Does your car's steering wheel jerk when you turn it? If so, and your car has power steering, you may be able to fix it yourself.

First check the belt that operates the power steering pump. If it is loose, this can cause the problem.Grasp the belt midway between the power steering pump pulley and another pulley. Move the belt up and down with your thumb and forefinger. It shouldn't move up and down more than half an inch.

If the belt is loose, tighten it. To tighten the belt, you loosen the alternator, idler pulley, or other component that is used to keep the proper tension on the belt. Let's say the alternaor is used to provide the proper tension on the belt. First you would loosen the bolts that hold the alternator tight. Then you would use a pry bar of some sort to pry the alternator out until the proper belt tension is achieved. Then retighten the bolts while holding the alternator in position.

When prying on the alternator, pry on a solid part of the alternator body. And be careful not to get any wires in between your pry bar and the alternator as you pry.

Also check the power steering pump to make sure its mounting bolts are not loose. If they are, tighten them. On some power steering pumps you may not be able to get at the mounting bolts with an ordinary wrench. You may need a ratchet, socket, extension, and possibly even a universal joint. If you don't have these, then have a garage mechanic tighten the bolts.

To see if the power steering pump is loose, simply grasp the pump firmly with both hands and try to move it back and forth. It should not move.

If the power steering pump is tight in its mountings, and the power steering pump belt isn't loose -- check the belt midway between the two pulleys. Twist it around with your fingers until you can see both edges and the underside. If these are glazed or oily, the belt should be replaced.

When buying a replacement belt, be sure to give the parts person at the auto parts supply store the year, make, model, engine size and type, and power-driven accessories (such as air-conditioning) that your car might have. That way you should get the right belt.

I say should, because parts people can occasionally make a mistake. So when you take the old belt off, match it up against the new one, to make sure it's the same size.

Replacing the belt may be easy, or not-so-easy -- depending on your car. If it's a four-cylinder engine with only one belt, with tension applied by the alternaor, then removal and replacement is a snap. Just loosen the bolts that hold the alternator in place, slide the alternator in some to relieve all the tension on the belt, then simply lift the belt off all the pulleys. Lift the old belt up between the fan and the radiator. And then slip the new belt on. Once it's in place, apply the proper tension with the alternator and tighten.

On larger engines with more than one belt, you may have to remove other belts in order to remove the belt you want (if that belt is at the back). So the job may take a little longer.

Also check the power steering fluid to make sure it is at the proper level. If it is low, add the power steering fluid recommended in your owner's manual until the power-steering pump dipstick indicates the fluid is at the proper level.

If the fluid level is okay in the pump, the belt is okay, and the pump is securely fastened -- and the steering wheel still jerks -- have a mechanic look at it.