Liquid trail

I noticed liquid coming from the tailpipe of my wife’s 2002 Altima as she drove away after she dropped me off at work today. The car had been driven for about 20 minutes before(10 miles), and the weather wasn’t bad - about 30 degrees. Is it worth a worry?

Most likely just normal condensation. I wouldn’t worry about it.

Check your coolant level and you’ll know fairly quickly whether to be worried or not. Was it blowing any white smoke?

No smoke; just dripping for a moment or so then stopped. What would coolant level have to do with it? Cylinder head gaskets no good? 73,000 K on car. I’ve had it since new.

The next time you see the liquid out the tailpipe, reach down and place the tip of your finger in the liquid, smell it and check if it has a smell. Rub it between your fingers to check if it has an oily feel. If not it’s probably just water from the catalyst proccess.

But the last test is to taste it.


All combustion produces water. If a car is idling for a while, some of the water condenses in the cooler parts of the exhaust system. When you drive off, it spills out the tailpipe. Totally normal. Take a look at the tailpipe of the next parked car you see that pulls out. If however, water is continually spilling out and you’re leaving a wall of fog everywhere you go, you might have a problem there.

OK. Thanks to all. Will follow up with all the suggestions.

The last test is to taste it ? No thanks, that could be YOUR last test. Though I and many have done it in the past, it ain’t the healthiest thing to do. Smelling is the best you’ll get from this side now.

Doctors also used to taste urine to diagnose diabetes. How times have changed…

If it is water, it is a byproduct of what the catalytic converter does.

Well, the cat puts out a little extra water from burning whatever didn’t burn in the cylinder, but the main source of the water is from burning the hydrogen in the gasoline, 99% of which occurs in the cylinder.

Gasoline is a hydrocarbon (HC), hydrogen atoms bonded to carbon atoms. Air is 22% oxygen. The engine mixes them in a proportion of roughly 15 parts air to 1 part hydrocarbon. The combustion process then causes the hydrocarbon to seperate into hydrogen and carbon, each finding oxygen atoms to bond to.

The primary byproducts of this splitting and bonding become carbon dioxide (CO2) and water (H2O). Additional byproducts, those from imperfect and/or incomplete combustion, are carbon monoxide (CO), oxides of nitrogen (NOx), carbon, oxygen, and a few miscellaneous products.

The water the engine produces is normally carried out by the hot exhaust, but when the exhaust has to travel through a cold exhaust system, it condenses on the inside of the pipe and even condeses into a cloud. Water dripping out of the tailpipe is the normal result.

Think about the math. 1/2 of every gallon of gasoline is hydrogen. It’s sprayed into air in a rough ratio of 15 gallons of air for every gallon of gas. If 1/2 of every gallon of gasoline is hydrogen, and most of it finds oxygen to bond to, producing H2O, than for every gallon of gas you burn the engine produces roughly 3/4 of a gallon of water. The engine is actually a water making machine.

The cat converter has nothing to do with it. Sorry guys.

MB is right. I’ve known this since I was a youngster in HS. We did tests as part of our normal studies. I was very interested in the subject, and it made a lasting impression on me. The perfect combustion process produces…air, and … water.

I also agree with Tester, taste IS the final test. You can laugh if you want, but whether it’s on the ground, in the tailpipe, or even sitting on the motor, you can tell what it is with taste. Notice I did NOT say to swallow any of the stuff, but your tongue is a very sensitive instrument, much more so than your finger, and you can use it to your best advantage…should you choose to have every weapon in your arsenal available.

Maybe feed that water to the barky dog next door? If he lives, it was just water?

Interesting comment about your toung being a tool. I agree. And if it IS something other than water, it won’t harm you just tasting it. Lord knows most of us have had a mouthful of gas and a faceful of oil once or twice…

But no need, really - if the smoking and dripping stop when it’s warmed up, it’s normal water.

Perhaps…but if it’s cold enough out and/or the trip is short enough it may keep dripping even after the engine has reached full operating temp. That’s common in the winter up here in NH.

Where I live most intersections are very slippery, even when the rest of the street is bare. This is of course the result of cars idling at the lights and the water vapor laden exhaust gas condensing on the cold pavement.

The city counteracts this by spreading “pickle”, a mixture of sand, calcium chloride and salt, liberally at the intersections.

"Notice I did NOT say to swallow any of the stuff, but your tongue is a very sensitive instrument, much more so than your finger, "

ALL automobile fluids are toxic !
“Avoid contact with skin”; that’s the advice for used motor oil, coolant and brake fluid.
I guess the mouth in tasting has "no Skin"
Individual tolerant levels vary dramatically. Ask anyone with peanut allergy. It does not take ingestion to be problematic. So, I know my self and what I’ve gotten away with tasting car fluids…but that’s the reason I am not going to recommend it to others. I guess we all feel that everyone is the same…
Place fluid on white cardboard and check color and smell; that should be good enough.

Point well made.