Pressure Reduction Stage - Fiat 1998 Marea Service Manual

Braking system
Anti-lock brakes
33.

Pressure reduction stage

pressure increase
MWMXI
i i pressure decrease
3
E C U
1. Electronic control unit
2. Low pressure accumulator (reservoir)
3. Recovery pump motor
4. Recovery pump
5. Restricter
6. Brake pump
7. Brake servo
The electronic control unit (1) detects the tendency of the wheel to lock and alerts the electro-hydraulic
unit to contain the deceleration of the wheel within the permissible limits.
The electronic control unit (1) connects the pressurizing (9) and discharging (10) solenoid valves to
earth.
The pressurizing solenoid valve (9) remains closed keeping the connection between the brake pump (6)
and the brake caliper (11) interrupted; the discharging solenoid valve (10) opens making a hydraulic
connection between the brake caliper (11) and the low pressure accumulator (2) and the recovery
pump (4), in such a way as to remove some of the fluid from the brake caliper (11) and decrease the
pressure at the actual caliper.
At the same time, the electronic control unit (1) supplies the recover pump (4) motor (3) which allows
the fluid removed from the brake caliper (11) to be reintroduced into the main circuit.
The low pressure reservoir or accumulator (2) in the circuit has the task of storing part of the brake fluid
removed from the calipers. The fluid is drawn in through the recovery pump (4) circuit and sent, by
means of the restricter (5), into the brake pump (6) main circuit.
During this stage a series of pressure waves (or hydraulic thrusts) are produced which notify the driver
that the ABS device has started to work.
During braking, slight force on the brake pedal should be considered normal during the intervention of
the A.B.S. system. During this stage, as a result of the decreased braking force, the wheel tends to return
to the reference speed calculated by the electronic control unit (1).
12
+12V
1 0
Marea - Marea Weekend
+12V
tin
8. Multi-polar ring
9. Pressurizing solenoid valve
10. Discharging solenoid valve
11. Brake caliper
12. Rpm sensor
13. Single-acting valve
Print no. 506.763/10