Fiat Bravo Service Manual page 493

Steering
Power-assisted steering
Bravo-Brava
41.
Power steering distributor valve
The power steering pump is driven by the engine by a belt, and
can supply a feed pressure varying from 3.5 bar in the "neutral"
position to a maximum of 85 bar in the "full lock" position.
The power-assisted steering assembly is similar to a mechanical
steering gear, except for the following differences:
a. the steering gear contains an actuating cylinder (2) in which a
double-effect piston (1) slides, joined to the rack;
b. in the seating of the worm screw, there is a distributor valve
(3) with its pipes. It is controlled by a torsion device (4), lo­
cated at the end of the worm screw.
Depending on the torsion transmitted by the steering wheel to
the device, the fluid is sent from the pump to the reservoir, or to
one of the two chambers A or B of the actuating cylinder.
The force generated by the fluid pressure on the lateral surface of
the piston causes the piston, and hence the rack, to move.
Longitudinal section of power-assisted rack and pinion steering gear
Checking operation
Check the steering wheel's rolling torque with the car stopped and the engine running. The torque
should be between 0.6 daN with the engine idling and 0.75 daN with the engine at maximum rpm. If it
exceeds these values, check the system pressure with the wheels at full lock. To do this, fit a pressure
gauge, with a T connector, on the pressurized fluid delivery pipe to the power steering gear (from the
pump) and turn the steering wheel to full lock on one side. When the steering wheel is forced to rotate
further, the pressure reading on the pressure gauge should rise to about 85 bar. If this does not happen,
check whether there is a fault in the power steering fluid pump or distributor valve.
The above check should be conducted with the engine running at 2000 - 4000 rpm.
NOTE Under no circumstances should the power steering assembly and vane pump be dismantled in­
to their components; instead they should be returned to the manufacturer for overhaul.
Checking fluid level: the fluid level should be checked with the engine running, and it should be topped
up as necessary.
10 Publication no. 506.670