Gus Wilson put down his paper and
glanced out of the living room window just as his next door neighbors, the
Benton's returned from their weekly travels with Sunday afternoon traffic.
"Dan seems to be taking it slower than
usual," thought Gus as the car passed at a snail's pace and came to a stop
Benton's house "The missus must be back
seat driving. Fifteen miles an hour isn't that lad's speed."
When his wife, four children and pet dog
were safely inside the house, Dan Benson climbed the steps to Gus's porch
and held a finger impatiently and insistently on the doorbell button.
"Sorry to bother you, Gus, especially on
your day off," Benson apologized when Gus opened the door, "but something's
wrong with that car of mine and I'm scared to drive it as far as my garage.
On the way home, it acted like
the engine was falling apart. All of a
sudden the steering wheel began to wobble and the further I drove the worse
it got. Every time I'd start up in traffic, the whole car would shake and
the motor sounded like the "anvil chorus'."
"So that's why you drove by as though you
were going to a funeral," Gus chuckled as he took down his hat and coat.
When they reached Benson's car, Gus slid
into the driver's seat and motioned to Dan to sit beside him. "Let's take a
ride around the block," he suggested as he pressed the starter.
"Doesn't sound so bad when it's idling,"
muttered Gus as he leaned forward to get his ear nearer the motor. "It
seems to run fine at high speed too."
Gus shifted into low gear and cautiously
released the clutch pedal. The whole car began to vibrate as the motor
groaned and the car jerked unsteadily ahead. Gus again tilted his head and
"I don't think it's your motor," he
bellowed over the clatter. "It must be your clutch or drive shaft. Let's
go down to the garage so I can run it up on the greasing rack and give it
the once over from underneath. Joe Clark, my partner, is down there trying
to catch up on the unpaid bills. He'll be glad to see us."
Wasting little time, Gus soon had the car
raised on the rack and was busily rolling up the sleeves of his Sunday
"Holy smokes, " he grunted as he glanced
up at the underside of the car. "You've sure been riding with Lady Luck and
didn't know it."
Joe Clark and Benson looked in the
direction he indicated. "The front end of your driveshaft's just about ready
to come loose. That connection between the transmission and the front
universal should have six bolts holding it together. Four have dropped out
and the two that are left are on the same side of the flanges and about
ready to drop out too. If that drive shaft had dropped when you were going
fast, the front end would have dug into the road sure as shooting and lifted
the rear of your car into a front somersault." "But, Gus, "Benson asked
bluntly when the gray-haired mechanic had replaced the missing belts, "what
made all the noise? I could have sworn it was in the motor."
"Being loose, the connection buckled
every time you gave it the gas. You see," Gus explained, using his hands to
demonstrate, "the universal was connected to the transmission shaft only at
one point where the loose bolts were. Naturally there was a lot of play and
every time your motor putted, the two connecting flanges twisted and hit
against the two loose bolts. Being connected off center, the shaft vibrated
and the whole car rattled as though falling apart."
"It certainly sounded as if a main
bearing was falling to pieces," Benson insisted. "That's the trouble with
most car owners," Gus said jokingly as he wiped his large, greasy hands on a
convenient piece of waste. "Every time you hear a rattle or a noise you
think it's the bearings. Nine times out of ten, it isn't."
"Motor knocks generally occur in cycles.
The majority of knocks people hear are nothing but valve noises. You've got
a valve tap in that motor of yours, but I wouldn't advise tightening the
tappets, because tight tappets wear faster. "Most times, a motor knock comes
from nothing more than carbon, advanced spark or a poorly adjusted
carburetor. It's best to look for the common troubles before you blame the
bearings or pistons. I've had people come in here with great tales about
bearing knocks and lots of those have turned out to be motors caused by
loose motor fittings or bolts."
"But how can you tell one knock from the
other?" asked Benson, intent on learning all he could. "The best way is
to take the car out on the road and drive it along about fifteen miles and
hour; ordinary motor noises don't speak up so loudly at that speed. I
generally include a few hills in the ride too.
"If I hear a light knock that gets louder
when the car climbs, loose piston rings, or a loose piston. If the knock
has a muffled sound I mark it up against a worn connecting rod. A pounding
engine sometimes means a worn crank-shaft bearing. In your case, is meant
that something was loose inside the motor."
"But that's all guesswork," Benson
objected, "Isn't there some way you can tell for sure just what the trouble
"An auto mechanic," smiled Gus, "is
like a detective. He doesn't make any accusations until he's pretty
sure. A little brain work in the beginning will save a lot of
expensive ton of work later on. You've got to go about things
systematically and find the trouble by eliminating one possibility after the other.
"After a good mechanic gets
some hunch by using his ears, he can generally run down the actual trouble
by making common sense tests. For instance," Gus led the way to a car parked
by the repair bench at the back of the garage, "I took this car out for a
test run yesterday and from the noise it made I decided a connecting rod was
loose. "Now I'm going to test the bearings by running the motor at idling
speed and short-circuiting the spark plugs one at a time."
He picked up a rubber-handled screwdriver
and shorted the cylinders in turn.
"Nothing's happened so far," he said,
placing the shock of the tool on the third plug, "but listen to this
When the engine was running with all
cylinders, a definite metallic knock could be heard, but when Gus cut out
one cylinder by shorting the spark plug, the noise got fainter and changed
to a double knock instead of a single rap.
"That's the cylinder," announced Gus.
"Now I won't have to bother about the rest. You can always locate bearing
or piston trouble by cutting out the explosion on the cylinders one at a
time. A difference is the sound of the knock will generally tell you that
the short-circuited cylinder is the one causing the trouble. Of course, two
or more cylinders may be at fault, but you can generally sort them out by
repeating the test several times."
"What do mechanics mean when they speak
of 'piston slap'?" Benson asked when Gus had closed the hood on the car.
"That's a knock caused by a worn piston hitting against the side of the
cylinder at the beginning of each power strike," Gus explained. "You can
generally spot the right cylinder by short-circuiting. If the knock stops
when a particular cylinder is cut out, that cylinder contains the worn
piston. "Piston slap is a funny thing, though. A cold motor will often
have a piston slap that'll disappear when the motor heats up and the parts
expand. If it's a real case of piston slap, all you can do is pull down the
motor and fit oversize pistons and see that the connecting rods are properly
When Benson had dropped Gus off in front
of his house, the old mechanic looked over his shoulder and smiled. "I
wouldn't worry too much about all the squeaks and rattles you hear when
you're driving a car," he said. "A motor's bound to make some noise when it
gets old. But it's only the queer thumps and knocks that mean real