Brake fluid
78491R
GENERAL
Brake unions and pipes
30
The connection of the pipes between the master
cylinder, calipers, compensator and the hydraulic
assembly is made using threaded unions with a
METRIC THREAD.
Consequently, only parts specified in the Parts
Catalogue for this vehicle should be used.
Identification of parts
- SHAPE of the ends of PIPES in steel or copper
(A),
- SHAPE of the THREADED LOCATIONS on
components (B),
- pipe UNIONS coloured GREEN or BLACK:
HEXAGONAL OUTSIDE 11 mm or 12 mm (C).
BRAKE FLUID RENEWAL FREQUENCY
Braking technology, in particular for disc brakes (hollow pistons which transmit little heat, low volume of
fluid in the cylinder, sliding calipers avoiding the need for a fluid reservoir in the least cooled area of the
wheel), has allowed us to avoid the risk of vapour lock as far as possible, even if the brakes are used
intensively (in mountainous areas).
Modern brake fluids still degrade slightly during the first few months of use due to a small uptake of
humidity and replacement of the fluid is therefore recommended (refer to vehicle’s Warranty and Servicing
Handbook).
Topping up the level:
Wear of the brake pads and shoes will cause a gradual drop in the fluid level in the reservoir. This drop should
not be compensated for since the level will rise again when the pads are changed. The level should not
however be allowed to fall below the minimum mark.
Approved brake fluids:
Mixing two incompatible brake fluids in the circuit will cause a risk of major leaks, mainly due to
deterioration of the cups. To avoid such risks, it is important to use only those brake fluids which have been
tested and approved by our Technical Department and which conform to standard SAE J 1703 dot 4.
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ELECTRONICALLY CONTROLLED HYDRAULIC SYSTEMS
BOSCH ABS
38
HYDRAULIC BRAKING TEST
This section describes the test to be carried out using the XR25, to check the mounting of the ABS system in
the vehicle and, in particular, the hydraulic circuit.
NOTE: for this test, two persons are required and the vehicle must be on a two post lift, if possible.
Principle of the test
Put the vehicle on the lift with the wheel to be tested raised. One of the operators must be in the passenger
compartment in the driver’s position with the XR25. Switch the ignition on, vehicle in neutral, in fault finding
mode and press the brake pedal. The second operator must apply a torque to the wheel to try and rotate it.
The operator generates an appropriate command on the XR25 which carries out the following cycle ten
times: alternate decrease then increase in pressure at the wheel to be checked. These actions in the ABS will
be noted at the wheel as ten alternate locking and releasing operations. The jerky movement of the wheel,
noted qualitatively by the operator, signify that the hydraulic circuit for this wheel is correctly connected.
The programme for the XR25 for this sequence is as follows:
- Cycle on the wheel to be tested:
- a drop in pressure for 200 ms where the pump starts at the same time,
- an increase in pressure for 300 ms where the pump starts at the same time (ten cycles are carried out
for the wheel in question).
- The pressure increases to master cylinder pressure for all four wheels.
- The hydraulic pump motor stops.
- The operator releases the brake pedal.
The hydraulic test for the wheel in question is complete - begin the test for the three other wheels.
BLEEDING PROCEDURE
NOTE :
the hydraulic assembly is pre-filled.
This bleeding procedure must be used when one of the following components has been removed:
- the hydraulic assembly,
- the master cylinder,
- the pipework (between the hydraulic assembly and the master cylinder).
1)Bleed the braking system conventionally using the pedal.
NOTE : if, after a road test with ABS regulation, the pedal travel is not correct, bleed the hydraulic assembly.
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