What Car Noises, Smells & Drips Mean

What Your Car Is Trying to Tell You



Eric Peters


Cars often give their owners plenty of warning -- in the form of new
noises, odors and other signs -- before a mechanical failure occurs.
Here are some danger signs and what they may mean...

Noises

Metallic tapping/clicking from the engine. If you hear a new sound
such as this, it probably means you're low on engine oil -- a
condition that could burn out the engine. Check your oil, and fill it
up if necessary. If the metallic tapping/clicking persists, you might
have a failing oil pump or a problem related to the valve train, such
as a collapsed hydraulic lifter. (Lifters actuate the valves, which
let fuel into and exhaust out of your engine.) Take your car to a shop
as soon as possible to avoid potentially serious damage. Comfort: If
the sound has been there a long time, it just might be an indication
of a heavily worn, high-mileage engine.

Under hood screeches. If you hear screeching when accelerating or
turning the steering wheel, you might have a loose or worn-out drive
belt... low power-steering fluid... or a failing water pump, a device
that circulates coolant through the engine to keep it from
overheating. Major damage can occur quickly from overheating, so stop
driving the car if a problem of this sort crops up.

If you are a bit handy, you can top off your power-steering fluid by
following the instructions in your owner's manual. Otherwise, take the
car to a repair shop.

If the power-steering fluid is too low, the power-steering system will
eventually fail, the car will be much more difficult to steer and you
might not be able to maintain safe control.

Drive belt and water pump problems need a mechanic's attention. Don't
wait long. If the water pump fails (or the "serpentine" belt that
drives it and other accessories fails), the engine will quickly
overheat -- and you will lose the use of all power-assisted devices,
so pull over as fast as you safely can.

Clunking or "ka-thumping." If, when you put your car into drive (or
put a manual transmission car into a gear), you hear a fairly loud
clunking or ka-thumping sound, you may have a worn-out universal joint
-- the flexible joint that connects the transmission to the driveshaft
and the driveshaft to the axle. This is not necessarily an emergency,
but if you let it go on too long, the joint could fail. Then your
driveshaft could come loose, possibly striking the ground and even
pole-vaulting the vehicle into the air.

Knocking. Many late-model cars with modern engines keep running
smoothly regardless of whether you put in regular (low-octane) or
premium (high-octane) fuel, so you won't hear the knocking or pinging
that is a classic sign of too-low-octane fuel. (You will, however,
suffer decreased fuel economy and less horsepower if you use the wrong
gasoline.)

With cars built before electronic controls became commonplace in the
late 1980s, gas with an octane rating below the recommended minimum
may cause premature combustion, and you'll hear the knocking or
pinging. That is a sign of great stress on internal engine components.
In these cars, extended use of low-octane gas can cause severe engine
damage.

Another kind of knocking: If you ever hear very loud knocking coming
from the engine compartment -- so loud that it's impossible to drown
it out with, say, the radio -- it could signal a major problem, such
as a "spun" (loose) crankshaft bearing or connecting rod failure,
either of which can cause major -- perhaps irreparable -- damage. A
sudden loss of oil pressure (caused by, say, the oil drain plug
falling out) could also cause a racket.

When your car makes any very loud noise, immediately pull over and
turn off the engine -- that may limit the damage. Then arrange for a
tow.

Under car sputtering. This usually means a leaky exhaust system.
Typically, the sound gets more obnoxious the harder you push on the
gas pedal -- and in particular, when you suddenly lift off the gas.
Get this checked out quickly because a leaking exhaust system can
allow dangerous fumes into the car's interior.

Whining or screeching that's not from the engine. This could indicate
a problem with the automatic transmission's internal pump, which
circulates hydraulic fluid that lubricates and powers the
transmission. The noise might be accompanied by late or erratic
shifting from gear to gear or "slipping" (you press on the gas and the
engine revs, but the car doesn't move forward right away).

On manual-transmission cars, a worn or out-of-adjustment clutch may
"chatter," sending vibrations through the clutch pedal. When it is
very worn, it will cause the same kind of gear slippage that you might
experience with a worn automatic.

Smells

Oily-sweet. This is the smell of engine coolant -- and if you smell it
inside your car, you could have the beginnings of a real mess. It
could be a leaking heater core -- a small, radiator-like part buried
deep inside your car, often in between the engine and the passenger
compartment. When it fails, it can allow hot, smelly (and oily) engine
coolant to seep into the car's interior and soak the carpet. Another
clue: An oily/foggy film on the inside surface of the windshield and
the front passenger window, near those windows' defroster ducts. In a
pinch, a mechanic might be able to stop the leak by redirecting
coolant away from your heater core -- leaving you without a working
heater. Ultimately, your heater core will have to be replaced.

Rotten eggs. An occasional rotten egg smell may not be a problem.
However, if this smell persists, it typically is a sign of an
emissions-control problem, usually having to do with the car's
catalytic converter. As this is expensive, you want to have the source
of the trouble located and dealt with as soon as possible, before you
face a bill for a ruined converter.

Drips

Fluid slowly leaking from your car -- other than water that has
condensed when you run your air conditioner -- is often a sign of a
serious issue. See a mechanic right away.

Reddish brown drip. You may have a leaking transmission -- maybe just
the pan gasket (from overtightening) or maybe because of something
more serious, such as a leaking front seal.

Green or orange-red drip. This suggests cooling system trouble --
generally a leaking radiator or hose.

Molasses-to-blackish-colored, thick drip. This is probably engine oil.
If your car is more than two or three years old and/or has more than
20,000 miles or so on it, and you're seeing just a few drops per day,
it's probably nothing to worry about. All engines eventually drip a
little oil. But when you see more than that -- especially anything
that could be described as a "puddle" -- it could be a sign of a
serious problem. Also, if your car does drip oil, be sure to check the
oil level frequently and top it off when necessary. And when you
drive, keep a close eye on your oil-pressure gauge (or dashboard oil
warning light). If the pressure drops unusually low or the light comes
on, turn off the car immediately (in a safe spot), and check and add
oil. Never run an engine with low oil pressure or an oil warning light
on -- unless you don't mind paying for a new engine.


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Bottom Line/Personal interviewed Eric Peters, an automotive columnist
based in Washington, DC, and author of Automotive Atrocities! The Cars
We Love to Hate (MBI). Readers may contact him at Peters at
BottomLinePersonal.com.