For the tenth time, John Knowles glanced
apprehensively at his oil gauge and nervously tapped its glass cover to
reassure himself that the needle hadn't stuck.
Then, to make doubly sure, he threw out the clutch and took his foot
off the accelerator so that the motor slowed to idling speed.
The oil-gauge needle immediately dropped to a few pounds instead of
its normal position near the thirty-pound mark.
When he speeded up the motor and let in the clutch again, the needle
swung up to its former position.
"That settles the oil-pressure question,
all right," he muttered to himself.
"So whatever that confounded squealing is, it certainly isn't coming
from a dry bearing in the motor.
With all that oil pressure, I don't see how any bearing could run
dry."
The noise continued, however, and was
very pronounced when he had to go slowly in traffic.
"I just hope I can get to Gus's place
before there's any damage done," Knowles grunted, as he rounded a curve and
the sign of the Model Garage came into sight.
Gus Wilson, mechanic and half owner of
the establishment, slid open the door at the sound of Knowles's horn.
"Where'd you get the canary?" he asked
with a grin, when he heard the chirping squeal that was coming from under
the hood of the car.
"Is it something serious?" Knowles asked
nervously, after he had stopped in the shop.
"Serious!" Gus grunted, walking over to
the car and lifting the hood.
"There's no noise a car can
develop that sounds worse and means less than that commutator squeal.
That's what you've got.
Ordinarily, the brushes of the generator slide on the surface of the
commutator without making any noise.
But once in a while, when conditions happen to be just right for it,
the commutator takes on a glaze that causes the brushes to vibrate like
violin strings when you scrape a bow over them.
"If you just forget about it," Gus
continued as he lifted the hood and applied a screw driver to the dust band
over the commutator, "the chances are about a thousand to one that the noise
will go away in a day or two, and you may never hear it again as long as you
own the car. Or it may come back
from time to time. If you want
to get rid of the squealing, all you have to do is to clean the commutator
like this."
He took a small flat-ended stick, pulled
a piece of stout cloth over the end of it, and pressed it against the
spinning commutator. The noise
stopped at once.
"Always use a piece of wood, never the
end of a screw driver," Gus cautioned, "and a stout piece of cloth that
won't tear into shreds and get caught under the brushes.
If it still squeals a bit after a cleaning like this, put just the
tiniest trace of petroleum jelly on the cloth and try it again.
That'll cure the most stubborn case of commutator squeal you'll ever
run across."
"That's a relief, Gus," said Knowles.
"Put it on my bill."
"That'll be a big item," Gus laughed.
"Killing one canary - ten cents.'
Forget it!"
"All right, then, fill up the gas tank
and check the oil," Knowles smiled.
"I suppose you think I'm an awful
nuisance, Gus," he went on, after he had backed the car out to the pump,
"but I can't help worrying when I hear any funny noise."
"It's a lot easier on your pocketbook to
be that way," Gus grunted, as he unhooked the gas hose and started the pump
motor, "Gus grunted, as he unhooked the gas hose and started the pump motor,
"than it is to be one of those birds who never suspect there's anything
wrong 'til the wheel drops off or the motor quits cold.
"The big think," he continued, "is to get
to know which noises mean things that don't amount to much - like that
commutator squeal, for instance - and the noises that spell trouble coming.
Take brakes that howl just as you come to a stop.
There's a noise that doesn't necessarily mean that the brakes are
going had. Sometimes after a
couple of thousand miles, the brakes on a new car will develop a squeal that
will last for a few days and then go away for good.
Or they may only how! In very dry weather, or when you get them
soaking wet. The important thing
is whether the noise keeps up, or whether it comes only once in a while and
then disappears. The same thing
applies to chattering brakes, because a chatter and a howl are a about the
same thing. Both are vibrations
caused by some particular condition of the brake lining and the brake drum -
usually a glazed surface on the brake lining.
A long run down a mountain with the brakes partly on may put a
temporary glaze on the surface, but it will disappear after a few quick
stops. Of course, if the car has
seen many thousands of miles of hard service, and the brakes suddenly begin
to chatter or squeal continually, they ought to be checked right away."
"Are there many other noises I'm likely to hear that don't mean
real trouble?"
"Sure plenty of 'em," Gus replied, as he
put the end of the hose back on its hook.
"Sometimes, on a cold morning, while you're letting the motor warm up
a bit, you may hear a sputtering, gurgling noise from under the car.
Don't let it worry you.
It'll be water, condensed from the exhaust fumes in the muffler, being
forced out the vent hole.
If you se a small puddle of water on the floor after you drive the car out,
that's probably where it came from.
Then, if you hear a 'slap, slap, slap,' noise when you drive onto a
smooth concrete road from a dirt road or from your own bluestone-covered
driveway, it probably isn't a piece of the tire tread coming loose, but a
small stone wedged into the tread.
If the noise doesn't stop within a quarter mile or so, it isn't a bad
idea to get out and investigate.
There's always a chance that it's a nail or a piece of scrap metal.
"There's another noise that sounds like
trouble but doesn't mean much," Gus continued as he directed a golden stream
of oil into the filler hole.
"That, is a sort of a ticking rattle that comes from one of the
wheels just as the car stops.
It's a lot like the sound we used to get from a loose demountable rim in the
days when cars had such things.
But, while a loose rim in the old days might mean a tire coming off on the
road, the noise you hear nowadays means only that the large snap-on cap over
the hub of the wheel is a bit loose.
If it fell off, you'd have to buy another one, but the operation of
the car wouldn't be affected."
"How about some of the noises that are real danger signals?"
Knowles asked, while the mechanic was
rechecking the oil level.
"There's one that a lot of people don't
listen for," Gus replied, "and that is the rather sharp click accompanied by
a slight jar, that comes when you have backed and you let in the clutch to
go forward again. If you hear
that sort of a noise, you'd better check up on the tightness of the back
wheels on the hubs. If a wheel is
loose and is sawing back and forth against the key, the key may be sheared
off and the wheel will be free n the shaft - which means a tow-in job.
Or else the end of the shaft may snap off, and then you will be in
trouble."
"Sometimes I hear a slight click if I don't have the motor going
at the right speed when I let in the clutch after shifting gears," Knowles
remarked. "Is that the
same thing?"
"The click you hear then is mostly the
taking up of the play - or, in other words, the backlash in the whole drive
from motor to rear wheels," Gus explained.
"You can get that sound in most cars, no matter how tightly the
wheels fit."
"How about motor noises? Is it easy to
learn to tell which noises mean that real trouble is coming?"
"How are you going to do that," Gus
countered, "when most of the things that mean trouble coming to the motor
don't give any warning noises?
The noise comes after the damage is done.
Take the oil supply, for example.
If it fails and you don't happen to notice the lack of pressure on
the gauge, or the increase in motor heat on the dash thermometer, then the
first thing you know about it is when a heck of a lot of clattering and
clanking tells you that a hearing is shot, or when the motor stops because
the pistons stick. Al that your
ears can do is to tell you when something has gone wrong - not when it is
about to go wrong."
"Now I think of it, I can see that it
would have to be that way," Knowles admitted, "because the engine parts move
at such high sped and fit so closely.
As long as they fit, they can't make any funny noises - and when
anything happens to make 'em loose, the damage is already done.
Are there any other important things to listen for, outside of the
motor?"
"Well," said Gus, wiping his hands on a
wad of waste, "if you hear a grating and grinding noise from a front wheel
and you feel a slight drag on the steering wheel on that side, slow down at
once and head for a repair station, because you've probably broken a
front-wheel bearing."
Knowles climbed into his car and started
the engine.
"Thanks a lot, Gus," he said.
"I suppose this listening for noises is a necessary evil of motoring,
eh?"
"It isn't for one of my customers,
anyhow," grunted Gus.
"How's that?" Knowles asked.
"Is he one of those 'I should worry' drivers?"
"He's just as fussy as you are - but he's
stone deaf!"
END
