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EVAP Leaks: Why Do They Happen And How Do I Fix Them?

What Is An EVAP Leak? What Is The EVAP System?

EVAP leak is an auto part fault in your vehicle’s evaporative emission control system

EVAP system prevents gasoline vapors from escaping into the atmosphere
Credit: aa1car.com


Simply put, an EVAP leak is an auto part fault in your vehicle’s evaporative emission control system (or EVAP for short). Because of the nature of the EVAP system, this means that gasoline fumes are leaking from your gas tank, even when it is not in operation. As such, an EVAP leak could potentially pose a threat to your well-being as well as the health and safety of those around you.

When operating regularly, the EVAP system works to contain extra gas fumes from your gas tank and prevent them from leaching out into the air and atmosphere. This, in turn, cuts down on the overall air pollution, a hazardous problem that has become particularly acute in urban environments over the past several decades. The EVAP system is just one of several vehicle components designed to combat unchecked pollution.

EVAP System

The EVAP system is made up of several parts, all of which can face some type of trouble over the lifespan of your vehicle. This includes the gas tank, gas cap, liquid-vapor separator, and EVAP canister.

How Do You Find And Identify An EVAP Leak?

 If your Check Engine Light does come on, and you just filled up your gas tank, check the gas cap to see if it's loose
Check Engine Light
can indicate any number of vehicular problems, including problems with the EVAP system
Credit: commons.wikimedia.org

There are several methods for identifying an EVAP leak, including several systems built into your vehicle. One of these methods is by noticing that the “Check Engine” light has become illuminated while operating the vehicle. This light (also knowns as the “malfunction indicator light” or MIL for short) can indicate any number of vehicular problems, including problems with the EVAP system. If you take your vehicle to a mechanic to read out the specific fault code, they may determine that the light was caused by problems with the EVAP system.

Another sure sign that something is amiss with the EVAP system is a persistent and lingering smell of gasoline in and around your vehicle. While this may be a residual smell after a tank fills up, it may also indicate that some gaseous fumes are escaping the main tank. One place that this smell may be most apparent is wherever the car spends the most time when inactive, such as a garage.

Loose Gas Cap is the most common cause of an EVAP leak.
Credit: commons.wikimedia.org

Also, if you notice an active leak from your gas tank (in the garage or elsewhere), this is also likely a sign that the EVAP system is having some trouble. If this later scenario is the case, do not operate your vehicle until a trained professional has an opportunity to evaluate it.

How Do You Fix An EVAP Leak? How Do I Complete a Manual or Scan Test?

Though fixing an EVAP leak can take some time and knowledge, there are some simple fixes that you can try before seeking out a mechanic.

First and foremost, manually check to ensure that your gas cap is both secured correctly and remains secured after driving the vehicle. In some cases, the O ring inside the cap may degrade, causing it to deteriorate and leave an opening in the vacuum-sealed EVAP system. This is the most common type of EVAP leak and the simplest to fix.

Using an OBD-II scanner (available at most auto parts stores), you can also check the EVAP status based on internal computer readouts. After following the instructions to perform a scan, your scanner will return an error code (if a fault is present). If the code ranges from P0440 to P0457, you may have an EVAP leak on your hands (see below for more information).

Beyond this though, you will likely need to seek out a mechanic in order to resolve your EVAP problem. Other potential problems could involve a faulty vacuum control solenoid as well as faulty purge solenoid. In either case, specialist knowledge and tools will be needed to access the majority of the EVAP system, located under the vehicle and near to the gas tank.

What Is An EVAP Error Code?

An EVAP error code is a specialized output by your vehicle’s on-board diagnostics system (OBD-II) to indicate something is amiss with your EVAP system. If such an error code ranges from P0440 to P0457, then you are likely going to need to seek out professional help to resolve the leak and the code.

Is It Safe To Drive With an EVAP Leak?

You should not drive for long while when having a leak.

EVAP leaks do not immediately affect how your vehicle operates.
Credit: pixabay.com

In general, EVAP leaks do not immediately affect how your vehicle operates. However, that does not mean you should disregard it out of hand. In fact, because this leak involves a portion of the gas tank system, you should take it rather seriously.

Anytime leaking liquid gas or gas fumes are involved, you and those around you are at risk to inhalation or injury from ignition. Though these are not likely, they are still a potential risk that comes with operating with a persistent and unresolved. EVAP leak.

In any case, driving with an EVAP leaks means that you are very likely polluting the air on 24/7 basis. While this is bad for the environment at large, it also means that you are likely to fail a state-mandated emissions test, should one be administered.

The Bottom Line

The short and long of EVAP system leaks is that you should take them seriously. With a potential leak in petroleum fumes, you may be harming not only yourself but also the people and environment around you.

While you may be able to quickly identify an EVAP leak based on the smell of gaseous fumes, you may need to seek out a mechanic to fully resolve it (beyond attempting several manual and scan-based tests). While it is regularly safe to drive with an EVAP leak, you should only attempt to do so for as long as it takes to bring the vehicle to a mechanic for repairs.Now that you know about EVAP leaks and how to resolve them, you can make informed decisions regarding your vehicle’s future maintenance.

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