Dacia Pick-Up 1304/1305/1307. Service manual - part 66

GENERAL

30

       AIR ELIMINATION FROM THE HYDRAULIC CIRCUIT ( PURGING )

  The air existence in the hydraulic circuit may be noticed by an elastic displacement of the
brake pedal, sometimes even, close to the floor. This fact is more evident with the engine
stopped.

G

ENERAL

  

RECO MMENDATIONS

Always use for completion or total changing the brake fluid Norm  SAE J 1703, DOT 4.
In case of changing the brake fluid it is necessary to wash the system with one liter of

industrial alcohol.

During the purging, the brake fluid from the tank must not go down bellow the

 minimal level marked on the tank.
     To perform the purging, one person will stay on the driver place, to push the brake

pedal and the other one will perform the purging (bleeding) at the wheel using a 500 ml
vessel, a transparent plastic tube and brake fluid for completion.

P

RO CEDURE

    Place on the bleeding (purging )screw, a transparent tube with its end in a vessel with
brake fluid and proceed as follows:press the brake pedal slowly, dismount the bleeding
screw, maintaining the full stroke of the pedal, then tighten the bleeding screw and slowly
release the brake pedal.
    Repeat the same procedure until complete cease of bubbles. Proceed in the same way
also for the other purging places.( Take into consideration the existence all the time of the
brake fluid in the tank ).

ATTENTION  : Before beginning the purging  procedure dismount the I.C.P. from

the brake pump. It shall be remounted at the end of the operation.

P

RO CEDURE

 

IN

 

PARALLEL

 

SYSTEM

It is important to observe the following sequence of the purging points:

1,6

.  Main cylinder with I.C.P. incorporated;

   2

. Left rear wheel brake cylinder;

   3

. Right rear wheel brake cylinder;

   4

. Caliper of front right wheel;

   5

. Caliper of front left wheel.

                                        O

PERATING

 

CO NDITIONS

    The vehicle is on wheels.
    If the fuel tank is empty, place on the rear bench of the vehicle one or two persons to
enable the possibility of the circuit opening ( the passing of a larger fluid flow through the
brake limiter).

C

H ECKING

 

TH E

 

BRAK E

 

SYSTEM

 

SEALING

After purging the front and rear circuits, check if the level of brake fluid in tank is

within the prescribed limits, than press the brake pedal for 30 s ,during this time the pedal
shall not change its place.

Leaking in the brake system is not acceptable.

BRAKING CIRCUIT PURGING

30 - 10

GENERAL

30

DIAGNOSTIC

30 - 11

    Rigid pedal: when braking, an
increased effort for a  small decel-
eration is performed

Yes

 Replace: shaft,  pedal or

servobrake fork.

Yes

Yes

Yes

No

No

No

No

 Replace the servobrake

(broken membrane)

 Replace the servobrake

(broken membrane)

 Check:
- the integrity of the depression
pipe, consequently of the  retain-
ing valve;
- the sealing of the depression pipe
at the servobrake, consequently at the
vacuum pump (inlet manifold).

 Is the engine

regime changing

when braking ?

The engine
pedal is rigid
from time to
time ?

1

Is the connection
shaft between the
servobrake fork
and the pedal,
     grabed?

At the servobrake
entrance is the
depression the
imposed one ?

I.     FAILURE : RIGID PEDAL

GENERAL

30

1

 I. FAILURE : RIGID PEDAL (ctd)

One of the rigid
brake pipes is it
smashed ?

 Dismount the brake caliper or

the brake cylinder?

 Replace the corresponding  rigid

pipe.

Are the brake

caliper’s pistons

or the cylinders

ones correctly

gliding ?

STOP

 Replace the defective parts

(with Genuine Spare Parts)

 Replace the brake pads, conse-

quently the brake shoes (see

bellow situations).

Are the brake pads,

consequently the shoes

gasket in good

condition?

     The brake linings are to be replaced when
they are: -greasy

-shiny
-not  in accordance with the

manufacturer’s prescriptions (genuine Spare
Parts have not been used).

Yes

Yes

No

No

No

DIAGNOSTIC

30 - 12

GENERAL

30

II.    FAILURE : LONG PEDAL

When braking, the brake pedal is slowly moving.

Perform a test with the stopped engine, after previously
performing five successive pushing on the brake pedal
(in order to vacuum the servobrake).

Locate and repair or replace the
item where a brake fluid leak is
established.

Yes

No

Is the brake fluid

level lower

compared to the

required one?

 Replace the brake  pump, because the pressure gas-
ket (sealing) between the primary circuit and the sec-
ondary circuit is defective.

STOP

DIAGNOSTIC

30 - 13