New-York tribune., 1917-05-06
What to Look For
List of Possible Reasons
Which Motorist Will Do
Well to Study
BY II. {. BR0kAW

totally different source. In fact. there
arc so many different kinds of knocks
that even an expert cannot tell always
just where it comes from without to-
tally disassembling the engine. Even
then it sometimes puzzles him lot by
its elusiveness.
Most engines have knock Of some
sort which annoys the driver, which
might vary from a barely perceptible
click TO a blow that may be heard by
persons standing on the sidewalk. A
great many of the knocks do not do
any harm. that is, they arc not caus-
ing any damage to the engine parts;
but there are some knocks which re-
quire immediate attention to prevent
the demolition of the engine or serious
" damaging it. Some of these are
loose connecting rod bearing; cylinder
loose on its base; lack of fabrication
and consequent overheating, and q
broken revolving or reciprocating mem
Der, which might tear things up If
allowed TO run. The spark advanced
TOO far puts an excessive strain on the
crank shaft and short circuit in the
ignition system does the same.
On the other hand, there is no I'M
mediate danger if there is piston
slap, though pretty noisy; nor is there
when the oil pump gives a thump or
loud click at the valve seating. But,
on general principles, when there is a
knock its cause should be ascertained
at once and expert advice obtained as
to whether it is dangerous. II so, 1t
must be fixed before running further.
If il is only minor knock the repair
can be left TO a more convenient time.
Sometimes the knocks arc hard to To-
cate. One of our cars needed a new
cam shaft gear to replace worn one
which produced a knock. It was put
on, but when the engine was started 1t
was found there was a worse knock
than before. 1t took long time to
find that it was the new gear. 1t fitted
very tight on the shaft and had to be
forced on. Without being noticeable,
the forcing had cracked the hub and
this cracked through the rim, so that
two of the teeth were out of true and
had spread enough to pound when that
portion of gear came into mesh.
Another knock difficult to locate is
caused by sticking exhaust valves. One
of the valve stems had. been oiled and
this had been allowed to burn to
nice. sticky paste. Now, when the
push rod opens the valve and starts
down the valve does not follow closely.
The spring brings it down, of course,
but more slowly than it should, be-
cause of the sticky stem, and wien
the stem and push rod meet there is a
thump.
1t is ordinarily said that lean MKT
ure or an oyeradvanced spark will
cause knocking As matter of fact,
they do not do anything of the kind;
but it is true that these things bring
to our notice other faults. such as worn
piston or cylinder wall and consequent
side slap, or they magnify some other
worn part so that it becomes audible.
As a matter of fact, it is possible to
try to reverse the engine and not
have a particle of knock. And it is
possible TO have so lean a mixture it
knock; but if there is something else
wrong it will bring that out.
Some of the causes Of knocking have
been collated and are given for the
instruction Of the novice.
Mechanical Looseness, Due to Improper
Adjustment or Wear
Loose connecting rod bearing, crank
pin end.
Crank pin bearing out of round.
Main bearings of crank shaft loose.
Bearings too tight
Wrist pin loose in piston.
Wrist pin loose In upper end of con-
Meeting rod
Wrist pin not in line with crank
shaft. causing side slap.
Piston ring loose in slot or broken.
Cam follower guide worn.
Cam loose on shaft.
Cam shaft bearing worn.
Worn cam (flat spot.
Fly wheel loose on crank shaft (old
models with keyed-on wheel.
Fly wheel out of balance.
Timing gears loose on shaft.
Worn or broken timing gear teeth.
Cylinder loose at its base.
Engine loose from frame.
Piston too small for cylinder, caus-
ing side slap.
Poor push rod adjustment-ga too
great.
Exhaust or inlet valve sticking in
guide.
Spark plug touching valve.
Magnetic coupling loose.
Fan belt coupling striking a pulley
Fan blades striking something.
Worn cylinder, causing side slap.
Bent crank shaft.
Faulty Ignition
Spark advanced too far
Spark too late, causing overheating.
Chart circuife ia iOpitfop svctop1
causing irregular spark.
Spark plug points constructed wrong,
causing them to overhead.
Spark plug in poor position.
Wrong timing of ignition system; too
early. too late. or wrong order.
Dirty distributor, misdirecting the
current.
Faulty Carburetion
Pre-ignition, due to excessive carbon
deposits.
Rich mixture. causing overhesting.
Lean mixture, in conjunction with
worn parts.
Faulty Lubrication
Lack Of oil.
Lubricants of poor quality.
Excess of oil, causing carbon de-
posit.
Oyerheating Of Engine
Fan not working
Pump parts not revolving.
Radiator clogged.
Pipe lines clogged.
Rubber hose defective inside. block
! ng flow Of water.
Ignition timed too late.
Faulty Compression
Engine designed with too high com
preston, causing pre-ignition.
There are, of course, many other
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