Q: Dear Tom and Ray:

Perhaps you can settle a discussion that my son and I had recently. When his car overheated, I suggested that he add water to his radiator, since the level was low and he needed to keep driving. He insisted that he had to drive the car to the auto parts store to get antifreeze because the radiator cap said "radiator coolant only." I told him that water is a radiator coolant, and that the cap was so labeled so that some idiot wouldn't put oil or transmission fluid in the radiator. If you prove me right, I'll send him a copy of the column. If not, he'll never know.

--Bob

A: RAY: Hope you've got a 33-cent stamp handy, Bob. You're absolutely right. Water is definitely a radiator coolant.

TOM: In fact, it was the first radiator coolant. If you watch "Ben Hur" carefully, before the big race you can see him pouring water into the radiator of his chariot.

RAY: Ideally, antifreeze (usually ethylene glycol) is added to the water in a 50-50 mixture. The combination has a higher boiling point and a lower freezing point than either of the two liquids individually.

TOM: But in an emergency, it's certainly better to have some coolant than no coolant. And in most cases the coolant level is low, not empty. So there's already some antifreeze in the radiator and you're merely changing the ratio.

RAY: So water is an absolutely acceptable way to top off your radiator if no antifreeze is available. And, in fact, we've taken questions from people who have used all kinds of water-like substances in emergencies. (We're still not sure about Mountain Dew.)

TOM: There was even a guy whose girlfriend persuaded him to stand on the bumper and, uh, contribute to the radiator.

RAY: It was unlikely he did any damage. But just to be on the safe side he should--of course--flush the system immediately.

Dear Tom and Ray:

Our relatively new Toyota 4Runner has us stumped. While checking the tires on a recent trip, I noticed a strange wear pattern on the two front tires. I had the tires rotated soon after that, and the strange wear was confirmed by the mechanic. The front tires are severely worn on the inside edge, extending approximately 3 inches toward the center of each tire. On top of that, it appears as though there is a "bumpity-bumpity-bumpity" pattern to the wear. We have had no other trouble with the SUV, and we are in no hurry to visit the dealer--warranty or not. Can you help us?

--Dennis

TOM: It could be any or all of the following, Dennis: bad alignment, bad wheel balance, bad shocks or el-cheapo tires.

RAY: And if I were you, I would take it to the dealer. While it may be something they insist you pay for (they may argue that you knocked off the alignment by driving the 4Runner over some buildings in your new-SUV zeal), there may be something actually wrong with the truck.

TOM: If I were a betting man, I'd guess that you have toe-in and camber problems (both alignment issues) or that the 4Runner came with real cheap original-equipment tires. And those would be things that you would have to pay to fix.

RAY: But if, for some unusual reason, the car can't be aligned (if there was a manufacturing defect, for instance), then the warranty would apply, and you'd certainly want the dealer to take care of it. Good luck.

Got a question about cars? Write to Click and Clack in care of this newspaper.