Washing the car led to water up the tailpipe.

Dear Car Talk

Dear Car Talk | Jan 01, 2002

Dear Tom and Ray:

Yesterday, during my biannual car washing, my 5-year-old squirted water up the tailpipe. I did not see her do this, but I was alerted when she came around to the front and asked "Would it be OK to get that hole wet?" At my request for a re-enactment -- without the water -- she said she put the hose nozzle up to the pipe and squeezed with both hands and "Whoooosh! I did it a lot of times." I have a '95 Mazda 626 with 150,000 miles, and it's the "good" car. Am I in trouble? I haven't driven it since then except for a 10-minute drive. I have a 40-mile commute tomorrow. Please advise. -- Judy

TOM: Don't worry about a thing, Judy. Since the car started, it's absolutely fine.

RAY: If you put enough water in there, I suppose it's possible to block the exhaust from coming out. Then you'd have the equivalent of a potato in the tailpipe, and the car wouldn't start. But that's tough to do, even for a determined 5-year-old.

TOM: So what you had was a bunch of water in the tailpipe and muffler. And what happened is that when you started the car, the pressure in the exhaust system pushed most of it out, and the rest was vaporized by the heat and then sent out the tailpipe. The exhaust system gets up to several hundred degrees Fahrenheit when the motor's running. And that's enough to vaporize any remaining water in very short order.

RAY: If you had let the water sit in there for a week, that might have led to premature rusting of the muffler and tailpipe. But since you drove it right away, I don't think you have to worry at all.

TOM: And water is not a foreign substance in there, Judy. Water is one of the byproducts of a gasoline engine. So the exhaust system knows just what to do with this stuff. Tell your daughter that, next time, if she really wants you to spend more time at home with her, she needs to pack a bunch of pancake mix in there before adding the water.

Get the Car Talk Newsletter

Got a question about your car?

Ask Someone Who Owns One