An evaporative emission system leak can set off your vehicle’s check engine light. However, an illuminating check engine light can be caused by a number of reasons. But if you notice that your check engine light is on and you find trouble codes such as P0455 or P0456, it means that there is a leak somewhere in your evaporative emission system. It might be caused by a problem that is as simple as a loose or faulty gas cap or something serious like a damaged EVAP system component. An evaporative emission system leak might not be that damaging to the engine or to the vehicle, but it is something that you should not take lightly since a leaking EVAP system means that harmful vapors are being emitted in the atmosphere.
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Evaporative Emission System Leak: How Serious is an Evaporative Emission System Leak?
To understand whether an evaporative emission system leak is something that we should worry about or not, we need to understand what is an evaporative emission or EVAP system and what it does.
The evaporative emission control system equipped in the vehicle is necessary so the drivers can comply with the current regulations governing evaporative emissions. This is because the oil and fuel used in a vehicle emits vapors that are very toxic to the environment. The EVAP system is the one that keeps these gas vapor in the fuel tank and directs them to the engine to be burned.
The EVAP system has a number of components that include the fuel tank, gas cap, liquid-vapor separator, and the EVAP canister. It also has a complex web of hoses, filters, valves, and many others. All these components work together to ensure that the fuel vapors won’t escape from the fuel tank or fuel system and get into the atmosphere.
Although the evaporative emission system does not really need any maintenance, it can trigger some faults that can set off the check engine light. When this happens, a car might not be able to pass an OBD2 plug-in emissions test.
There is an EVAP system monitor that enables the car’s onboard computer to test the integrity of the fuel system as well as its capacity to draw gas vapors into the engine for combustion. During the canister purge operation that happens when the engine is operating, a part of the monitor is activated and there may also be a leak detection portion of the monitor activated under normal engine operating conditions like when in extended idle or after the car has been shut off.
This evaporative emission system monitor inspects for gas vapor leaks by doing either a vacuum or pressure test on the car’s fuel system. The federal standard lets leaks up to the equivalent of a hole 0.40 inches in diameter in a gas vapor or filler cap for cars in model years 1996 to 1999 and 0.20 inch-diameter hole for the 2000 and newer cars.
The EVAP monitor running requirements can vary depending on the car’s make, model, and year. Tests will be done and all of the components in the evaporative emission system should be functioning properly in order to pass. However, if there are any trouble codes that are EVAP related, it will keep the EVAP system monitor from running. This can be a problem for you.
Problems that usually occur with the EVAP system include trouble codes with the vapor canister purge valve, vent and vacuum hoses leaks, and loose or faulty fuel caps. The trouble code P0440 is the most common fault code, it is the general code for a problem with the fuel evaporative emission system. It is associated with the codes P0442, P0455 and P0456 which are the codes for the evaporative emission system leak.
Among all the problems that can happen to your evaporative emission system, you don’t want to deal with an evaporative emission system leak. Because a leak, no matter how small or big it is, is a serious problem. Small leaks can be hard to find since they can be no larger than a pinhole. There are instances where a smoke machine will be needed to find the leak.
If you are asking how serious is an evaporative emission system leak, consider these reasons:
- An evaporative emission system leak can cause you to fail some emission tests or the EVAP system monitor.
- A vehicle with an evaporative emission system leak is very harmful to the environment.
You need to remember that the EVAP system on the vehicle is very important since they keep the harmful gas vapors from being released to the atmosphere. These fuel vapors have a number of hydrocarbons. When the weather is warmer, the lighter elements of the fuel such as the aldehydes, olefins, aromatics, and higher paraffins tend to evaporate easily. Substances such as these ones react with sunlight and air to become a smog. In fact, the aldehydes are known to be an instant smog since they can become a smog even without going through any photochemical changes.
The EVAP system is very vital because these gas vapors can evaporate whenever there is gas in the fuel tank. If the car is filled with fuel everyday, it means that it can pollute the air everyday too, 24 hours a day, if the fuel system is unsealed or open, contributing twenty percent of the pollution made by motor vehicles. An EVAP system that is working efficiently can prevent these gas vapors from being a source of air pollution by sealing off the fuel system. That is why it is important that you don’t ignore an evaporative emission system leak.
Evaporative Emission System Leak: What Happens If You Don't Fix an EVAP Leak?
If your car has an evaporative emission system leak, it means that there are extra vapors emitting from your car. The gas vapors are being emitted at a higher level than usual and it is a problem since the EVAP system is supposed to keep these gas vapors from being released.
An evaporative emission system leak usually translates to an extra fuel consumption, extra pollution, and your engine wearing down at a much faster rate. The EVAP system is constantly monitored by the car’s onboard computer so the driver will be alerted immediately if it detects that gas vapors are being emitted in a damaging way.
The most common reason for an evaporative emission system leak is a faulty or loose gas cap. Even if the gas cap is just slightly loose, it can still allow gas vapors to enter the system. If you have just filled your gas tank and you noticed an illuminating check engine light, you need to check your gas cap and make sure that it is fitted and tightened properly.
An evaporative emission system leak caused by a loose gas cap can be fixed by tightening it and clearing the trouble codes. But if it does not work, it means that there is a more serious problem somewhere in the evaporative emission system. The problem might be caused by a punctured vapor hose or vapor tube, damaged fuel tank, faulty purge valve, a broken or worn out O-ring seal, and other system leaks that are affecting the car’s emissions. A poorly maintained car can also cause an evaporative emission system leak.
You will know if your car has an evaporative emission system leak if you experience any of the following symptoms:
- Illuminating check engine light.
Like mentioned earlier, a problem with the evaporative emission system can set off the check engine light. If you notice that your check engine light is on when you recently just filled up your gas tank, check your fuel cap and make sure that it is not loose.
- A slight drop of the car’s fuel mileage.
You may experience a slight drop of your car’s fuel mileage if you have an evaporative emission system leak. This is because the gas vapors that are stored in the charcoal canister will be released into the atmosphere instead of being burned and used in the combustion process. This causes your car to use some of the fuel to make up for the gas vapors that are usually used for combustion.
- Diagnostic trouble code or DTC in the system memory of the car.
If your car’s onboard computer detects that there is a leak in the EVAP system, it will set a trouble code. The DTC includes:
- P0440: Evaporative Emission Control System
- P0441: Evaporative Emission Control System Incorrect Purge Flow
- P0442: Evaporative Emission Control System Leak Detected (small leak)
- P0455: Evaporative Emission Control System Leak Detected (gross or large leak)
- P0456: Evaporative Emission Control System Leak Detected (very small leak)
- P0457: Evaporative Emission Control System Leak Detected (gas cap loose or off)
- P1440: Purge Valve Stuck Open
- P2421: Evaporative Emission Control System Vent Valve Stuck Open
- P2450: Evaporative Emission Control System Switching Valve Performance
Evaporative Emission System Leak: How Do You Fix an Evaporative Emissions Leak?
To fix an evaporative emission system leak, you need to determine what causes it. If the problem is caused by a loose cap, you need to tighten the cap. If the gas cap has already weakened or damaged, you will have to replace it with a new one. You just need to make sure that you get the right gas cap for your vehicle.
If the evaporative emission system leak is not caused by a loose cap, you can check the O-ring seals since they can weaken and suffer wear and tear as they age. Worn out O-rings can have gaps between the cap and the neck, causing a leak. The vacuum line should also be inspected since it is exposed to excessive engine heat and vibration that can result in cracks or tears.
If the problem is caused by something else, you will have to go under the hood and check the system’s other components. You can also read the stored trouble codes to determine what causes the problem and correct it.
However, as easy it may sound, finding an evaporative emission system leak can be very difficult. You may have to use some special equipment or tests to find the leak. One of the methods used to find an evaporative emission system leak is by doing a smoke test.
It can be done by blowing smoke into the EVAP system and looking for the smoke as it escapes from the damaged seal, valve, hose, or hose. Although this method can be very effective in finding leaks, it is not cheap. Smoke test machines can cost you between $150 and $800.
There are some do-it-yourself tutorial videos that can teach you how to perform smoke tests without using a smoke machine at home, but the risk is just too high. You will have to deal with flammable fumes and extreme pressures that can damage the EVAP system components. If you are not confident in doing it yourself, let the professionals handle it.
Other methods you can do to find a leak include a vacuum test that utilizes the engine vacuum gauge that is adapted to test the integrity of the valves and lines, using a hand vacuum pump to check the valves, and a bubble test that uses a soapy solution using windshield washer fluid and a car wash soap.
Repairing an evaporative emission system leak can be as easy as tightening a loose gas cap, but it can also be a complicated and expensive repair depending on what component is causing it or the location of the leak. Removing the damaged component and replacing it with a new one is usually the best solution.
Replacing valves can cost you between $25 and $100 for the parts, o-ring seals can be bought around $2, while replacing a worn gas cap can cost you around $15 to $75 on the parts alone.
Although a vehicle with an evaporative emission system leak can still be driven safely, it is best that you don’t drive it until the problem is repaired. Depending on the severity of the problem, the repair can be done yourself or by a professional. Just make sure that when you opt to do the repair yourself, always reset the diagnostic trouble codes.