brake fluid DACIA SUPERNOVA 2004 User Guide

31
FRONT BEARING ELEMENTS
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BRAKE CALIPER
REMOUNTING
Perform the dismounting operations in the reverse order plus the following operations : - fill the caliper with brake fluid in order to facilitate the brake system purging;
- purging the brake system.
BRAKE CALIPER SEALING CHECKING
Connect to the caliper, a pressure gauge attached to a compressed air source.
P lace a wooden wedge in order to block the piston.
Create a 0,3 bars pressure in the caliper.
Dip the caliper into a vessel with alcohol.
Move the piston several times to remove the air from the sealing gasket seat.
Check the sealing of the brake caliper at various pressu res, without exceeding the pressure of 2 bars.
If the brake shows air leaks by the piston, perform at its dismounting.
Replace the piston, the ga sket, or the caliper body, as the c ase stands.
Perform again the sealing test.
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REAR BEARING ELEMENTS
REAR AXLE
Check and adjust the hand brake cable.
Ad just the cleara nce at t he l imi ter ope rating rod (se e chapt er 37- Bra ke l imite r
adjustment). REMOUNTING
Before remounting, grease with grease the attachment screws of the rear axle shock
absorber bottom and the chassis, consequently, the connecting screws rear a xle-c hassis. Line up the arm s beari ngs right to t he c hassis supports, mounting them without t ighten-
ing at the moment, the nuts with the screws, assembling the axle to the chassis.
Remount the springs.
Compress the axle so that rear springs bear on the tray and set back the shock absorber
inner attachment screws. Tighten at the prescribed moment the connecting screws.
Perform the dismounting operations in the reverse order.
Check the maximum allowed axial cleara nce of the bearing using a dial gauge and the
s upport RO541A.
Note
The maximum allowed axle clearance of the bearing is 0.05mm.
Mount the rear wheels, lower t he vehicle on the ground.
Refill with fluid the brake assembly.
Pu rge the braking system.
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REAR BEARING ELEMENTS
BRAKE CYLINDER
A djust:
- the shoes, by applying a repeated pressure to the brake pedal;
- the rear axle bearing clearance.
Mount the wheel.
Lower the vehicle from the elevator.
Pu rge the braking system (see chapter 38).
Adjust the hand bra ke.
REPAIRING
DISMOUNTING
Di smount the bra ke cylinder off the vehicle;
Di smount:
- the purging screw;
- the protection bellows;
- the Ö22 pistons assembled with the pressure ga skets.
Check the condition of the cylinder boring, any trace of wear, oxidation or scratches
implies the re placement of the assembled bra ke cylinder.
If the cylinder components are in a good condition, lubri cate them with brake fluid and
mount them in the reverse order of dismounting. Check the easy moving of the assembled pistons in the cylinder boring.
Mount the brake cylinder on the plate;
Mount the wheel brake drum .
Check the adjustment of t he hand bra ke.
Purge the braking system.
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MECHAN ICAL ELEMENTS CONTROL
37
BRAKE PUMP
BRAKE PUMP WITH PRESSURE DROP INDICATOR ( ICP ) INCLUDED
COMPONENTS
1. Assembled primary piston with gaskets
2. Assembled secondary piston with gaskets
3. Primary piston pin.
4. Secondary piston pin.
5. Primary piston return spring
6. Secondary piston return spring.
7. Purging screw
8. ICP transducer
A –A ICP assembly section
OPERATIONA. B RAKING
THE FRONT BRAKE CIRCUIT
The primary piston is controlled by the pushing rod. A part of the brake fluid under pressur e
will operate together with the spring on the secondary piston, and the other part of the brake flui d
shall penetrate through the ducts to the upper floor towards both exits leading to the front brak e
calipers.
THE REAR BRAKE CIRCUIT
The secondary piston is continuing its movement, conducting the brake fluid under pressure ,
through the ducts, to the upper floor, towards the exit to the pressure-reducing valve. During al l
this time, the linings-pistons assembly will be balanced due to the two side springs .
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MECHAN ICAL ELEMENTS CONTROL
37
B. DE-BRAKING
After effort ending, the two pistons resume their initial position under the effect of the retainer
springs, while the fluid is coming back and the pressure is decreasing in both circuits.
PRIMARY CIRCUIT – PRESSURE LOOSING
Lack of pressure in the primary circuit leads to the following situation :
The primary piston is a dvancing up to the pin, so is controlling mechanically the secondary
piston. The secondary piston reaches a fluid pressure that shall operate on the piston – linings
assembly moving it t o the right, opening also t he second e xit of t he rear circ uit ( the by-pass
circuit) increasing the pressure for this circuit. In this moment, by means of the transducer, the warning light on the instrument panel is on.
SECONDARY CIRCUIT – PRESSURE LOOSING
Both pump pistons go on. The caliper cylinders of the front brake shall normally operate.
The secondary piston re aches its respective pi n, but the pre ssure will decrease (due to the
failure). BRAKE PUMP
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MECHAN ICAL ELEMENTS CONTROL
37
BRAKE PUMP
Close the connection pipe between the brake fluid reservoir and clutch transmitter cylinder
by means of the MOT 453 device. Disconnect the battery.
Drain the brake fluid reservoir.
Disconnect the connection pipe between the brake fluid reservoir and clutch transmitter
cylinder.
Dismount the brake fluid reservoir off the brake pump (avoiding fluid leakage).
Dismou nt :
- the rigid pipe screws from the brake pump and mark their position;
- the two attachment nuts of the brake pump on the servobrake .
DISMOUNTING
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TIGHTENING MOMENTS (daNm)
Rigid pipe connection 1,5
Nut attachment P.C. with servobrake 1,3
I.C.P. (pressure drop indicator) 2
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MECHAN ICAL ELEMENTS CONTROL
37
BRAKE PUMP
REMOUNTING
Perform the dismounting operations in reverse order.
Check the length of the pushing rod , value X = 9 mm and correct if necessary.
Before remounting, check the servobrake pushing rod stroke ( min.30 mm ).
After assemblin g the brake with the fluid reservoir and filling with brake fluid, no leakage must
occur in the surface of separation between the two elements.
IMPORTANT
The I.C.P. transducer is mounted after t he braking system purging.
ICP sub-assembly is not reparable ( ICP – pressure-decreasing indicator)
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MECHAN ICAL ELEMENTS CONTROL
37
BRAKE PUMP REPAIRING
The operation is performed after dismounting the central pump off the vehicle.
DISMOUNTING
Dismount the brake fluid reservoir, recover-
ing the two sealing gaskets of the brake fluid res-
ervoir. Dismount the transducer and the purging
screw. Clamp a 3,5 mm drill in the vice.
Introduce the drill in the elastic pin
Rotate and draw the pump until the pin is ex-
tracted;
Extract the secondary piston elastic pin, in the
same way. Remove from the pump:
-the Pp primary piston assembled ;
- the primary piston return spring;
- the Ps secondary piston assembled;
- the secondary piston return spring
Wa sh the part s with alcohol and bl ow them
with compressed air. Check:
-the pump bore
- the pistons gaskets
- the springs
The parts of the “ primary piston” Pp and those of the “ secondary piston” Ps, cannot be repaired.
In case one of these parts is damaged, replace the whole kit ” primary piston” and “secondary
piston”, primary piston return spring, secondary piston return spring.
REMOUNTING
Before remounting, the parts and the pump bore will be lubricated with brake fluid.
Mount the “ secondary piston” and “primary piston “ assembly .
Compress the pistons and introduce the elastic pins; the pins slot shall be oriented towards the
pump attachmen t flange.
Mount the purging screw;
P urge the brake circuit and remount the ICP transducer. BRAKE PUMP
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MECHAN ICAL ELEMENTS CONTROL
37
MASTER VAC 7 SERVO M ECHANISM
The ” Master-Vac 7” servobrake is a brake booster with the objective of reducing the driver
effort on the brake pedal.
AT TENT ION
The servobrake cannot be repaired.
The only items of the servobrake which are to be replaced are the air filter and the retainer
valve.
DISMOUNTING
Close the pipe between the brake fluid reservoir and the clutch transmitter cylinder by means
of the MOT 453 device.
Drain the liquid out of the reservoir.
Disconnect from the reservoir the feeding pipe of the clutch transmitter cylinder. SERVOBRAKE
OBSERVAT ION
In case one circuit is damaged, the pedal stroke shall be longer, the braking being
done only by the circuit still working.
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T I GHTENING MOME NTS (daNm)
Brake pump nut on servobrake 1,3
Servobrake attachment nut on the cowl panel 2,0
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MECHAN ICAL ELEMENTS CONTROL
37
BRAKE PRESSURE CONTROLLER
Brake pressure controller, load sensitive, avoiding the rear wheels blocking.
OPERATION PRINCIPLE
The brake pressure controller enables the rear circuit pressure “ modulation “ according to
two parameters:
-the pressure value in the front circuit
- the load on the rear axle
The pressure controller is operating on the principle of pressure compensation in two enclosures,
separated by means of a ball and spring valve. The back pressure at the valve level is created by means of the forc e developed by the
continuos action compensating spring and of the control spring acting in proportion as the rear
axle load is increasing. The pushing rod is transmitting the force of the lever spring to the pressure controller piston,
which is controlling the valve ball being in the open normal position (position P 1).
BRAKING MOMENT
In the same time with pressure increase when entering in the pressure controller, this will act
upon the ball, forcing it to overcome the c ontinuos acting spring force and by uncovering the
valve hole, to facilitate the releasing of this pressure. In the braking moment, due to position
changing of the vehicle body compared to the rear axle, by means of the acting levers, the limiting
piston is moving toward the interior, reducing the fluid exist diameter, leading to the obtaining in
this way of the pressure reduction in the rear circuit.
DE BRAKING MOMENT
In the moment of fluid inlet pressure restoring ( by leg lifting from the brake pedal ), the piston
will come back in the initial position, gradually and quickly allowing the same diameter existent at
the beginning of the braking for which the valve is open ( position P1 ). 1.
Pressure controller body
2. Valve
3. Plug
4. Spring
5. Ball
6. Piston
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