MORRIS MOTORS LTD.
SERVICE
INFORMATION
No. CO/2
MODELS:
MORRIS 11.9
H.P.
AND
14/
28
H.P.
INo.
OF
SHEETS
2 I
SHEET
No. 2
Date
of
issue:
July,
1928
Diagnosing Engine
Troubles-continued
(j)
Piston tightness.
(g)
Blow-back past piston
(a particular form
of
piston
knock).
(h)
Main bearing loose.
(i)
End
play on crankshaft.
(j)
End play on camshaft.
(k) Loose fan pulley, failing
to
pull up spacer on to timing
wheel.
(l) Ridges on cylinder walls
at the top and bottom
of
piston ring travel.
(m)
Tappet
loose in guide.
(n)
Valve squeak.
Causes a light clatter, resulting generally from bearing reaction consequent
upon the presence of new and tight pistons
or
over-tight gudgeon pin fits.
It
is
noticed at practically any speed, its intensity depending upon the degree
of
tightness.
In
the case
of
new engines so-called "
piston-slap"
is
nearly always due to
piston tightness, which will depart when the engine has become properly run in.
It
is
heard most distinctly when a new or refitted engine
is
pushed unduly.
The
withdrawal
of
existing pistons
is
a course .to be greatly deplored, since
it
will be
obvious from the above remarks that the trouble will only be aggravated.
These
symptoms are most pronounced on new cars, because the pistons have not been
afforded a proper opportunity of bedding down.
It
is
interesting to remark here
that some
of
the so-called "
dud
engines"
owe a great deal of their unfortunate
reputation to the fact that they have been tampered with in their early life, and before
a reasonable opportunity of settling down has been afforded.
It
is
a definite fact
that every Morris engine
is
carefully tested on the most up-to-date plant available,
and
then'
j,
no possible chance
of
an engine which
is
fundamentally faulty passing
through.
A sharp tap, either intermittent or constant at slow speeds,
but
continuous
under
load and particularly noticeable when picking up on top gear from a slow speed.
Can be cut
out
absolutely by shorting the sparking plug
of
the cylinder concerned,
thus relieving explosion pressure. Usually not heard over
30
m.p.h., and worst
when engine
is
cold.
This
noise
is
due, in ninety-nine cases
out
of a hundred, to
dry pistons.
The
truth of this statement can
be
proved by injecting oil into the
cylinder affected, when the tap will almost certainly vanish.
On
new cars the best course of action
is
to encourage continued running with
the sump well over-filled. Also upper cylinder lubrication
is
recommended by
the introduction
ofa
little engine oil in the petrol.
The
oil supply from the main
bearings, which lubricates the pistons, will increase
as
time goes on, and thus the
above expedients may eventually be dropped.
As
in the case of piston tightness,
we deplore the stripping of new engines for blow-back before at least
1500
miles
have been covered, and cases of this kind cannot in future be treated
under
the
guarantee.
This
ruling
is
made in the best interests of the future performance
of the car.
Heard mostly at fairly high speeds when pulling
hard-a
low knock. Can be
relieved by shorting the nearest sparking plug, and upon release
of
plug comes in
again with a thump. Bad main bearing knocks can be heard at slower speeds
under
load, and can also be felt on the steering column.
Main
bearing knocks can also
be heard when the engine
is
raced up with the car at rest.
The
noises described above must not be confused with the noise made by a loose
starter chain.
A slight rumbling, which can be heard mostly when the engine
is
idling, and which
can be steadied by slight pressure on the clutch pedal.
In
extreme cases pressure on
the clutch pedal accentuates the trouble and causes quite a heavy knock at crankshaft
speed-the
result of a crankshaft web fouling a bearing block. Liners for the
crankshaft front main bearing collars are available upon application to Service
(Parts) Department, or the
thrust
collars can
be
white-metalled.
A clatter, varying in intensity according
to
the amount
of
end play in existence.
Heard only when the engine
is
idling, and can be cut
out
by the pressure ofa hammer
shaft against the fan drive pulley. Take particular care when adjusting to allow
the .003" end float which
is
absolutely requisite.
Practically the same noise
as
in the case of camshaft end play,
but
somewhat
accentuated. Can be
cut
out
by hammer shaft pressure. Usually the looseness
can be felt by rocking the pulley circumferentially with the engine at rest.
The
symptoms are very like those shown under the heading
of"
Piston Slackness."
Usually, however, circumstances will suggest whether the clatter
is
the result of
piston slackness or ridges in the cylinders.
The
latter may be anticipated on a
fairly old car which has been refitted, although the ridges should have been relieved
considerably by scraping
or
lapping during the process of overhaul.
Sounds like a slack tappet, and can be located by pressing each tappet in turn,
with the engine running at a speed which causes sound to be most pronounced.
Naturally, all tappets should be checked for clearance before test takes place. May
be intermittent, due to the revolving action
of
the tappet.
Intermittent
chirp-may
become continuous if acute, at valve opening intervals.
Upper
cylinder lubrication and squirting the stem with oil
is
recommended in such
cases.
