When driving down the freeway, I heard a scraping sound, shortly followed by my car slowing down, no matter how hard I pushed on the gas. I barely made it to the service road without getting hit by other traffic. When the tow truck driver came, he noticed green liquid (coolant) leaking out. The mechanic towed the car and said my water pump had frozen, and that broke my timing belt. He said it was the first time he had ever seen it, and he doesn't know of a way I could have avoided it. I need to know if it was something I did, that I can avoid doing in the future. I am paranoid about the situation and worried that it will happen again. Thanks!

RAY: It does happen. But we like when it happens. For us, it means we won't have any trouble making our boat payment that month!

TOM: You don't tell us what kind of car you drive, but I'm guessing it's something with a non-interference engine. Cars with interference-style engines get ruined when their timing belts break. It sounds like you were lucky and you avoided that grisly fate; you got off with just an expensive repair and a severe travel disruption!

RAY: The vast majority of manufacturers recommend that you change your car's timing belt after a certain number of miles - 60,000 miles used to be common. Now lots of manufacturers suggest 90,000.

TOM: If you don't change the timing belt, it can break on its own due to age and use. But on almost every car we see, the timing belt also runs the water pump (which circulates coolant in the engine). In other words, the timing belt goes around a water-pump pulley, and as the belt turns, it makes the water pump's impeller spin. But if the water pump fails and seizes up, like yours did, it takes the timing belt with it.

RAY: So to prevent this in the future, you have to do a better job of maintaining your car.

TOM: For instance, it's possible your water pump was failing and you just didn't notice the horrible growling sound coming from your engine compartment. Or you don't see a mechanic regularly, so no one else had a chance to notice it.

RAY: Or maybe you were a good car owner, and you had your timing belt changed when it was supposed to be, but to save a little money, you or your mechanic didn't change the water pump at the same time. That's penny-wise and thousand-dollar foolish, in our opinion.

TOM: Yeah. We'd never change a customer's timing belt without changing the water pump, too, for the very reason that caused you to write to us - that's what can happen. And then they come back and blame us for it!

RAY: Also, we tend to use factory water pumps rather than aftermarket pumps for this repair, because the risks, if the water pump fails, are so severe.

TOM: So, how do you prevent this in the future? Get better about your regular maintenance. Find a mechanic you trust (if you don't already have one, find one at the Mechanics Files at cartalk.com). And take your car in on a regular basis. Even if it's just for an oil-and-filter change every six months, at least someone has a chance to notice when something is going terribly wrong.

RAY: And spend a cozy evening curling up with your owner's manual (that's the thing that's still wrapped in cellophane in your glove box). Read the maintenance section, and see what sorts of things are required at different mileage intervals. A good mechanic can help you determine which items are absolutely necessary. But here's a hint: Changing the timing belt and water pump is one of them! Good luck.

How does one change the key fob battery in a 2003 Volkswagen Jetta Sportwagen TDI? Does the remote require a special process in order to be recognized by the Jetta after you're done? Cheers!

TOM: No, it's a piece of cake.

RAY: You probably have the old-style, "switchblade" key fob with a blue VW logo and three buttons on it (lock, unlock and trunk).

TOM: Assuming that's the one you've got, all you do is press the button so the key springs out. Then turn it on its side. You should see a small groove about halfway up the side. Take a small flat-head screwdriver, insert the end in there and gently twist to pop open the two halves of the remote. Then pull them apart.

RAY: The section with the key will come off, and you'll see that there's nothing in it, other than the key.

TOM: But don't throw it away. You might want it later.

RAY: Then take the other half of the remote and, with your hands, separate the front from the back. One half will house the circuitboard, and the other half will contain the battery.

TOM: Pop the battery out gently with your screwdriver, and push in your replacement CR2032, 3-volt battery (positive end down), which you can get at any hardware or even drugstore.

RAY: Then snap the whole thing back together. It should require no reprogramming whatsoever.

TOM: If you bought a new remote - like my brother did last summer, after I went for a dip in the ocean with his remote in my pocket - that new remote would have to be matched up to your car.

RAY: And sometimes, with modern electronics, if you leave it without a battery for a long time, it can lose its programming memory. So don't start this process and pop out the old battery until you have a replacement handy.

TOM: But it's a trivial job. That's why my brother never charges his customers more than $475 to do it!

Got a question about cars? Write to Click and Clack in care of this newspaper, or email them by visiting the Car Talk website at www.cartalk.com.