Sunbeam ALPINE I SERIES: APLINE II SERIES, Workshop Manual, Page: 295 / 413

Page 36
TESTING EQUIPMENT
To make comprehensive tests, of the vacuum servo
unit, requires complex and expensive equipment
and this kind of testing is outside the capacity of
many Service Workshops.
A number of simple tests can be made when the
servo unit is installed which gives some useful
information and these tests are described here­
after. The only piece of equipment required is a
i
w
x 24 U.N.F. pipe union to fit into the hydraulic
Inlet port.
The use of these tests will assist in diagnoses and
will provide assurance after servicing, but the tests
are not exhaustive and so cannot equal the stan­
dard of the testing which is done In the factory
by the specially designed equipment. If a vacuum
servo unit gives cause for doubt It Is always best
to replace it with a factory tested unit when ever
possible.
IT IS ASSUMED THAT ANY FAULTS CON­
NECTED WITH THE BRAKE SYSTEM, SUCH
AS FLUID CONTAMINATION, LACK OF AD­
JUSTMENT, AIR IN THE HYDRAULIC SYSTEM,
FLUID LEAKS, ETC., HAVE BEEN RECOGNISED
AND ELIMINATED.
Test I
I. Fit the servo unit to the mounting bracket
and before connecting, the air or fluid pipes
fit a bleed screw to the fluid outlet port and
the special adaptor to the fluid inlet port.
2. Connect the vacuum pipe from the engine
Inlet manifold to the adaptor and remove
the air filter element.
· 3. Start the engine and while "ticking over"
place the fingers over the air Inlet port of
the air filter and the vacuum port to deter­
mine if there is any suction at either orifice
4. If suction can be detected, it Indicates that
the bores are scored or the components
Incorrectly assembled
5. Remove the adaptor.
Test 2
WSM.124
Section K (Brakes)
I. Connect the vacuum pipe from the inlet
manifold to the vacuum port.
2. Connect the fluid inlet and outlet pipes to
their respective ports and bleed the hydraulic
system of alr.
3. Start and run the engine. While the brake
Is being applied, It should be possible to hear
the hiss of the air Inlet and with the hand on
the vacuum cylinder feel the movement of
the piston Inside the vacuum cylinder.
Test 3
I. Start and run the engine for half a minute
then switch off and leave for two minutes.
2. Apply the brake and the servo unit should
operate and the operation should be detected
as described in Test 2.
Test 4
Start and run the engine, apply the brake hard
and hold it on for fifteen to twenty seconds.
There should be no perceptible creep in the
brake pedal.
If there is any creep, it indicates leaks or scored
bores in the components.
Test 5
I. Jack up the front roadwheels.
2. Start and run the engine.
3. Apply the brake and release.
4. The front roadwheels should be free to
move half a second after the release of the
pedal.
Tests 2 to 5 can be used to test a suspect Vacuum
Servo Unit before it Is removed from the car.
IF THE RESULT IS UNSATISFACTORY ON:­
Test 2. It means the servo unit Is not working at
all, which could be caused by a lack of
vacuum, possibly a faulty non-return valve,
or a fault within the servo unit.