Avoid the DIY A/C Charge

So summer time is here and you are feeling the heat. When you get into your car that has been parked outside in the hot sun in can be 150 degrees in there, and if you just roll down the window it doesn’t really help. If it’s 90 degrees outside, that’s better than 150 but it’s not enough to stay comfortable. Blowing 90 degree air into your face does nothing to cool you down like 36 degree air from your air conditioning system.

So you decide to see what you need to do to fix your A/C system. When you go to any auto parts store or any retail store with an automotive section you will always find a can of stuff to put into you’re A/C system to charge it. They say this will fix your A/C right up, and you can roll along in comfort. What they are selling is refrigerant in a can. This is required to make a refrigeration system, such as your A/C, function.

The problem is, charging the A/C is not as easy as adding a quart of oil to the engine, not only that but there are several things that can go wrong with your A/C, and running low on refrigerant is only one of them. To go even further, even if low refrigerant level is the cause of your lack of A/C performance, how do know this low level isn’t caused by a big leak that will cause your new can of refrigerant to run out in two or three days?

Sometimes the A/C quits working because it is low on refrigerant, and sometimes there is not really any reparable leak. If the system has slowly gotten warmer and warmer over the years then the possibility of just giving it a charge to repair becomes very likely. If the system was working normally one day, and then quit working over the course of a day or two, then charging the system will do no good because the refrigerant will just leak right back out.

The only way to determine what your system needs is to have a professional check it out. They will be able to determine exactly what is causing the A/C to blow warm air. They can check for leaks, and fix anything that might be a problem. They can determine exactly how low the system might be and they can charge the system with the exact amount of refrigerant that is needed to make things work perfectly.

When you buy a can of refrigerant from the store to do-it-yourself, you need to have knowledge of exactly how refrigeration works, and exactly how your system is set up, or you might overcharge it. Overcharging the system will not only make it function improperly and blow warm air, but it can lead to major damage within the system that could cost thousands of dollars to repair. Without the correct tools, over charging is very easy to do.

Some cans of refrigerant will come with a gauge that is to be used to determine how much charge is needed. This gauge is insufficient and will not work well enough, even in the hands of a professional. A professional will use a manifold gauge set that contains a gauge for high side readings, and a gauge for low side readings. Both sides must be viewed in order to determine if the system is properly charged. Even if you had the proper gauge set, there are no magic numbers that you can shoot for on the gauges to say the system is now full. Pressures change based on many factors and a good deal of experience is needed to determine if the pressures are correct for the vehicle and for ambient conditions.

A typical A/C gauge set.

Another problem with doing this yourself is many of the products that you can buy to charge your A/C system are not what you want and will cause further problems. For example, some cans of refrigerant come with compressor oil mixed into the refrigerant. This is never needed for a recharge but half the cans sold at auto parts stores have oil in them. Adding too much oil will cause the system to function improperly.

Some of the cans of refrigerant have stop leak added to them so that if you have a leak, the stop leak will supposedly fix it. As if to say just add a can and you will be all fixed up. This is especially bad. Any stop leak in any form is bad, but A/C stop leak is the worst stuff in the world. If you have this in your A/C system it will ruin many of the components in the system if an A/C line ever has to be opened for system repair.

Once A/C stop leak is exposed to air it solidifies and ruins all that it touches. Some shops will run tests on your vehicle before doing A/C work just to look for stop leak. If they get it in their A/C service equipment it can ruin the equipment. They run the test and if it comes back positive they may tell you to take a hike.

Run away from anything like this

Rarely do I ever advocate against a car owner dabbling in auto repair and maintenance, because I think it is so empowering for the individual car owner to learn how to take care of things themselves, but with A/C system service things are different. With so many variables in A/C repair don’t take a chance on the DIY A/C charge. Leave this job to the professionals. In the end it may cost you less money than messing it up on your own and then having the professional fix your mistakes. 

Deceptive Lights: The Battery Light

Dash lights that mysteriously and randomly illuminate mean things. What they mean is almost never what you might assume and without a little bit of knowledge about what the intention of the engineer was that designed this light you may never be able to make a correct guess.

The battery light is one of these deceptive lights. This is the light that when illuminated, looks like a little car battery with two terminals with a plus and minus sign on each side. We call this light the battery light because it looks like a battery, but if you look up the real name in the owners manual it’s probably referred to as something like the “Charging System Indicator Light” or some such thing.

This light does not indicate that your battery is bad, nor does it really indicate anything related to battery condition or function. This light will illuminate when the vehicle’s charging system output drops below a predetermined voltage, usually somewhere in the neighborhood of 11 to 12 volts.

When you first turn the key on to start your car this light comes on because the charging system isn’t doing anything. The alternator will not put out any electricity until the engine is running, thus the light stays on. Once the engine starts the battery light should go out because the alternator is now doing its job, and charging system voltage is at normal levels.

Older cars used a circuit of opposing voltages to make this light come on. This means that voltage from the battery and voltage from the alternator meet from two directions at this light in the dash. As long as the alternator is working correctly neither one of the opposing voltages can flow through the light and cause it to illuminate. If the alternator output falls to something too low, the voltage from the battery will overcome the alternator output, voltage will flow through the light, and it will illuminate. Newer vehicles have computers that monitor alternator output and if it drops too low, the computer turns the light on.

If this light comes on while driving what is the best thing to do? Hopefully you can either get the car home, or to the mechanic in a timely manner. If this light comes on it means that charging system voltage is very low, perhaps nonexistent, and the only thing keeping electricity flowing to vital engine control systems is the battery. When the engine is running electricity is needed to power the fuel pump, produce a spark for combustion, and run the computer that controls everything. Once the battery is drained because the charging system isn’t functional the engine control systems shut down and the engine stalls.

The alternator is where all voltage in the electrical system
Originates when the engine is running.

So if this light comes on while driving you should do everything you can to conserve the electricity in the battery and get to someplace where you can have the car looked at by a mechanic. Shut off the radio and any other electrical devices that are not vital, rear defrost, air conditioning, blower fans. Turn off any unnecessary lights, but if it’s dark outside don’t turn all your lights off. A fully charged battery may last for about 75 miles of freeway driving if all unnecessary electric devices are shut off.

If your vehicle does stall it probably won’t crank when you try to restart. Don’t go and install new battery. If you have some jumper cables you can charge your battery from the charging system of another car. With the jumper cables hooked up between a good vehicle and a dead vehicle, let the good vehicle run for 20 or 30 minutes. This will put enough electricity back into the dead battery to start that vehicle and drive it for another 20 or 30 miles. This process can be repeated if as many times as needed to make it too safety, but every time you run a battery dead it shortens the life span of the battery.

So if you see the dreaded battery light, don’t plan on driving the vehicle anywhere except to the repair shop. Chances are you will need a new alternator, but it’s also possible that your alternator drive belt is very loose or has come off. Neither one of these things is the battery, but that’s what the light looks like. Don’t be deceived by this deceptive light.

Safety Recalls and Real Safety

When an auto manufacturer releases a new model to market there is usually no doubt about the fact that they bear a certain amount of liability when it comes to product performance and safety. Every car company selling any kind mainstream automobile spends a great deal of time and money on research and development of safety and quality.

No matter how careful any company might be, sometimes they come up with an automotive system, or part of a system, or some other function that becomes troublesome once the car hits the market. Sometimes this is related to poor design, but usually it is related to poor quality parts. Durability can be hard to predict, except that usually parts that don’t cost as much, are the ones that are likely to fail. Considering how much influence accountants have in determining the composition of the final product, manufactures will take some short cuts here and there in the name of fiscal responsibility, only to have that decision come back and bite them.

This seems like a serious issue and in many ways it is. The automobile is a big expensive machine that we rely on tremendously. When it’s working properly we routinely take it for granted. When it isn’t working properly, it will ruin our day and lead to frustration. At its worst the dysfunction of the automobile leads to injury and death. This end is much more common than we seem to remember.

The number of things that can go wrong with a car and cause massive failure is so great that perhaps it is best the auto driving public doesn’t really understand. Whether a car is well built, or poorly built, it is just a machine and it is perfectly capable of failing in spectacular ways at any moment, yet we continue to drive them without giving all things proper consideration. We even bring problems on ourselves when we let them run out of gas while driving in traffic. Should we sue people that run out of gas, or maybe have them hauled to jail for public endangerment?

As an experienced automotive technician I can think of many problems related to the design and function of many makes and models that cause them to fail regularly, and sometimes while in traffic. This is extremely common and sometimes the problems are much worse than an ignition switch going open circuit in the middle of the road. If an ignition switch fails you can still steer the car to the side of the road.

Some Volkswagen and Chrysler products have major front end problems that can cause the front suspension to come apart while driving down the road. This is extremely dangerous because you might very well lose control of the vehicle, not because you panic at the failure but because the vehicle becomes physically impossible to control. Some of these models were recalled and some were not, and some might not fail in this manner until they have well over 100k miles on them. Do we not care about failures that occur outside the warranty time frame? Do we not care about failures on high mileage vehicles because only poor people drive those pieces of junk? Where do we draw the line, if indeed one must be drawn.

Honda issued an ignition switch recall several years ago that included a few models built in the late 90’s. These ignition switches were doing the exact same thing the GM switches are doing. Nobody ever accused them of covering up the problem but the recall certainly wasn’t big enough because many vehicles built before, and after the particular years included in the recall had, and continue to have problems. I own one of the vehicles not included in the recall and one day while driving down the freeway the car stalled. I pulled over, jiggled the key switch a few times, and the car started. At my nearest convenience I replaced the switch. Is there a lawsuit in there somewhere?

How many cars are on the road right now with bad tires? The numbers are certainly very high, but even worse is the fact that many people who know their car has bad tires refuse to do anything about it. Many times the tires have gone bad due to owner neglect. This is not the fault of anyone with deep pockets, this is simply due to the fact that most people are not meticulous in their car care. Should we sue them? Should the highway patrol setup check points for tires and impound every car stopped that is thought to be running on dangerous tires? What if a tire doesn’t last as long as the manufacturer says it will? What if they claim that tire should be good for 40k miles but it wears out at 35k? We could go on and on looking at these kinds of failures but just the notion of such would be silly.

Never mind defects and breakdowns, even without these things most people have a much higher risk of suffering injury or death due to the careless actions of themselves or others on the road. We however, generally go about our day never really thinking about this with the proper perspective. How many near misses does the average driver experience every year? We literally come closer to death at these moments than we do at any other time in our lives. All we do to handle the situation is honk the horn, exercise our middle finger, and by the time we have made it to our destination we have somehow already forgotten that we almost died just then.

According to the National Highway Traffic Safety Administration (NHTSA) 35,561 people died in traffic accidents in 2012. The number of these deaths where alcohol was involved is 10,322. The number of people who died in a wreck where driver distraction was to blame was 3,328. The number of injuries from accidents related to distracted driving was about 421,000. That’s right, 400k+ end up visiting the emergency room because some moron was on Facebook in traffic.

Why are we so concerned about the possibility of 13 deaths related to ignition switches in the Chevy Cobalt when nearly half a million people were injured last year because we refuse to keep our eyes on the road? It’s almost as if we accept the occasional text message in heavy traffic, but if a car company builds a machine that isn’t perfect 100% of the time, someone must be sued!

How can we attack auto manufacturers when we lost over 10,000 people on our roads due to something as insidious and widespread as drunk driving? Where is the greater evil here? Most of us have known others who have driven drunk and there is not a single solitary instance where we could point to it being a good idea. I have always been completely floored while listening to the casual manner in which a friend or coworker talks about the times they drove drunk. Driving drunk is a mistake every time it occurs just like texting and driving. Once again, some perspective is in order.

Let’s also not forget all of the legal and political issues that surround this latest scandal involving General Motors. GM was owned in large part by the federal government during the time that the cover up is alleged to have happened. Before GM was scooped up by the feds they were legally a completely different company. The GM that put junk switches in their cars is not the same GM that exists today. So the problem here is that according to the law, New GM is not liable for the actions of Old GM, and the government of course answers to nobody. In the case of lost confidence in a private company, consumers can walk away from products they don’t trust anymore, but nobody can escape the government.

Companies such as general Motors with their current ignition switch fiasco, or Toyota with their gas pedal problems from a few years ago, must do everything they can to make sure their cars are safe and work well. We should have some level of confidence in any major auto manufacturer that they will build their products to the best of their abilities. To do otherwise would mean the end of their business, and the end of the jobs of the tens of thousands of individuals who work for them.

So far in 2014 we are on pace to see a record number of recalls from the auto industry. No company is immune. GM, Ford, Chrysler, Toyota, Honda, Nissan, Hyundai, and Volkswagen have all recently issued large recalls. These recalls have for the most part been voluntary, why? Because each company really doesn’t want to lose the trust of the consumer. The sooner they can head off a potential problem, the better off the consumer will be, and the better off the company will be.

The loss of human life is always tragic. When a company causes harm to anyone, they should be held accountable if gross negligence, or conspiracy to keep quiet can be proven. Justice will prevail in the end, and any individual or company that lets self-interest stand in the way of doing what’s right, will pay a price. Even if no inept regulatory agency was there to execute some kind of punishment for the offending company, the company always suffers more when people quit buying their product.

One way or another this will be sorted out. In the meantime, don’t let the media hype get to you. As the old saying goes, “If it bleeds it leads.” Also, the media will always shoot at a big target every time one is presented, GM is just the latest big target on the rotation.

Control Your Cruise

 

Modern cars go much further in preventing driver fatigue than the cars from years past. Anything the engineers can do to make the car more pleasant to drive is a good thing. One feature that does this very well but that has actually been around for a very long time is cruise control. This feature is not new but it has evolved tremendously and really doesn’t function at all like it used to.

The first cruise control systems used canister with a rubber diaphragm attached to a cable that would hold the throttle open when engine vacuum was applied to one side of the diaphragm. When the driver wanted to increase the set speed a vacuum solenoid would allow more vacuum in to act on the diaphragm. When the driver would hit the brake a valve attached to the brake pedal would let all the vacuum out and the throttle would snap shut.

Newer systems started using more electronic controls such as a small electric solenoid that could pull on a cable to hold the throttle open at the set speed. These systems looked at vehicle speed sensors to make sure they were accurately maintaining the set speed. A change in the set speed caused the electric solenoid to pull the throttle open more or allow it to close. When the driver hit the brake pedal an electronic switch would signal the actuator to release the throttle.

Electronic throttle control makes cruise control simpler.

Every car today whether it has cruise control or not is equipped with electronic throttle controls. The gas pedal is no longer attached to a cable that goes through the firewall to pull the throttle open. The gas pedal is attached to a sensor that tells a computer the driver wants more throttle. The computer then commands an electronic motor to open the throttle the requested amount.

Since there is a computer controlled actuator working the throttle, the only thing we need now to make cruise control work is a switch that tells the computer to hold the throttle open even when there is no foot on the gas. So the sensor attached to the gas pedal, and the buttons for the cruise control signal the same computer. This is a good example of computers simplifying the systems under the hood. A cruise control actuator and all the associated linkages are no longer needed.

This is not where the evolution of cruise control ends. Many cars are also now equipped with what is known as adaptive cruise control. This will not only hold the vehicle at a set speed but it will also reduce speed as needed to keep from getting too close to the vehicles in front of you that are traveling more slowly. The driver not only sets the cruising speed but they can also set the minimum following distance.

At the front of the car there is a sensor that uses lasers that bounce off the car in front of you to measure the distance between you and them. The computer will reduce the cruising speed as needed so you don’t get too close and once the car in front of you moves or speeds up the car will go back to the set cruising speed.

Adaptive cruise control won't let you get too close to the a slower car.

Adaptive cruise control is certainly one of those features that may cause us shake our heads in regards to the many new and somewhat silly features that we find on cars today, but of course this is where we are. In many ways these features that seem silly can actually make the car safer to drive by reducing driver fatigue and distraction. So while it seems that cruise control is the same as it ever was, it turns out it isn’t.  

Deceptive Lights: Check Engine Light

  

Everyone out there has probably had a car that had a check engine light come on at some point. Some of you might have even had one blink at you furiously. Sometimes, the illumination corresponds perfectly with the engine running rough, fuel economy falling into the basement, or the transmission shifting funny. Sometimes nothing seems different in the way the vehicle runs at all. Either way, anytime the light illuminates it means something is broken. However, when the check engine light illuminates, it probably doesn’t have anything to do with the engine itself. This can make the check engine light deceptive.

This little light of frustration and angst will illuminate anytime the engine control computer sees a failure in the powertrain controls that will cause an increase in vehicle emissions greater than 150% of the federal test standard. This means if something breaks and it causes your car to potentially pollute more than normal, the computer will turn the light on. Most of the time this failure is electronic in nature, and not mechanical.

The check engine light varies somewhat from one vehicle to another. Federal law dictates what it can be, but there are several options. The light must be amber (yellow-ish) in color. The light may say “Check Engine” or it might say “Service Engine Soon.” It may appear as a silhouette of an engine alone, or it make appear as a silhouette of an engine with the word “check” or a strange lightning bolt arrow in the middle.

Many old cars from the early days of computer controls may have used something completely different for the check engine light. On these old cars every manufacturer could do whatever they wanted when it came to this malfunction indicator lamp. Honestly, most cars back then were not smart enough to illuminate whatever they used for a check engine light when the vehicle experienced most failures, so the check engine light was not a very useful thing.

Federal laws regulating exactly what the check engine light should look like and exactly when and how it should illuminate didn’t become standardized until the 1996 model year. These new standards which are still in use today are known as OBDII. These standards came about to make things such as check engine lights simpler for vehicle drivers to understand, and to make the problems for which they illuminate easier for technicians to diagnose.

The most common failures that cause the check engine light to illuminate relate to the engine not running right at its most efficient. This inefficiency can cause rough running, stumbling, hesitation, lack of power, poor fuel economy, and of course increased emissions. Sometimes the engine will not seem to run any differently than normal, but this is not always perceptible to the driver, so if the light comes on it must be diagnosed.

Many times you will take your car into the shop to have the check engine light diagnosed and the technician may not be able to figure anything out right at that moment. Rather than educate you on the situation and the nuance of intermittent problem diagnosis, they may leave you with the impression that nothing is really wrong and sometimes lights like this just come and go. This is never true. If the light is really coming on for no reason it's because something is broken. If the light is coming on for a reason then something is broken. No matter how you slice it something is wrong. 

A scan tool that can be used to read diagnostic trouble
codes that caused the check engine light to come on.

Diagnosing an intermittent failure that causes the check engine light to illuminate can be difficult and can take time. Be patient with your mechanic and understand that the time they spend working on this issue should not some free. Their time is their livelihood and you must pay for it even if it seems as if progress comes slowly. You would be patient with a doctor trying to figure out a physical ailment so you ought to show the same patience with your mechanic, after all, he can't ask your car where it hurts.

The check engine light must also not be confused with service monitors. Many vehicles have systems that can monitor the time and mileage intervals that elapse between vehicle services such as oil changes and tire rotations. Some of these monitors are very sophisticated, and some of them simply count the miles for you. A service indicator might say something such as “Service Vehicle Soon” or you might see a small illuminated wrench. To make things more confusing the vehicle that uses the service vehicle soon indicator might also have a check engine light that says service engine soon. These are totally different but can be really confusing if your vehicle has both of them.

Consult the owner’s manual for a proper explanation of the maintenance monitors and the associated indicators. The manual will tell you how they work, and it will even tell you how to reset them most of the time. The check engine light on the other hand has no simple reset procedure. If it comes on, something must be repaired.

The one thing that is usually certain is that the illumination of the check engine light has nothing to do with the engine itself. Some people worry about the pistons and valves and other mechanical components of the engine when this light comes on, but most of the time these things are fine…most of the time. 

Monitoring the Thermostat

 

This is not that control panel on the wall of your house that you argue with your significant other over where the ideal setting should be. The thermostat is a control valve within the cooling system of your engine. Like the control panel for the furnace in your house, the engine thermostat is used to regulate temperature.

When the engine is cold the thermostat is closed, so coolant flow is restricted. This allows the coolant to heat up much more quickly because it cannot make its way out to the radiator where heat is released from the coolant into the outside air. The thermostat is located at the coolant outlet pipe coming from the engine going to the radiator.

Normal engine operating temperature is about 190 to 200 degrees F. Once the engine gets to a temperature close to this, the thermostat will open automatically. Most thermostats contain some kind of device that expands and contracts with temperature. When this thermally reactive unit gets hot it pulls the valve open allowing coolant to flow.

There are no fancy computer controls at work here, just old fashioned thermal expansion causing this thing to open. When the coolant gives off enough heat in the radiator to start bringing down engine temperature, the thermostat will react by closing slightly until the engine temperature is maintained at the optimum level for which it was designed.

Two problems result from a thermostat that has malfunctioned, but only one of them is well known because it leads to massive engine failure. The first and most dramatic thing that could happen when a thermostat goes bad is overheating. A bad thermostat can cause this when it simply fails to open at the proper temperature, or it gets stuck while opening and fails to open all the way.

When the engine overheats, the coolant heats up way past 190° to a point where the expansion of the various metal parts of the engine cause the parts themselves to fail. An engine can run safely up to about 230° F with no problems. When the temperature gets much above that the coolant can boil. Once the coolant boils it will build very high pressure in the cooling system and will boil over past the radiator cap or through the coolant expansion tank. This is why you see steam coming from some cars broken down by the side of the road. If temperatures get up to about 250° F the possibility for engine damage becomes a reality. Parts get weak and cylinder pressures go through the roof, literally.

The other thermostat failure that is not as well known but is probably just as common is overcooling. This is of course the opposite of overheating. Instead of the thermostat being stuck closed, overcooling happens when the thermostat is stuck open. If the engine is not allowed to warm up with the thermostat blocking coolant flow, it might not reach operating temperature at all.

Overcooling does not lead to a dramatic meltdown of expensive engine parts, which is why it goes undetected so much of the time, but it is still a problem that should be fixed. When an engine does not reach operating temperature it will not be able to maintain the correct air/fuel ratio. It will run rich, or with too much fuel. This is going to have an impact on fuel economy, but it will also have an impact on how much power the engine produces, and how much pollution will come from the tailpipe.

A typical engine that suffers from a thermostat that is stuck open might run as cold as 140° F. This might not seem that cold but it is. At this temperature you likely will not see your engine temperature gauge move very high off the lowest readings. In addition to this your heater performance will most certainly suffer. On those cold days when ambient temperatures are below 0, your engine will never come close to heating up, and you will probably have frost develop on the inside of the windshield.

Diagnosing a bad thermostat is no problem for an experienced technician. Many times a good repair shop will also recommend thermostat replacement anytime any work is done on the engine near the thermostat, regardless of whether or not it is currently known to be bad. Thermostats commonly go bad at inconvenient times, and considering it’s a $10 part, you should have it replaced anytime your mechanic is in the area.

Keeping the thermostat working will keep your engine running better, keep your fuel economy and power output up. And keep you from suffering a major breakdown from overheating in the middle of nowhere. Don’t forget about your thermostat, it would be a shame for a $10 part to cause so much grief. 

Used Car Drowning

 

Buying a used car off the lot or even from a private seller is never a comfortable thing for most people. The last thing you want to do is spend a hefty chunk of change on a new ride, and then have to spend a pile more on repairing some kind of hidden, preexisting condition.

One major problem that really does exist is a used car that has been in a flood. A car that has been underwater is a car that could have some very extensive problems. These cars come from places where some kind of natural disaster has occurred that has submerged hundreds or perhaps thousands of cars at once. Hurricanes such as Katrina or Sandy are prime examples of storms that have decimated the automobile population in their respective areas.

Insurance companies pay out millions in claims to compensate the owners of these vehicles. The cars are then sold as totaled vehicles and given special salvage title status. Sometimes in the shuffle of moving this metal away from the scene, the insurance companies sell them to third parties that do everything from scrap them, to fix them and return them to the road.

A certain portion will get into the auto auction circuit where they will be sold as a running vehicle but it will carry the salvage title status. Some may have lost their salvage title status when they were transported across the country from state to state. Some may be damaged in a flood but they never receive the salvage title status because the insurance company paid out to fix it, rather than replace it. If the car is repaired that doesn't mean that it's as good as new.

With a flood car the potential for severe damage is huge, and that potential exists for every part or system within the vehicle. If water is in the engine for just a few days it can cause rust which may either result in immediate problems, leading to immediate engine failure, or it may result in premature engine failure over a longer period of time. Just enough time for someone to buy it thinking everything is fine.

Corrosion on the terminals of an electronic sensor.

Electronic systems are extremely susceptible to flood damage. Every car on the road has so much wiring and so many computer controlled systems that it is impossible for a flood car to escape electrical damage. Corrosion in electrical connectors or computerized control modules is extremely difficult and expensive to repair. Many electronic failures that result from flood damage might not show up for years after the car has been returned to service. You might say that water damage does not necessarily destroy the car right away so much as it causes the car to lose years off of its usable life.

Besides things such as a Carfax report, the way to tell if a car has been in a flood is to look for obvious things that you don’t see on any normal car. Look under the seats at the seat tracks for rust or corrosion. Nothing inside a car should ever show the least sign of rust. Look in the trunk where the spare tire is located for similar rust and corrosion. The spare tire well may end up holding water for several weeks after the flood. Hidden areas underneath carpet or the dash are great places to look for water damage. 

Rust on metal parts that are not exposed to the elements is not normal, water damage in the carpets and seats may show as water stains or even signs of mildew might be visible, especially if you live in a place that is humid. Even in very dry places water can stay trapped inside headlight and taillight assemblies forever. Sometimes moisture or condensation will appear behind an instrument cluster lens. Many times if the water does eventually dry out it may leave behind strange residues in places where you should never see them.

Under the hood, take a moment to disconnect some of the electrical connectors that you find. These connectors are weather resistant but they are not exactly water proof. When submerged they will fill up with water and all of the pins will corrode. If you see any scale buildup, or if the pins are anything other than shiny and new looking, then they have been wet.

Some used car dealers will sell flood cars very cheap and they may even inform you that it is a flood car. Do not take a chance on any of these even if they seem to run very well and the dealer assures you they are a great value. The dealer might have honestly checked the vehicle out thoroughly, but there is no way they can see every potential problem, even if they try.

If you find out that your vehicle has been in a flood, be prepared for the worst. This does not mean that the engine is going to blow up and leave stranded on the side of the road, but don’t be surprised if it does. When you get rid of the vehicle do not expect top dollar if you sell it, and you need to disclose the vehicle history to your potential buyers. Just like you they must be made aware, because when they buy that flooded car, they need to know what they are getting into.