ENGINE
(iv) Incorrect valve timing.
(v) Poor quality fuel.
(vi)
Mixture is too weak or excessively
rich.
(vii) Pre-ignition due to various causes.
(viii)
Air
leak into induction system
giving rise to a weak mixture.
(ix) Valves, particularly inlet, not
seating correctly.
(X) Defective cylinder head gasket.
Excessive
Oil
Consumption
Excessive oil consumption is usually
associated with a very worn engine, but
can
arise as a result of external leakages
and due to other factors with com-
paratively new engines.
If excessive oil consumption is estab-
lished, before commencing to dis-
mantle the engine a check for external
leakage should be carried out.
When an engine is burning oil it will be
indicated by the emission of bluish
grey smoke from the exhaust when the
engine is
"
raced up
"
after a period of
idling.
A
check for external leakage
can
be
conveniently carried out by spreading
paper on the ground under the forward
part of the car, and running the engine
at a moderate speed for a few minutes.
In this way it is possible to locate the
position of leaks which, without the en-
gine running, would not be evident.
External leaks are caused by one or
more of the following
:-
(i) Cracked sump or poor sump
packing.
(ii)
Flange faces of sump not true.
(iii) Drain plug loose or defective
packing washer.
(iv) Defective filter packing, poor joint
faces or loose attachment bolts.
(v) Oil pressure pipe line leaking.
(vi) Defective petrol pump packing,
pr joint faces or attachment
nuts loosened.
(vii)
Defective rocker cover packing,
poor joint faces or attachment
nuts loosened.
(viii) Defective front engine plate pack-
ing or poor joint faces.
(ix) Timing cover oil seal defective.
(X)
Timing cover cracked, defective
packing or loose mounting bolts.
(xi) Leakage round camshaft welch
plug.
(xii)
Unsuitable grade of oil or ex-
cessively diluted, arduous driving
conditions, excessively high pres-
sure or crankcase temperatures.
(xiii)
Excessive clearance between
piston and sleeve or incorrect
replacements, damaged
r+gs,
rings stuck in grooves,
insufficient
piston ring end gap, piston rings
exercising insufficient radial
pressure.
(xiv) Excessive diameter and axial
clearance
.
due to wear associated
with the possibility of oval and
worn crankpins.
(xv)
Excessive diameter clearance
in
main bearings and/or worn jour-
nals. (See page
l
for dimensions
and clearances.)
(j)
Low
Oil
Pressure
The correct oil pressure is
40-40
lbs.
per sq. in. for top gear for road speeds
between
30
-
40
m.p.h.
(48
-
64
km.p.h.). With complaints of low oil
pressure the following possible causes
should be investigated
:-
(i) Insufficient oil in sump.
(ii) Unsuitable grade of oil or a very
badly diluted supply.
(iii)
Suction oil filter restricted by dirt
in sump.
(iv) Oil pump loose on mountings.
(v) Very badly worn or damaged oil
pump.
(See
"
Oil Pump
"
on
page 13.1
To Next Page
Loading...
