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Step-by-step search is way to identify odd rattles

There's nothing more irritating than a car that squeaks, rattles, and rumbles every time it rolls. Such noises plague owners of new and old cars alike and, too often, they live with the problem rather than do something about it.

Certainly, most chassis-oriented noises can be detected and eliminated only by professionals with expensive equipment. Yet the most common noises that emanate from a car are produced by the body. And these noises can frequently be pinpointed and silenced by the owner himself.

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According to professional body repairmen, here's what you should know and do to put the muzzle on automotive body noise: Tune-in with a road test

To be intelligently analytical of unusual noises, you first need to know the normal sounds of your car.

When your engine is running at idle - in the driveway or parking lot - listen to it carefully from inside and outside the car, as well as with the hood open and with it closed. Also, take a run down the street and on the highway, paying close attention to the sounds of the car in motion with the windows rolled up and down.

Besides observing normal sounds, you'll learn how many deceptively unusual noises are actually the result of acceleration, deceleration, tire-to-road contact, suspension response, and other normal activities.

A similar road test should be taken when you first hear an unusual noise, provided the noise isn't too loud, of course. Loud noises are an obvious sign of serious problems, and continued driving may only enhance the noise, cause severe damage to your car, or both.

Call for a tow truck and seek a professional's advice when you encounter loud noises. Chassis or body noise?

The purpose of such a road test is to help you distinguish an unusual noise as coming from the chassis, body, or engine. The chassis is the part of the car that supports the body and consists of the frame, wheels, suspension system, and related machinery. If your car is new it may not have a conventional chassis.

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It's important to note that noise which occurs as the engine idles is normally caused by the chassis. For instance, a squeak or rattle can often be traced to a loose mounting bracket, pulley, or motor mount.

Similarly, a noise that occurs only at a steady speed range is usually the result of a chassis problem. Unbalanced wheels, for example, will cause the car to vibrate, thus causing rattles, at about 45 miles an hour.

It's also essential to recognize noises resulting from engine deficiencies. Carbon knocks, valve-tappet clatter, hydraulic-valve-lifter clicks, spark raps, and fan-belt squeal can be heard easily with the hood open or closed.

If the problem is one of these, you've solved the case. If not, it's time to move on to the body. Define the noise

Different kinds of noise have different causes. Thus, by knowing or defining the noise, you can check the most likely reasons for it. The rushing sound that wind makes is very different, for example, from a rattle.

If you can describe the noise as wind, you can proceed to check conditions that are known to produce the noise, such as a loose molding strip or worn window weatherstripping.

On the other hand, some noises are very close in sound, such as a squeak and a squeal or a rattle and a chatter. When this is the case, it's even more important for you to determine the frequency with which the noise occurs.

Here are the most common sounds, including a definition of each, which can be tracked to automotive body-related problems.

* Rattle - A rapid succession of short, sharp noises, which resembles the shaking or recurrent collisions of hard bodies. Noise occurs continuously, regardless of road and travel conditions.

* Squeak - A sharp, high-pitched, piercing noise occurring most frequently as the car goes over dips or bumps in the road.

* Rumble - A dull, nonrhythmic pounding occurring either very frequently at any speed or only when the car contacts a dip or bump in the road.

* Whisk, whish, or whoosh - A sound resulting from a swift, explosive rush of air. It is most noticeable at higher speeds. Out with the rattle

One of the most common and elusive noises is the rattle. Loose objects in the glove compartment or trunk could be the problem. Also check the exhaust system for looseness or wear, especially if the rattle seems to be coming from beneath the car.

In most cases, rattles attributed to the body are caused by nuts or bolts left in doors during manufacture, misaligned doors, worn window regulators, and loose windows.

Start at the side of the car where you hear the rattle. Tap the bottom area of the door with a rubber mallet. If the door rattles, the noise is undoubtedly caused by a loose object lying in the door well. Remove the trim panel to get to the object.

Next, grab hold of the door handle and swing the door out and in several times. If the door rattles or seems loose, it is probably misaligned. For confirmation, hold a piece of stiff material - a credit card, for instance - across the gap where the door meets the body.

Determine if the surfaces are flush and in line. A head-on examination of the chrome molding may also show ''unevenness'' of the molding strips - another indicator of poor door alignment. To correct the problem, check the owner's manual for instructions on how to adjust the door hinges; or have a garage or body shop do the job.

A misadjusted striker will cause the door to rattle, too. The door-striker-plate-to-lock distances will have to be checked to determine if the striker needs adjustment.

Clean off the striker and door lock and apply a little grease to the striker. Open and close the door a couple of times to create a pattern in the grease. If the impression of the lock's jaw in the grease is more than 5/32ds of an inch from the striker plate, adjustment is required.

Some strikers have to be unscrewed so that shims can be placed under them. Adjustment of other strikers is made by screwing the striker out or in.

Carefully tap the trim panel side of the door with a mallet. If you hear a rattle, the window regulator itself is loose or some of the parts are worn. Remove the trim panel to make repairs.

Now, hit each window gently. If it rattles or vibrates, the weatherstripping has probably worked loose or is worn.

In either case, pull the weatherstripping away from the window channel, wash the channel and the back side of the weatherstripping with kerosene, and apply a liberal coating of rubber cement to both surfaces. When the cement is tacky, press the weatherstripping firmly into the channel.

If you haven't found the source of the rattle at this point, see a professional, explain what you have checked, and ask him to check for any loose body bolts before moving on to make a chassis or engine inspection. Out with the squeak

Whether you call it a squeak, screech, or a squeal, a noise of this type is usually the result of loose, dry parts rubbing together. A bolt might become loose enough, for instance, to allow adjacent parts to make frequent contact with it.

Where the body is concerned, squeaks can most likely be traced to loose bolts that fasten the door, trunk lid, or hood to the car. Open and close these parts at a gradual, then faster, pace.

If the squeak turns up, apply a stick of stainless silicone lubricant to the main hinges. Then tighten the bolts with a socket wrench.If the squeak still persists when you drive the car, locate the following items and treat each with the lubricant recommended:

Door strikers, a stick lubricant; window channels, aerosol silicone lube; door lock and speedometer cable, graphite lubricant; hood latch, grease; fender skirts, silicone lube; and pedal linkages, aerosol silicone lube. Where necessary and practical, tighten these parts for more permanent silencing.

As a final measure to get rid of the squeaks, see a professional for a complete chassis lubrication, including under-the-hood engine units. In the service process he will even be able to detect such items as worn bushings, shackles, or shocks that could be the real cause of the problem.

Out with the rumble

Depending on the degree of looseness, those hood, door, and trunk-lid attachments could also be the cause of rumbles. Perform the measures specified in ''Out with the squeak,'' but if this doesn't solve the problem, go ahead with the following:

Check under the hood for missing rubber or fabric anti-rattlers. If these are intact, check the hood fastener for insufficient spring tension. In most cars, tension can be adjusted by loosening a lock nut, turning the dowel inward with a screwdriver, and retightening the nut.

Also check for a misaligned hood. Usually, elongated holes at hood hinges permit fore-and-aft movement of the hood-hinge bracket. To align the hood, loosen the hinge-adjusting screws, grasp the front of the hood, and shift it around until it is centered. Then carefully raise the hood and tighten the hinge screws.

If the rumble is coming from the rear of the car, minor adjustments might be necessary on the hinge or locking mechanisms of the trunk lid. First, make sure that the noise isn't coming from a loose spare tire.

To find out if a trunk-lid adjustment is necessary, chalk the edge of the body flange with white chalk and close the lid. If chalk marks on the weatherstripping are not visible all around, adjustment is necessary.

Out with the whooshWind noise is a common problem because of the popularity of molding strips on today's automobiles. If a molding is not tight, wind rushes between the body and strip, thus creating a whooshing sound.

To track down a loose molding, place tape over one strip at a time and road-test the car. When you no longer hear the noise, you have found your noisemaker. Remove the strip, apply automotive caulking compound to the back, and reattach the molding to the car.

If a loose molding is not at fault, check each window and door, using the same method. Tape the cracks around one window or door at a time and then road-test the car.

When the noise ceases, replace or reseal the weatherstripping of the offending door or window.

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