Cars can be full of mysteries, especially if you’re not the first owner. What’s that smell? That noise? Why is it like this?

I’m not even talking about problems, necessarily, though those could be mysterious as well. The mystery that’s currently vexing me is definitely one of a mechanical nature, but truth be told I have no idea if it’s even really a problem. Could it be a problem? Maybe. Maybe not.

One of my cars is a 2002 Lexus IS300 Sportcross. It’s blue and it’s pretty and it’s wonderful, and I know I’m at least the third owner. Possibly the fourth. It’s hard to say, though it does appear to have been meticulously maintained by everyone involved. But even the best maintenance can’t entirely prevent some issues.

The case of my Lexus revolves around the notion that the 2JZ-GE inline-six-cylinder engine is, fundamentally, what is known as an “interference engine.” That means that when its valves are fully extended, they move into the area of the cylinder that’s normally occupied by the cylinder when it’s at its full height. Normally, that’s not a problem whatsoever, as there’s a trusty timing belt that makes sure that everything is at the right place when it’s supposed to be, and not in the wrong place when it’s not.

If the timing belt were to suddenly disappear, there’s a good chance you’d get pistons smacking into valves, and that is not a good thing to have. There’d be a lot of repair work involved, to keep it short.

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To make sure that everything stays peachy under the hood, Lexus recommends you swap the timing belt every 90,000 miles, or eight years, whichever comes first. Old rubber cracks and can eventually snap, you see, so it’s best to just keep it nice and fresh.

Which brings me to my mystery. My car doesn’t have 90,000 miles on it yet, but it is 16-years-old. Looking under my hood, there’s a timing belt replacement cover, and the timing belt looks fine visually, but the replacement cover is also supposed to say the date and mileage it was replaced at.

But it doesn’t. It’s completely blank. Meaning I’ve got nothing to go on.

Was it replaced last year? Two years ago? Eight years ago? Ten years ago? Who knows.

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As much as I’d love to avoid the cost of getting a timing belt service done (about $275 if I do the work myself, about $1,000 if I get a mechanic to do it, which includes a new water pump and whatnot as you might as well while you’re in there), I might not have a choice. Maybe I have to get it done soon. Maybe I have to get it done right now. Maybe I don’t have to get it done for another five years.

It’s a complete mystery.

I’ll probably end up doing it at some point over the next couple of weeks just to be on the safe side, but even still, it’d be nice to know what the deal is.

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What mysteries does your car have?