Dear Jim,

A few weeks back, I installed a new timing belt on my 1998 Toyota Tacoma (3.4L 5VZFE V6 engine, 94,000 miles). The car has been running well since then, but all of a sudden I'm hearing a rattle under the hood that wasn't there before I changed the belt. What do you think is causing this? The thing is, I'm sure everything got put back together the way it was, so I have no idea where this sound could be coming from.

--Brett Choi

Replacing the timing belt on an engine like yours is no easy task, bro. Even if you did put all the mechanical parts back the way they were, I'll bet dollars to doughnuts there's still one thing that's missing now: enough tension.

The timing belt itself has a "tensioner" device that uses your car's oil pressure to work right. If you replaced it, then that area is probably fine.

But there's also something called the harmonic balancer bolt in there, and it needs to be cranked on with a lot of torque (around 200 foot-pounds) for the system to work the way it's supposed to. That's quite a bit of energy, and you'll need to use a good torque wrench when tightening up that bolt -- not just one of those pneumatic wrenches. If that single bolt is too loose, the whole harmonic balancer and crank sprocket will shake back and forth while you drive, making that rattling sound you're hearing.

Basically, you're going to have to take everything apart again to get in there and correct the problem. Like I say, it's not so easy but you can definitely do it. And listen, bro, if you didn't do this already, make sure and replace not only the belt tensioner but the water pump and cam-shaft seal as well. They're both in the same area, they both tend to wear out after this many miles, and they're both pretty cheap to replace.

Tip of the Week

Speaking of water pumps, here's something simple everyone can do to help them last longer. Every 15,000 miles or so, buy a bottle of RMI-25 Cooling System Treatment and pour it into your radiator. Not only will it keep those pump seals lubricated, it'll also clean out the system, inhibit rust and mineral deposits, and generally make your engine run cooler. Those blazing summer days aren't so far away, folks.

Buffalo Jim, owner of Allstate Auto & Marine Repair in Las Vegas, writes a weekly column. Send your automotive questions to him at buffalojim@lasvegasniftynickel.com. If Jim picks your question to answer in Nuts & Bolts, you'll also be the proud recipient of a deck of official Buffalo Jim playing cards, presented in a classy, tin box bearing his hairy image.