Body problems do not have the potential for sudden inconvenience and expense that mechanical and electrical problems do. Still, body work is expensive and time-consuming. So, whether you're buying a used car just for transportation or as a personal image statement, a close examination of the body can tell you whether to continue your interest in a particular car.

Check for serious body damage.
Most of the cars made today use unit-body construction. In other words, there is no separate frame; the body itself is the load-bearing structure. Severe damage to the unit body, in the form of extensive body damage or serious rust, can mean that the car has a short life expectancy. Fortunately, a sharp eye can usually pick out all but the most skillful body work.

Keep in mind, though, that not all body damage is terminal. Most used cars are likely to have been involved in a minor "fender bender" at some point. As long as the basic body structure was not deformed, good repair work can restore a car to acceptable condition. In fact, minor body damage can be used as a bargaining point if you are still interested in buying after the rest of your check-out. The key is to weed out and avoid the cars with damage so extensive as to pose a safety hazard or limit the life expectancy of the car. So, look carefully. Anything suspicious should be noted for your expert to examine.

Beware of the clip.
The most drastic form of body repair is the so-called "clip," where the good front and rear halves of two wrecked cars are welded together. It may strain the credulity of some readers to state that this is a serious problem, but believe it. It happens more often than you would think possible. No matter how good the welding is, a car formed from two clips will never have the structural integrity of the original, single-piece unit body.

Clips are usually joined at one of two places: just in front of the windshield (at the firewall) or at the post behind the front door (known as the "B" pillar). The best places to look for evidence of a clip job are under the car or under the carpeting inside. Underneath, look for a seam running all the way across the car somewhere behind the front wheels or under the door post at the middle of the body. Inside the car, pull up the carpeting and look for the same thing. Fresh paint under the carpet is another sign. Because a clip is unlikely to retain the stiffness of an undamaged body, another good tip is to test for torsional rigidity. This is how you can do that: Drive one wheel up onto a curb at least four inches high, then open the doors. If any of the doors can't be easily opened because they are pinched by the body, it's a good tipoff that the car is a clip. If you see any evidence of a clip, don't look any further; walk away from that car.

Beware of pan damage, too.
The second worst type of damage is pan damage in which the unit body itself (as opposed to the fenders or doors, which are bolted on) was bent and then straightened. Evidence of a body pan that is no longer structurally sound can be found in misaligned body panels, particularly doors that "droop" when opened. Open each door slowly while watching the top of the door frame. If it drops more than 1/4-1/2 inch after it clears the lock pin, odds are the pan has been weakened by a crash.

Check for other types of body work.
"Spot" body damage can usually be noticed by sighting down the length of the car. Ripples, waves, differences in symmetry from one side of the car to the other and slightly misaligned body panels are all telltale signs of "cosmetic surgery." A small magnet can be used to detect the presence of body filler (affectionately called "plastic" or "bondo" in the trade) to cover a dent. The magnet will have noticeably less attraction over the plastic than on parts of the body with just steel under the paint . (Of course, this test doesn't apply to cars with nonmagnetic skins, such as fiberglass or aluminum.).

Paint is an excellent tip-off to the presence of auto body repair. Walk around the car carefully looking for mismatched paint. Unless a car has been completely repainted, the paint in an area that has had bodywork will look newer. With metallic paints, the pigmenting will look "off" at certain angles because aftermarket metallics rarely match factory applications.

Even if a car has been totally repainted, some evidence of body work will probably show up. The most common giveaway is overspray. This is a mist of paint that has drifted onto an area not intended to be painted and not properly masked off. Good places to look for overspray are at the ends of trim pieces, around the windshield and other glass frames, the bases of side mirrors, inside door jambs, under the hood and trunk lids around the edges, inside the wheelwells, and behind and to the sides of the grille.

Look for rust.
Rust is another villain to watch out for--not minor surface corrosion, which can be lightly sanded and touched up with a dab of paint, but serious, metal-devouring rust. Places where rust can lurk on a car are plentiful. Take the trouble to look everywhere for rust, because it can dramatically shorten the life of a car. And, just because a car was "rustproofed" doesn't mean it won't have any rust. Prime places to look for this insidious menace are:

• The wheel arches. Mud and salty slush tend build up there and hold moisture against the body, making for an ideal rust producing environment.
• The lower front fender behind the wheels. Again, mud and salty slush are prime culprits, combined with chipped paint from thrown rocks.
• The trunk and fender wells behind the rear wheels. Once again, mud and salty slush are prime culprits. Water leaks into the trunk, too, and will seek the lowest level--usually the spare tire well and the fender wells on each side. The standing water ferociously breeds rust.
• Around the windshield and rear window frames. Water has a way of seeping into these areas and it doesn't evaporate easily once there.
  
• Suspension points. On foreign cars especially, rust can occur at spring and shock absorber mounting points at both the front and rear wheels. Many a collector's car has been relegated to the junk heap because of this very expensive to repair form of body cancer.

The above are just some of the more common places to look, but don't take any place for granted in your search for serious rust. Have your expert search as well and if either of you find it, best look at another car.

Examine the tires.
While you're looking the body over, look at all four tires. They should all be the same brand and should show equal wear. Today's radial tires normally last 40,000 to 50,000 miles. If the odometer shows significantly lower mileage and the tires look new, it could be a sign that the odometer has been rolled back. If the tires are mismatched, it could be a symptom of suspension problems. You'll want your expert to check out any of these problems.