever a little further than the ordinary idle speed position. This opens the throttle valve by the same angle as the throttle level movement resulting in idle up function. Resulting in idle up function. The idle up engine speed is adjusted by turning the idle up adjusting screw.

FLUID LEAKAGE

Start engine and turn steering wheel fully to the right and left so that maximum hydraulic pressure is provided. Then visually check gear box. P/S. pump and oil tank themselves and each joint of their connecting pipes for leakage.

CAUTION: Never keep steering wheel turned fully for longer than 10 Seconds.
POWER STEERING IDLE UP CHECKING AND ADJUSTMENT PROCEDURE

1.WARM UP ENGINE TO NORMAL OPERATING TEMPERATURE.

2. TURN A.C. SWITCH OFF

3. TURN STEERING WHEEL FULLY AND HOLD IT THERE LIGHTLY

4. CHECK IDLE RPM

ENGINE IDLE RPM SHOULD DROP BY 50 To 1OO RPM MOMENTARILY AND RETURN BACK TO SPECIFIED IDLE RPM IMMEDIATELY. IDLE UP RPM SHOULD BE ADJUSTED KEEPING THE STEERING WHEEL AT FULLY TURNED POSITION.
DIAGNOSIS

Condition: Steering wheel feels heavy (at low speed)

Possible Cause: 1. Fluid deteriorated, low viscosity different type of fluid mixed.

Correction: Replace fluid

Possible Cause: 2. Pipes or hoses deformed, air entering through joint .

Correction: Replace defective port.

Possible Cause: 3. insufficient air purging from P/S circuit.

Correction: Purge air.

Possible Cause: 4. P/S belt worn, lacking in tension.

Correction: Adjust belt tension or replace belt as necessary

Possible Cause: 5. Tire inflation pressure excessively low.

Correction: inflate tire

Possible Cause: 6. Front end alignment maladjusted.

Correction: Check and adjust front end alignment

Possible Cause: 7. Steering wheel installed improperly (twisted)

Correction: Install steering wheel correctly.

Possible Cause: 8. Bind in tie rod or tie rod end ball joint.

Correction: replace defective part.

Possible Cause: 9. P/S pump hydraulic pressure fails to increase.

Correction: Replace P/S pump.

Possible Cause: 10. P/S pump hydraulic pressure increases but slowly

Correction: Replace P/S pump.

NOTE: Make sure to warm up engine fully before measuring hydraulic pressure from pump.

Condition: Steering wheel feels heavy momentarily when turning it to the left (right)

Possible Cause:

1.Air drawn in due to insufficient amount of fluid

2. Slipping P/S belt Adjust belt tension or replace belt as necessary.

3. Refer to check items 9 and 10 ink above section

Correction: Add fluid and purge air.

Condition: No idle-up

Possible Cause: P/S pump pressure switch defective

Correction: Replace P/S pump pressure switch.

Condition: Poor recovery from turns

Note: To check steering wheel for recovery, with 22 mile/h (35 km/h) vehicle speed, turn it 90 degree and let it free. It should return more than 60 degree.

Possible Cause: 1. Deformed pipes or hoses.

Correction: Replace defective part.

Possible Cause: 2. Steering column installed improperly.

Correction: install steering column correctly.

Possible Cause: 3. Front end alignment maladjusted.

Correction: Check and adjust front end alignment

Possible Cause: 4. Ball joints binding Replace defective part

Condition: Vehicle pulls to one pressure side during straight driving

Possible Cause: 1. Low or uneven tire inflation pressure.

Correction: inflate tires to proper or adjust right & left tires inflation pressure.

Possible Cause: 2. Front end alignment maladjusted

Correction: Check and adjust front end alignment.

Possible Cause: 3. Malfunction of control valve in gear box.

Correction: Replace gear box.

Condition: steering wheel play is large and vehicle wanders

Possible Cause: 1. Loose steering shaft nut

Correction: Re-tighten.

Possible Cause: 2. Loose linkage or joints

Correction: Re-tighten.

Possible Cause: 3. Loose gear box fastening bolt

Correction: Re-tighten.

Possible Cause: 4. Front wheel bearing worn

Correction: Replace wheel bearing.

Condition: Oil leakage

Possible Cause: 1. Loose joints of (hydraulic pressure) pipes and hoses

Correction: Re-tighten.

Possible Cause: 2. Deformed or damaged pipes or hoses

Correction: Replace defective part.

NOTE: sound may be heard through steering column when turning wheel with vehicle at a stop but it is not an abnormal noise but operating sound of valve in gear box.

Possible Cause: Air drawn in due to insufficient amount of fluid

Correction: Add fluid and purge air.

Possible Cause: Air mixed into fluid from pipes or hoses.

Correction: Replace pipes or hoses

Possible Cause: Slipping (loose) P/S belt

Correction: Adjust belt tension.

Possible Cause: Worn P/S belt Replace belt.

Correction: Re-tighten bolt.

Possible Cause: Loose gear box fastening bolt

Correction: Re-tighten bolts.

Possible Cause: Loose pitman arm nut

Correction: Re-tighten.

Possible Cause: Loose linkage or joints

Correction: Re-tighten.

Possible Cause: Pipes or hoses in contact with part of vehicle body

Correction: Install pipes and hoses correctly.

Possible Cause: Vanes of P/S pump defective

Correction: Replace pump.

Possible Cause: Malfunction of control valve in gear box.

Correction: Replace gear box.

Possible Cause: Bearing of P/S pump shaft defective

Correction: Replace pump.