Diagnosing Car Odors and Leaks

Cars are marvelous inventions. Where else can you find such an intricate mesh of features and working parts, all engineered to get you where you want to be and do so while relieving you of the maximum amount of money possible?

OK, the federal government does NOT count.

All joking aside, though, your vehicle is probably one of the items in your household you rely most upon. So when a funny odor makes itself known, or you see a suspicious drip under your car, don’t automatically assume that the odor is the result of too much cheese and the drips are from your neighbor’s fountain pen. Diagnosing these signs may let you catch critical problems before they become really expensive.


Most smells are characteristic of a fluid that is leaking or spraying into a hot area, such as the car’s engine. A quick listing of some of the more common odors of a troubled vehicle is presented below, along with the most likely culprit:

Odor #1: A sweet smell, like hot syrup
Culprit: Most likely the antifreeze or coolant from your radiator. If you smell the odor alone, chances are that you have a slow leak in the overflow pipe or tank for the radiator. If accompanied by steam from under the hood, there may be a much more serious problem.

Odor #2: A thick or choking odor, like burning diesel fuel
Culprit: An oil leak. This odor is usually caused by oil leaking into the carburetor. It may be accompanied by smoke, usually bluish-white, from the tailpipe.

Odor #3: Hot, metallic odor, like a frying pan that’s been on the stove for a long time
Culprit: Overheating engine. May be accompanied by the sweet odor of burning coolant.

Odor #4: A thick stench like burning rubber
Culprit: Your brakes or clutch, especially if you’ve just come down off a winding or twisting mountain road and have had to use either or both for a while.

Odor #5: An acrid odor similar to burned bread
Culprit: A short in your electrical system. The odor is coming from the scorched insulation.

Odor #6: A sulfurous smell, like rotten eggs
Culprit: Your emission system. The odor is caused by the failure of your converter to remove sulfide compounds from your exhaust.


If you’re wondering what the stains under your vehicle are from, slide a clean piece of cardboard or poster board under you vehicle and leave it there overnight. In the morning, take a look at the color and the consistency of the stain and compare to the following chart:

Stain #1: Black, with thick or heavy consistency, like sandy shortening
Culprit: Axle leak, generally grease

Stain #2: Brownish stains, usually thin consistency like salad oil
Culprit: Oil or power steering fluid leak

Stain #3: Reddish stains, consistency or salad oil
Culprit: Transmission fluid

Stain #4: Greenish, yellowish or pink, consistency of juice, sweet odor
Culprit: Radiator leak, symptoms are of antifreeze/coolant

Once you’ve diagnosed the basic issue at hand, call your mechanic and talk with him or her about what you’ve seen. If necessary, be prepared for a (hopefully) quick visit to the shop. Good luck!

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