The power steering pump (Fig. 1) is a double-acting vane type, i.e., for one revolution of the pump rotor, two complete suction and two discharge cycles are performed

In the pump rotor there are vases in which the blades are placed. The blades should move freely in the vases, without jamming.

In the suction cavities, oil enters the space between the vanes, and then is forced out into the discharge cavity.

Oil is displaced as a result of the reduction in volume between the vanes as the rotor rotates inside the stator, which has a special profile.

GAZ-66 power steering

An oil reservoir is installed on the pump. There is a filler filter under the tank cover, and a strainer is installed on the drain hose through which oil returns from the system to the pump.

Two valves are placed in the pump cover. The safety valve (internal) limits the maximum pressure in the system within 65-70 kg/cm2.

The bypass valve limits the amount of oil that is supplied by the pump to the power steering system at increased engine speeds.

The valve is designed in such a way that no more than 10 l / min of oil is sent to the hydraulic booster system.

Excess oil is bypassed inside the pump and goes back to the suction cavity.

The control valve is located at the front end of the tie rod.

Inside the valve body there is a spool, which is connected through intermediate parts to the steering arm pin.

The spool is sealed with rubber cuffs at both ends.

When the spool is in the middle position (the car is moving straight), the oil flowing through the discharge hose to the control valve is bypassed through the gaps between the ends of the spool necks and the channels in the housing into the drain hose and returns to the pump reservoir.

When the steering wheel is turned, the bipod finger moves the spool, which, blocking the channels in the valve body, directs oil under pressure into one or another cavity of the power cylinder (depending on which direction the turn is made).

The rod of the power cylinder, connected to the tie rod, moves it, turning the front wheels.

After the rotation is completed, the spool is set to the middle position, the oil pressure in the power cylinder decreases, and the oil from the valve returns back to the pump without entering the power cylinder.

A double-acting power cylinder is mounted in a bracket on the front axle housing through a ball joint.

The rod piston is sealed with two elastic cast iron rings.

The cylinder rod is chrome-plated for increased wear resistance and corrosion protection.

The rod exit from the cylinder is sealed with a rubber cuff. To protect against dirt ingress, brass washers and a felt gland are installed on the outside. The power cylinder, in addition to turning the front wheels, also absorbs shocks from the wheels when moving through various bumps.

This greatly relieves the steering gear and other steering parts from shock loads.

Hydraulic booster maintenance

The power steering pump drive belts are tensioned by tilting the pump housing. The angle of inclination of the pump housing should not be too large and should allow the oil to be filled into the pump reservoir.

If the tension of the belts is not ensured by tilting the pump housing, rearrange the pump on the holes in the bracket, and with a large stretch of the belts, rearrange the pump brackets to additional holes in them.

With normal belt tension, the deflection of each belt between the pulleys of the compressor and the hydraulic booster pump should be 15-20 mm when the belt is pressed with a force of 4 kg.

When checking the oil level in the power steering reservoir, the front wheels of the car must be installed straight.

Add oil while the engine is idling up to the “oil level” mark on the wall of the pump reservoir or, if there is no mark, to the filler filter screen.

Before removing the reservoir cap to check the level, top up or change the oil, it must be thoroughly cleaned of dirt and washed with gasoline.

Pour oil through a funnel with a double mesh and a filling filter installed in the pump reservoir.

In case of significant clogging of the filters with resinous deposits, additionally wash the filters with solvent No. 646 used when painting the car.

During operation, regularly check the tightening of the bolts for fastening the pump and its brackets and the bolts for fastening the control valve to the longitudinal link.

Regularly check the tightness of the ball stud nut securing the power cylinder to the bracket. Loosening this nut loosens the ball pin in the tapered hole of the bracket.

Check periodically the tightening of the power cylinder rod nut and the condition of the rubber cushions through which the rod is attached to the thrust bracket. If the rubber pads are worn out, they must be replaced.

Oil change

To change the oil, lift the front wheels of the car and open the power steering pump reservoir cap.

To drain the oil you need:

  • - disconnect the discharge and drain hoses from the control valve body and drain the oil from the pump through them;
  • - disconnect the hoses from the fittings of the power cylinder; and drain the oil from the control valve;

Drain the oil from the power cylinder by slowly turning the steering wheel to the right and left until it stops.

After draining the oil, flush the power steering system with fresh oil. Filter meshes are washed separately.

To pour fresh oil you need:

  • - connect all hoses;
  • - pour fresh oil into the tank up to the “oil level” mark and pump the oil at a low number of revolutions of the engine crankshaft by turning the steering wheel 2-3 times to the stop in both directions without delay in the extreme positions .

When pumping oil, monitor its level in the reservoir and add oil if necessary. The total capacity of the power steering system is about 1.8 liters of oil;

  • - install the reservoir lid with a sealing gasket, the rubber ring of the lid fastening stud and the washer and secure with a wing nut.

Tighten the wing nut only by hand. In case of oil leakage from under the cover, change the cover gasket.

Driving a car with the hydraulic booster not working

The steering of the car allows you to continue driving with a faulty hydraulic booster. In this case, it should be borne in mind that the effort to turn the car on the steering wheel will increase.

To continue driving with a faulty hydraulic booster, turn off the pump by removing the drive belts.

To reduce the force on the steering wheel, if the hydraulic booster is damaged, drain the oil from the hydraulic booster system.

In case of damage or malfunction of the power cylinder, remove it.

Prolonged driving with a faulty power steering is not recommended.

Check steering wheel free play. The free play of the steering wheel is determined by the adjustment of the steering gear engagement and the design features of the hydraulic booster.

When the hydraulic booster is not working, the free play of the steering wheel is greater than when it is working. This is a design feature of the hydraulic booster.

The maximum allowable free play of the steering wheel with the power steering on is 60 mm around the circumference of the steering wheel (or 15°), with the power steering off 120 mm (or 30°).

Checking the pressure developed by the hydraulic booster pump

To make sure that the power steering pump is working properly, it is necessary to measure the oil pressure generated by the pump.

To do this, unscrew the discharge hose from the threaded hole of the pump and screw an adapter with a pressure gauge and a tap into this hole.

The pressure gauge must have a scale of at least 80 kg/cm2. On the other hand, screw the discharge hose into the adapter.

To check, you need to open the tap and turn the front wheels of a stationary car all the way to the right or left.

In the extreme positions of the wheels, the oil pressure must be at least 60 kg / cm2 , at idle speed of the engine crankshaft.

If the oil pressure is less than 60 kg/cm2, then you need to close the valve on the adapter and monitor the oil pressure on the pressure gauge.

With a working pump, the pressure should rise and be at least 60 kg/cm2.

If the pump fails, the pressure will not increase. If the pressure increases to 60 Kg / cm2, then the fault must be sought in the control valve or power cylinder.

When checking, do not keep the valve closed or the car wheels in extreme positions for more than 15 seconds, as this can lead to overheating and scuffing of the pump parts.

The oil in the pump reservoir should be warm when checking.

Power steering malfunctions and solutions

- Causes of malfunction


Insufficient or uneven power steering when turning the steering wheel in both directions:

- Insufficient tension of the pump drive belts

Tighten the straps

- Insufficient oil level in the pump reservoir

Add oil

- The presence of air or water in the system (foam in the tank, cloudy oil)

Remove air. If the air is not removed, check the tightness of all connections, remove and rinse the strainer, check the integrity of the gasket under the manifold and the tightening of its fastening bolts. Change oil if necessary

- Pump failure

Check pump

- Stuck control valve spool

Disassemble and flush the control valve

- Seizure of the rod or piston of the power cylinder

Find out the cause and location of the jam. Repair or replace damaged parts

-Increased oil flow through the sealing rings in the power cylinder due to their wear or breakage

Disassemble the cylinder and replace the rings

- Periodic freezing of the pump bypass valve due to contamination

Disassemble the pump, check the free movement of the valve

No boost when turning the steering wheel to the right:

- The control valve spool bolt has loosened

Tighten bolt

Complete lack of amplification at various engine speeds:

- Unscrewing the pump safety valve seat

Disassemble the pump, wrap the seat

- Pump bypass valve sticking

Disassemble the pump, clean and rinse from dirt.

If heavily soiled, flush the entire power steering system

Increased noise during pump operation:

- Insufficient oil level in the pump reservoir

Add oil

- Insufficient tension of the pump drive belts

Tighten the straps

- Clogged or incorrectly installed filter

Rinse the filter, put it right

- Presence of air in the system

Remove air

- deformation of the collector plane in the pump reservoir

Repair or replace manifold

- Strong wear and scuffing of pump parts

Disassemble and check pump parts, replace if necessary

Rattle at the front of the pump:

- Strong wear of the ball bearing of the pump shaft

Replace bearing

Ejecting oil through the breather:

- Oil level above mark

Set normal level

- Strainer clogged

Rinse filter

- Damaged manifold gasket

Replace gasket

- Bent manifold

Repair or replace manifold