Pre-Purchase Inspection

Since C4 production stopped in 1996, any purchase made will be of a used automobile whose condition should always be assumed to be suspect.

Because of the mystique of the CorvetteŠ in general and the drop dead good looks of the C4 in particular, it is easy to get caught up in the moment and find yourself the owner of a fiberglass basket case.

Although it isn't possible to list everything you should check there are some general guidelines that you should follow whenever you plan on purchasing one of these wonderful automobiles.


The very best defense against buying a carload of trouble is to ask for the service records.  If the automobile has had only one or two owners, you may be able to get the entire history in this manner however, even if there has been a whole host of owners, the last owner should have kept the receipts from the present service history and if he or she cannot or will not produce them, it is a red flag.

All GM dealers conduct their business via computers and if you approach a dealer to do a pre-purchase inspection of the automobile, you may be able to persuade them to print out any records related to the VIN number.  Although these records are purged from time to time, it is worth asking.

Finally, if the selling individual will disclose the shop or dealer which has been maintaining the automobile while they have owned it,  you can approach them with your questions should the seller be unable or unwilling to produce records or receipts which clearly identify the automobile in question.

If there are no records and no leads on who has been maintaining the automobile, you will either have to thoroughly check everything on the vehicle or walk away from the potential purchase. 

Often, since the seller will seldom pick up any costs associated with a pre-purchase inspection, walking away may be the best idea in these cases.

Still, lets be optimistic and assume you have found what appears to be a low to moderate mileage C4 that appears to be in good shape.  What to look for in that situation is the question.


Every dealer, every person selling an automobile, everyone who hasn't spent the last 100 years off the planet knows it is the appearance of an automobile that first gets a potential buyer's attention and if the visual pleasure is great enough, the buyer can be rendered unconscious to the defects present in the automobile.

This is particularly true in the case of the Corvette.

What to look for

Normally, a savvy seller will have the automobile "detailed" prior to placing it on the market.

A detail shop will steam clean the engine compartment, apply a top coat of Armor AllŽ or another of the wax based interior products to the dash,  seats (if leather or vinyl) and all plastic trim.

The shop will thoroughly wash and  wax the exterior with a high gloss wax and apply Armor All to the tires.

Recently, Blue CoralŽ and Dupli-ColorŽ have teamed up to produce Dupli-Color Color Wax which hides swirl marks and minor scratches in the finish and detailers are using that product as well to make the appearance as pleasing as possible.

A prospective buyer should look at the exterior finish in bright sunlight.  Although the vehicle has been detailed, you will be able to pick up subtle clues that there are scratches and paint problems hidden under the wax if you examine the surface carefully.

Another trick is to apply Armor All to the actual paint. This technique hides problems with chipped clear coat and will make the front of the C4 in particular---where stone chips take a heavy toll---look better than it actually is.

You will also want to look carefully at all the weather strip material on the car.  It is almost a certainty that some of it will be cracked but if all the strips are in bad shape, it will cost you several hundred dollars to replace everything even if you do the work yourself.

Inside the automobile

Look for areas of wear in the carpet.

A common trick is to apply flat finish matching paint (particularly if the carpet is black) to areas where the carpet has been been worn through to the car's body.  Unless you look closely, you will think the carpet is in great shape until you purchase the vehicle and later notice you were tricked.

By the same token, if you observe new floor mats, be sure to look under them for signs of wear.

In the rear cargo compartment, look for cracked or damaged trim, broken or damaged top hold down hardware and scratched or otherwise damaged plastic seat backs.

Finding these situations and pointing them out to the seller along with protestations that you will have to have the car restored will sometimes result in a lower price.

Damage History

Many Corvettes have some damage history.  Most is very minor but occasionally you run into some major problems usually caused by an accident.   Before you spend your money, take the time to make sure you are not buying something that until recently was in a body shop or worse a junk yard.

Fiberglass Repairs

Unless a fiberglass panel has been actually replaced, it is relatively easy to determine if repairs have been made.

On the side of the panel away from the side normally viewed, look for a built up area where the resin and fiber have been applied to repair the damage.

Look at the underside of fenders, the inside of doors and inside the engine compartment.

In the rear, take off the license plate and using a mirror and a flashlight, look at the rear of the automobile for damage.

When a fiberglass repair is made,  the area is reinforced with fiberglass material and often stiffeners or doublers are installed to make the repaired area strong.   You should never see bulges or areas where the underside of the fiberglass is raged appearing and thicker than normal unless a repair has been made.

Symmetrical built up areas are acceptable if they are obviously part of the fiberglass structure formed when it was originally laid up.  These areas will be smooth and very commercial in appearance.  There will be nothing ragged about them nor will they appear to have occurred recently.

Frame Repairs

Frame repairs normally show heat discoloration or slight wrinkles where the metal has been reformed.

While the car is on a lift, look closely at all of the frame structure and supports for any sign of heat treatment or wrinkling.

While you might tolerate a little fiberglass repair you should never buy a Corvette that shows frame damage.  Unless the repair is perfect, uneven tire wear, poor cornering, pulling to one side and even life threatening situations are all possibilities.  It isn't worth it.

Visual Inspection

You will want to climb into the cockpit and take the automobile for a spin right away but wait a bit on that.  If there are serious problems present, why bother?

First go to where the car is located, do not allow the car to be brought to you.  The reason:  you want to see how the engine starts when it is cold.

After you have performed the visual checks of the appearance items, you will want to take a look at a few areas.  Here are some things to check:

Replace the air filter cover and ask the owner/dealer to start the engine while you watch.

If the engine is slow to start or the owner/dealer "helps" it, there may be hidden engine problems. A knocking sound that continues for more than just a second indicates rod bearing/lower end problems and is potentially very serious and expensive to repair.

When the engine starts, ask the owner/dealer to immediately turn it off and reposition yourself to the rear of the vehicle.  Wait one minute and then ask the owner/dealer to restart the engine while you watch for any sign of smoke from the exhaust. (If it is a cool or cold day, do not confuse condensation with oil smoke.  Condensation will be odorless, oil smoke will not).

Oil smoke normally indicates problems with either the piston rings, the valve guides or both.

Allow the engine to idle for a full three minutes after which time it should be running smoothly unless the ambient temperature is very cold in which case you may have to wait as long as five to seven minutes.

When the engine has warmed up, pull the PCV valve (the hose on the left side of the engine going into the valve cover) and make sure very little oil smoke comes out the hole where the PCV valve formerly was located.  A very small amount is OK but none if what you want and any more than a tiny amount indicates cylinder/valve guide problems.   

After the engine idle is as smooth as you feel it will get, place your hand near one of the two exhaust pipe outlets and feel for a smooth, almost continuous pressure.  You are doing an elementary test for a weak cylinder. and if you can detect instances where the pressure varies here, there is at least one cylinder with very low compression indeed.

Again ask the owner/dealer to shut off the engine and then immediately restart it.

It should start immediately and there should be no sign of oil smoke at the instant it "catches" or again, there may be piston ring/valve guide problems present.

Additional Mechanical Issues

Leaving the engine run, exchange places with the owner/dealer and perform the following checks from the cockpit:

NOTE:  All references to the LCD, Digital Dash or Electronic Instrument Panel, apply only to the 1984-1989 models of the C4 Corvette.  1990 and later have a traditional instrument gauges plus a LCD speedometer display.

Drivability Issues

Obey all traffic laws and do not endanger yourself, anyone else or any property as you perform the following tests:

Final Checks

Drive the vehicle to a service station with a lift and once the car is elevated on the lift, inspect the underside as follows:


If the vehicle passes these checks, depending on age you may wish to have a cylinder compression test performed.  If you are suspicious by nature, you may also wish to make sure that the serial numbers match and that the car has not been modified for speed contests in any manner.  These checks are best made by a professional repair shop or GM dealer.

A car that passes the tests above would appear to be in reasonable mechanical condition but the one thing you always have to remember is "If the car is perfect, why is the owner getting rid of it or why did the previous owner trade it in to the dealer?"

In other words, you can almost certainly expect to spend money on a used car when you purchase it!