MG MGB - Hydraulic pressure test

THE
OVERDRIVE
(TYPE
L.H.)
Fe
Section
Fc.2
FAULT
DIAGNOSIS
OVERDRIVE DOES
NOT ENGAGE
(1) Insufficient oil
in
gearbox
(2) Electrical
system
fault
..
(3)
Low
hydraulic
pressure:
(a) Pump
non-return
valve
not
seating
(b) Solenoid ball valve
not
seating
..
(c) Pump filter choked
..
(4)
Damaged
parts
within
unit
OVERDRIVE DOES NOT DISENGAGE
Top
up
to
correct
level.
Check and rectify fault; check
operation
of solenoid.
Remove
and check the valve;
clean
or
renew.
Remove and check the
valve;
clean
or renew.
Remove and clean
■lter.
Remove,
dismantle,
and
inspect unit.
NOTE.—
If
the overdrive does
not
disengage, do
not
reverse
the
car as
extensive
damage
may
result.
(5)
Electrical control
system
fault
(6)
.
Sticking clutch
(7)
Damaged
parts
within
unit
OVERDRIVE SLIPS WHEN
ENGAGED
(8) Insufficient
oil
in
gearbox
(9)
Low
hydraulic
pressure:
(a) Pump
non-return
valve
not
seating
(b)
Relief
valve
not
seating
(c)
Solenoid valve
not
seating
..
..
(d) Partially
blocked
pump or
relief
valve filter
..
(10)
Worn
or
glazed clutch lining
..
SLIP
IN REVERSE 0R
FREE WHEEL ON OVER-RUN
(l 1)
Worn
or
glazed clutch lining
.. ..
(12)
Broken circlip
on sun
wheel
Section Fc.3
HYDRAULIC
PRESSURE
TEST
)—|
Check
the
gearbox oil level,
and
top
up as necessary.
2.
Raise and
support
the
rear
of
the
car
so
that
the
rear
wheels
are
clear
of the
ground.
3.
Securely chock the front wheels.
Remove
the relief
valve plug and
its
sealing
washer.
Fit
adaptor
18G
251
E,
using
the relief
valve plug
sealing washer,
into
the relief
valve ori■ce.
6.
Connect
pressure gauge
18G
251.
Start
the
engine,
engage
top
gear
and select
overdrive.
8. Set
the speed
to
a
speedometer
reading of
30
mph.
(48 km.p.h.)
and
note
the
pressure
gauge
reading;
the
correct
reading
is
400
to
420
lb./sq.
in.
(28
to
29.5
kg./cm.2).
NOTE—No
pressure
reading will
be recorded with the
overdrive disengaged.
i
PM“
>‘
MGB.
Issue
1.
15676
Check and
rectify fault.
.
On
a new
unit
this
may
be due
to
insufficient
bedding-in
of
the clutch.
The clutch
can
usually be
freed
by
giving the
brake-ring, accessible from beneath the
car,
several sharp
blows with
3
hide mallet.
Remove, dismantle,
and
inspect unit.
Top
up
to
correct
level.
Remove
and check the
valve;
clean
or
renew.
Remove and check the
valve; clean
or renew.
Remove and check
the valve; clean
or
renew.
Remove and
clean
filters.
Remove, dismantle,
and replace
faulty
parts.
Remove, dismantle,
and replace
faulty
parts.
Remove, dismantle,
and replace
faulty
parts.
Fig. Fc.6
Pressure
gauge
18G
251
and adaptor 186 251
E connected
to
check the hydraulic
pressure
Fc.7