Removal of air from a hydraulic drive of the amplifier of a steering mechanism

The presence of air in the hydraulic system leads to failure of the power steering. Air can enter the hydraulic system if it has been opened, or if, as a result of a leak, the liquid level in the compensation tank has dropped so much that the oil pump begins to suck in air.

When replenishing or filling the hydraulic system, use only automatic transmission fluid (AND THOSE), compliant with FORD specification ESPM-2C-166H

Caution: Do not shake automatic transmission fluid. because this leads to the formation of air bubbles in it.

Note: The drawings do not apply to FORD SCORPIO vehicles.

Air removal

Fill the expansion tank up to the MAX COLD mark with new, clean transmission fluid without air bubbles.

Attention: To avoid the formation of air bubbles, pour the transmission fluid slowly.

Start the engine and leave it to idle. Turn the steering wheel 3-4 times slowly to the left and to the right from lock to lock.

Ask an assistant to observe the fluid level in the expansion tank. The liquid level must not fall below the MIN·mark and must be topped up if necessary.

Repeat the process until the release of air bubbles in the compensation tank stops.


Check the tightness of the hydraulic system. Inspect for oil loss through pipe connections, gear rack collars and valve body.

Switch off the engine, check again and, if necessary, top up the fluid level in the expansion tank.

Note: while the car has not started off, slight noise is possible from the hydraulic booster with the engine running after bleeding.

In case of strong noise disturbances, bleed the hydraulic system using a manual vacuum pump.



At the service station, instead of a cover, an adapter -1- with a vacuum hose is installed on the compensation tank. A suitable adapter can be made independently from a spare cover.

Connect the vacuum pump.

Start the engine and slowly turn the steering wheel to the right almost to the stop.

Shut off the engine and use the vacuum pump to create a vacuum of 0.5 bar until the air is completely out of the system.

Attention: Maintain vacuum for at least five minutes. If the vacuum drops, restore it with a vacuum pump.

Finally, release the vacuum. Slowly turn the steering almost all the way to the left and repeat the bleeding operations.


Remove the vacuum pump, check and, if necessary, replenish the liquid level in the expansion tank. Screw on the cover of the expansion tank.

Start the engine and turn the steering wheel from lock to lock. In case of increased noise interference, repeat the venting operations.

If the noise level is still high, leave the vehicle overnight and repeat the bleed operations the next day.