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Love That Old Car Smell!

Follow your nose to diagnose car trouble

Everyone loves “that new-car smell.” But recognizing “those old-car smells” will save you money, prevent you from getting stranded (which inevitably happens when it’s raining, you’re late for something important, you’re not in the best part of town, and your cell battery is dead), and may help you avoid an accident. Unfortunately, many people treat old car smells the same way they deal with other unpleasant odors—either they ignore them or make comical attempts to cover them up. With old car smells, this will only make things more expensive, perhaps even tragic.

Even if you aren’t a do-it-yourselfer, knowing these “old car smells” will allow you to aim your mechanic in the right direction. (If our descriptions of old car smells confuse you, pull the appropriate dipstick or open the reservoir in question and give a sniff.)

Just A Spark

Gasoline is the worst possible old car smell. A tiny spark can turn an annoying odor into a raging inferno. While attempting to be a Good Samaritan, I once used up a 10-pound extinguisher on a fellow motorists’ small underhood fire: The fire returned instantly and I stood by helplessly while the poor guy’s car was incinerated. A car burns hot and fast. And the stink stays in your nostrils for days. Now imagine parking a car with a gas leak in a garage that contains a water heater, clothes dryer or furnace, all of which have constantly burning pilot lights.

Gas odor can come from something as simple as overfilling the fuel tank—adding gas after the pump’s automatic feature clicks off—or a faulty gas cap. Problems with the fuel vapor canister—perhaps it was cracked in an accident or its hose is plugged—is another source of gas fumes. Much more serious is a cracked fuel line, a leaking connection along that line, or a problem with the fuel injection system. Trace the system with your nose: The source will be obvious. If you find leaking or puddling gasoline, have the car towed to the dealer or mechanic. Or get a 20-pound fire extinguisher for the trip. Two would be better.

Sweet But Deadly

An approaching cooling system failure is the best thing indicated by the sticky-sweet smell of anti-freeze. That sweetness can also signal a tragedy in the making. The puddle of sweet-smelling, greenish fluid under your car is an attractive but deadly poison to dogs, cats and children. Do-it-yourselfers: Keep pets and children away when changing anti-freeze. Place the used fluid in a sealed container and take it to a recycling center or an auto parts store that accepts used antifreeze.

Some under-car puddles are benign: These include water condensing off the air condition system or rain (or windshield wiper fluid) dripping through drain holes in cowl. Rub a bit between your fingers and give it a sniff. If it’s oily or smelly, you’ve got a problem. If you’re still unsure, park over a clean piece of cardboard and take the tainted area to your auto parts store or mechanic for analysis.

The sweet smell of a coolant leak can come from a failing water pump or cracked radiator hoses. These hoses include those that carry hot coolant to the heater core mounted in the passenger compartment. If you smell antifreeze inside the car but not on the outside, either the hose to the heater core or the heater core itself is leaking.

Rotten Eggs

If a fog of rotten egg smell seems to follow your car around, it’s likely there’s a problem with your catalytic converter. The cat could be old, failing and clogged, or overworked by an improperly functioning engine management system.

A Preview of Eternal Damnation

The fiery sulfur springs in hell can’t smell much worse than overheated gear oil. While changing a transmission the night before a race (more like early morning before a race) I got used gear oil in my hair: I had to get it shaved off so I could sleep with myself. This thick gear oil is used in differentials of rear-drive cars, manual transmissions, and transfer cases of four-wheel-drives. It smells terrible even when new. Gear oil smells most often come from a leaking seal. Or the last person to change the gear oil cross-threaded the drain plug, over-tightened the plug or failed to install a new gasket under the plug.

Bad Medicine

If you get a whiff of something that smells like the worst oily, slightly sweet (but not in a good way), alcohol-based medicine you had to take as a kid, it’s brake fluid. This slippery hydraulic fluid is used not only in the braking system but also to operate the clutch in a manual transmission car. When new, it looks like apple juice, but old brake fluid can be near cola-colored.

Hunka Burnin’ Oil

Engine oil smells show up several ways. Oil can drip onto something hot, in which case the oily odor is mixed with a smoky aroma. (While oil dropping onto the exhaust manifold or catalytic converter won’t immediately burst into flame, just give it enough time and temperature.) Clean engine oil leaking from, say, an over- or under-tightened oil filter, has a lightly sweet smell. Older oil will have a harsher smell.

Light But With An Oily Bouquet

Automatic transmission fluid is much easier recognized by its thin viscosity and red color than by its smell. Clean ATF has little odor, much like a light lubricating or cooking oil. ATF in need of a change will smell a lot like engine oil in need of a change. A transmission with a serious problem begins to smell like gear oil. Power steering fluid, when new, smells similar to ATF but with a more oily aroma: kind of like a penetrating oil.

Burning Rubber

The acrid odor of burning rubber often comes from a failing or misadjusted engine accessory belt and is accompanied by squealing that you’ve been vainly hoping will go away. Other possibilities include a budding electrical fire or a misrouted hose now resting against something hot.

Sour Mash

If the interior of your car is plagued with a vaguely sour smell, it’s likely you have some drains clogged. The drains, hidden under the opening at the base of the windshield or under the hood near the hood hinges, are regularly clogged with leaves and the like. Sometimes a garden hose with a high-pressure nozzle or a long screwdriver is enough to clear out the blockage. Once open, follow with a teaspoon of household bleach in a gallon of water to kill algae. Then flush that mixture out. Sometimes fixing air conditioner-related smells require professional help.

Your nose knows when there’s a problem with your car. Pay attention.