Auto Repair: Torque and Adjustable Wrenches

Adjustable wrench

Torque wrenches

A torque wrench (two types of which are shown in Figure 3-7) is designed to tighten a nut, bolt, or screw to an exact degree to avoid under-tightening or over-tightening things.

Figure 3-7: Dial torque wrench and deflecting beam torque wrench

If you're replacing a spark plug and you don't tighten it enough, it will work itself loose and fail to deliver a spark. If you over-tighten a spark plug, you can strip the threads or crack the plug. Similarly, parts that have gaskets can leak if the bolts that hold them aren't tightened enough. But if you overtighten the same bolts, the gaskets will be crushed, causing the fluid to leak anyway.

Most really good torque wrenches are expensive, but a cheaper one is good enough to serve your purposes. If you'd rather not spend the money until you're sure that you really like working on your vehicle, borrow a torque wrench just to get the feel of how tight a nut, bolt, or other part should be. Or you can just forget the whole thing — I've never used a torque wrench; I use common sense.

If you use a torque wrench, keep the following in mind (follow these tips when you're using any kind of wrench to tighten anything):

  • Grip a torque wrench well down the shaft (not up close to the dial), and operate it smoothly.
  • Tighten a series of nuts or bolts to the specified torque in the specified sequence, which will distribute the pressure evenly instead of in strictclockwise or counterclockwise order.
  • When tightening a series of bolts, tighten them all just until they're snug. Then go back and tighten them all a bit more. Then go back and tighten them all the way to the torque specifications. Doing so ensures that the entire part you're tightening is under even pressure, prevents leaky gaskets, and increases the life of the bolt and the part.
  • Before using a torque wrench, make sure that the nut or bolt turns freely so that the torque wrench gets a true reading of the proper nut tightness. You can use a lubricant such as WD-40 on the threads and run the nut up and down a few times to free it before using the torque wrench on it.

Adjustable wrenches

Figure 3-8: Adjustable wrench

An adjustable wrench, sometimes called a crescent wrench, is a useful addition to your toolbox (see Figure 3-8). You probably already have one in the house, and you can adjust the jaws to fit a variety of nuts and bolts simply by turning the wheel. I like the very small and medium sizes because they fit into tight spaces easily.

From Auto Repair for Dummies, copyright © 2009 by Wiley Publishing, Inc., Indianapolis, Indiana. Used by arrangement with John Wiley & Sons, Inc.

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