Dear Tom and Ray: I have a 1998 Nissan Altima, and every time I put gas in the car, the nozzle clicks off, or the gas splashes back out like it's full. What is causing this? It is so irritating! I have to pump gas into the car slowly, then stop and wait, and then slowly pump some more. I have taken it to the dealer and they said they didn't find anything wrong with it. What do you think the problem is?

Lottie

Ray: I don't know, Lottie. I don't see any problem. Do you, Tom?

Tom: Of course there's a problem. We just got a letter from some poor bloke who must have pulled in behind you at the pumps. He complained that he had to stew for 10 minutes while waiting for "some gal in an Altima to figure out how to pump gas."

Ray: This condition is probably caused by either a blockage in your gasoline vapor recovery lines or a bad refueling control valve.

Tom: Gasoline vaporizes. How do we know that? Well, when gasoline is spilled, you can smell it, right? What you're smelling is vaporized gasoline.

Ray: And in the old days, when you filled up your tank, all the air inside the tank -- the air filled with gasoline vapors -- came whooshing out through the filler hole or through a vent at the top of the gas tank.

Tom: But then people in places like Los Angeles realized they couldn't see the person standing next to them due to smog. And since gasoline vapors contribute to smog, car makers were forced to install devices to capture those vapors.

Ray: So now each car has a vapor recovery unit that collects the gasoline vapors from the tank and then, the next time the car is started, sends them to the engine, where they're combusted. Your vapor recovery system isn't working, Lottie. One possibility is that one of the rubber hoses is blocked or collapsed.

Tom: Why does that keep you from filling your gas tank? Well, when the air (and the vapors) can't get out of the tank, there's no room for gasoline to go in.

Ray: The other possibility is that one of the valves involved in the refueling process (the refueling control valve, the refueling EVAP vapor-cut valve or the one-way fuel valve) is not working.

Tom: In any case, you should go back to your dealership -- or maybe find a different dealership that cares a little more -- and tell them there's a technical service bulletin that explains how to fix this. Have them look it up under "slow fuel fill."

Dear Tom and Ray: I have an ongoing "debate" with my hubby about whether to leave our car windows open slightly when it is really, really hot. One of us says we need to do this to keep the windows and windshield from cracking (especially if there is a drastic temperature change due, for example, to a thunderstorm). The other doesn't think it's necessary and prefers to leave them closed. So which do you recommend?

Barbara

Ray: Actually, there's no need to keep the windows ajar. The windows and windshield will not crack from the heat, nor from the sudden drop in temperature that often accompanies a thunderstorm. After all, if that were the case, your windows would crack every time you got into a hot car and cranked up the air conditioning, right?

Tom: So, if you don't mind getting into a hot car, you are free to leave all the windows closed.

Ray: If the heat is an issue for you, though, you have several options. One is to just open the windows a tiny bit to allow some hot air to escape Another is an old and sadly neglected remedy for extremely hot weather: Park in the shade.

Listen to "Car Talk" at 9 a.m. Saturdays and 5 p.m. Sundays on KRCU 90.9 FM -- Southeast Public Radio. Write to Tom and Ray at Car Talk Plaza, Box 3500 Harvard Square, Cambridge, Mass., 02238. Or e-mail them at the Car Talk section of cars.com.