EVAP System Leak Repair Cost

EVAP System Leak Repair Cost: Big Problem Or Nothing To Worry?

Imagine driving down the highway, and then suddenly your check engine lights flash. Then a Diagnostic Trouble Code P0442, P0455, or P0456 is shown on scanning your DTC Computer. Gosh! One thing is for sure, there is a leak in your Evaporative Emission System (EVAP) and you have no choice but have to deal with the EVAP system leak repair cost.

It just doesn’t seem fair that this system, this thing that your car doesn’t even need to run, should cause so much aggravation.

The EVAP system is a closed system in your vehicle. It captures vapors from the fuel tank and keeps them from leaking out into the atmosphere. This makes the vehicle more environmentally friendly to operate.

If the check engine light comes on because of a problem or specific failure within that system, it’s very unlikely you’ll notice any difference in the actual operation of the vehicle. That’s because the EVAP system doesn’t affect your driving, it only affects your emissions.

There are a variety of potential causes for EVAP system issues, including leaks, a missing or loose fuel cap, an incorrect type of fuel cap used on the vehicle or leaks in the fuel tank, evaporative emission canister, evaporative emission system hose, purge valve or vent valve.

In this article, we discuss:

EVAP System

The Evaporative Emission Control (EVAP) System seals the fuel system of the vehicle to prevent fuel vapors (gasoline) from the fuel tank and fuel system from escaping into the atmosphere.

This is important because fuel vapors contain a variety of hydrocarbons. Hydrocarbons form smog when they react with air and sunlight.

EVAP System Repair Cost

Gasoline evaporates quickly, so if the fuel system is open to the atmosphere, a vehicle can pollute 24 hours per day without even being turned on. These uncontrolled evaporative emissions account for as much as 20% of the pollution produced by a vehicle.

The EVAP system usually requires no maintenance, but faults can turn on the check engine light and prevent a vehicle from passing an OBD II plug-in emissions test.


The OBD II EVAP monitor on 1996 and newer vehicles runs diagnostic self-checks to detect fuel vapor leaks, and if it finds any (including a loose or missing gas cap), it will set a fault code and turn on the check engine light. However, the EVAP monitor only runs under certain operating conditions. This may create a problem for the vehicle owner if his vehicle must be given an OBD II plug-in emissions test, and the monitor has not completed.

Common problems with the EVAP system include faults with the purge valve that vents fuel vapors to the engine, leaks in the vent and vacuum hoses, and loose, ill-fitting, or missing gas caps. The most common fault code is P0440, which shows a large leak (often a loose gas cap). EVAP Purge valve codes P0443 to P0449 are also common.

The code you don’t want to see is a P0442. This shows the system has detected a SMALL leak, but small leaks can often be a BIG problem to find. By small, we mean a leak no larger than a pinprick! Such small leaks are virtually impossible to find visually, so a special tester called a smoke machine is usually necessary to reveal the leak.

The smoke machine feeds a mineral-oil-based vapor into the EVAP system under light pressure (only a few pounds per square inch). The smoke may also contain an ultraviolet dye to make it easier to see under UV light.

Fixing EVAP codes can be a challenge, even for professional technicians. And if you have a P0442 small leak code, you will probably have to take your car to a repair shop that has a smoke machine and deal with EVAP system leak repair costs.

What Is EVAP System

The Evaporative Emission Control System EVAP system comprises the following components:

#1. Fuel Tank

The fuel tank stores the gasoline when you fill it up. But, you know when people tell you not to continue filling the tank after the pump automatically stops? That is because the tank has some expansion space at the top so the fuel can expand without overflowing or forcing the EVAP system to leak.

#2. Gas Cap

Tighten until it clicks. The gas cap seals off the filler neck of the gas tank from the outside atmosphere. Damaged or missing gas caps are the most common cause of EVAP system leak codes that trigger the check engine light.

#3. Liquid-Vapor Separator

This prevents liquid gasoline from entering the EVAP canister, which would overload its ability to store fuel vapors.

#4. EVAP Canister

This canister is connected to the fuel tank by the tank vent line. The EVAP canister houses 1 to 2 pounds of activated charcoal that acts like a sponge by absorbing and storing fuel vapors until the purge valve opens and allows the vacuum of the engine intake to siphon the fuel vapors from the charcoal into the engine intake manifold.

#5. Vent Control Valve

This allows the flow of the fuel vapors from the fuel tank into the EVAP canister.

#6. Purge Valve/Sensor

Allows engine intake vacuum to siphon the precise amount of fuel vapors from the EVAP canister into the engine intake manifold.

#7. Vent Hoses

The means by which the fuel vapors flow to different components of the EVAP system.

#8. Fuel Tank Pressure Sensor

Monitors the pressure within the fuel tank for leaks and to make sure too much pressure does not build.

#9. Fuel Level Sensor

Monitors the level of fuel in the tank.

Which Are The Available EVAP Systems

There are different evaporative emissions control systems. These systems can be classified into five different categories:

  • Diurnal: This usually represents gasoline that evaporates because of the rise in ambient temperature.
  • Running losses: Represent gasoline that vaporizes because of the heat of the engine and exhaust system during normal operation.
  • Resting losses: Natural permeation that occurs from the fuel delivery system while not operating under ambient conditions.
  • Hot Soak: Vaporization of fuel because of the kept heat of the engine after the engine is turned off.
  • Refueling: Represents the fuel vapors that escape from the tank by the displacement of liquid fuel.

Why Is An EVAP System Necessary In A Car

The EPA requires EVAP systems on cars because gasoline fuel vapors contain a variety of different hydrocarbons (HC). The lighter elements in gasoline evaporate easily, especially in warm weather. These include aldehydes, aromatics, olefins, and higher paraffins. These substances react with air and sunlight (called a photochemical reaction) to form smog.

Aldehydes are often called instant smog because they can form smog without undergoing photochemical changes.

The bad thing about fuel vapors is that fuel evaporates any time there is fuel in the tank. That means if the fuel system is unsealed or open to the atmosphere, it can pollute 24 hours a day even if the vehicle is not being driven.

Uncontrolled evaporative emissions like this can account for as much as 20 percent of the pollution produced by a motor vehicle.

The EVAP system eliminates fuel vapors as a source of air pollution by sealing off the fuel system from the atmosphere. Vent lines from the fuel tank and carburetor bowl route vapors to the EVAP storage canister, where they are trapped and stored until the engine is started.

When the engine is warm and the vehicle is going down the road, the PCM then opens a purge valve, allowing the vapors to be siphoned from the storage canister into the intake manifold. The fuel vapors are then burned in the engine.

Evaporative emission controls were first required on cars sold in California in 1970. EVAP has been used on all cars and light trucks since the early 1970s.

How Does EVAP System Work

The evaporative emission control (EVAP) system captures gasoline fumes and other emissions. When the fuel evaporates inside the gas tank, the excess vapors are transferred to the charcoal canister. They’re stored there until they can safely be transferred back to the engine to be burned with the normal air-fuel mixture.

When that’s ready to happen, a valve creates a vacuum that draws the vapors into the engine. Fresh air is also drawn in through the vents and valves to mix with the vapors for better combustion. These systems can be controlled mechanically, or like on newer cars, through the engine’s computer.

If the fuel tank was sealed tight, the fuel pump could create enough negative pressure to collapse it.

So, on older EVAP systems, the tank is vented by a spring-loaded valve inside the gas cap. While, On newer vehicles, it is vented through the EVAP canister.

It’s difficult to wrap your head around how a typical EVAP system works. But the good news is that the system’s functions can be broken down into three primary operations: storing fuel vapors, purging fuel vapors, and self-monitoring.

The EVAP system has three primary operations:

  • Storing fuel vapors.
  • Purging fuel vapors.
  • Self-monitoring.

#1. Storing Fuel Vapors

The vapor canister is the focal point of the EVAP system. When the engine is off, fuel vapors from the gas tank are stored in the canister. The canister contains activated charcoal, which traps the vapors until the engine is running, and conditions are correct for a vapor purge.

Normally, the vapor canister is open to the atmosphere to allow fresh air to enter. The canister is only closed when the EVAP monitor is run.

#2. Purging Fuel Vapors

In modern vehicles, the PCM determines when to start a canister purge. When the module deems conditions to be correct, it commands a solenoid to open the purge valve.

Opening the purge valve creates a vacuum that pulls fresh air through the vapor canister. The fresh air picks up the fuel vapors and delivers them to the engine to be burned during the normal combustion process.

#3. Monitoring For Leaks And Proper System Operation

As was mentioned, all vehicles built after 1999 have enhanced EVAP systems that can perform self-tests for both leaks and proper system operation. This test sequence is referred to as the EVAP monitor.

The monitoring strategy will vary, depending on the type of vehicle. When the conditions are correct, the control module closes the vent valve and opens the purge valve, creating a vacuum in the system.

The control module then monitors the fuel tank pressure (FTP) sensor to verify the system can reach a specified amount of vacuum.

If the vacuum is lower than specified, the module assumes there is a large leak somewhere in the system and stores a DTC in its memory.


An EVAP system leak is a leak somewhere in the EVAP system. If the size of the leak exceeds a certain value, the PCM will notice it while running the EVAP monitor. When this happens, the module turns on the check engine light and stores a DTC in its memory.

A professional technician (or skilled DIYer) can retrieve these codes with a scan tool or code reader.

Sometimes, an EVAP system leak may also trigger the check gas cap warning (on vehicles so equipped). When this happens, you have an EVAP system repair cost awaiting you to keep your car environmentally friendly.

The EVAP monitor tests the system for both small and large leaks. Examples of DTCs that correspond to leaks include:

  • P0442 Evaporative Emission System Leak Detected (small leak)
  • P0455 Evaporative Emission System Leak Detected (gross leak/no flow)
  • P0456 Evaporative Emission System Leak Detected (tiny leak)

A loose gas cap causes an EVAP system leak code. If your car has a leak code stored, try tightening the gas cap. If that doesn’t do the trick, you might swap out the gas cap, since replacements are relatively inexpensive.

Pinpointing an EVAP leak that’s not the gas cap can be difficult. Usually, the process requires the use of a professional smoke machine, which forces smoke into the EVAP system so that (hopefully) the leak will become visible when smoke billows out.

EVAP Leak Symptoms

Potential signs of an EVAP system leak can unfold in different ways. And when you see any of these signs, then prepare for an EVAP system leak repair cost to fix the leak immediately. These symptoms include;

EVAP System Leak Repair Cost, Symptoms #1. Poor Gas Mileage

A low gas mileage shows that your vehicle is not operating at optimum efficiency. It also signifies that there is a high consumption or leakage of gas in your vehicle’s system. Several factors can make your vehicle have low gas mileage, including a lousy EVAP system. Here, this happens because the fuel vapors your vehicle usually uses during combustion get burned up to the environment before getting to the combustion chamber.

This means that you will lose some amount of your gas usually used during combustion, which causes your vehicle to have low gas mileage, increasing your budget by buying gas for the vehicle. This can get your vapor canister saturated or clogged.

EVAP System Leak Repair Cost, Symptoms #2. Poor Engine Performance

An EVAP system leak is bound to cause poor engine performance. Your engine will have a less effective operation, producing not enough power for any acceleration. This might cause your vehicle to have a sluggish movement, even as you apply pressure on your gas pedal.

An incomplete combustion process generated because of an EVAP system leak will cause your vehicle to have a sluggish acceleration, which you have to address immediately to prevent any undesirable conditions.

EVAP System Leak Repair Cost, Symptoms #3. Difficulty In Starting Up The Engine

Difficult starting is also among the symptoms showing your vehicle has an EVAP system leak. This is because of a vacuum leak developed from issues with your charcoal canister, and it might make your vehicle’s engine difficult to kick off.

When you have a vacuum leak, it will permit unmetered air into your engine, which can unbalance the mixture of the air-fuel ratio, which will develop issues in your engine’s system by disturbing the internal combustion process. If this fault is left to continue, it can eventually lead to your vehicle not starting.

An unbalanced air-fuel ratio during combustion can lead to improper combustion because of an exorbitant amount of air in the engine.

EVAP System Leak Repair Cost, Symptoms #4. Engine Check Light Turns ON

Your engine check light will come ON when you have an EVAP system leak. If your vehicle’s computer system detects a fault within your EVAP system, it will illuminate the engine check light to tell the driver that there is an issue with the engine system.

The computer system picks up this fault via signals from your EVAP system. However, the engine check light can turn ON because of several other problems, so it’s advisable to properly scan your vehicle for error codes with an OTC Leak Tamer or use another smoke machine to get the actual fault responsible for turning the engine check light ON.

EVAP System Leak Repair Cost, Symptoms #5. Rough Idling

A prevalent symptom of an EVAP system leak is when your vehicle has a rough idle. The vehicle cannot maintain a high speed because of an unstable rpm count, or you might feel a shaking sensation in your vehicle while driving. Usually, your vehicle should have a stable rpm rate of about 1000.

If this rpm is fluctuating, you are looking at an idling issue. Rough idling can be because of faulty spark plugs, carburetor problems, dirty fuel injectors, and a vacuum leak.

A vacuum leak can occur because of a damaged or faulty EVAP system or hoses. When you notice this symptom, you need to immediately attend to it, as it can severely damage your engine system.

EVAP System Leak Repair Cost, Symptoms #6. Gasoline Odor

Gasoline odor is among an EVAP system leak symptoms and can result from various faults or engine problems in your vehicle’s system, but one of the major causes is a broken EVAP canister. A damaged vapor canister can give out a strong gasoline smell when it is bad.

EVAP System Leak Repair Cost, Symptoms #7. Failed Emission Test

Your vehicle will fail emission testing if you have an EVAP system leak in your system because of the emission of gas fumes. This type of fault will also illuminate the engine check light.

EVAP System Leak Repair Cost, Symptoms #8. Hissing Sound

A hissing sound coming from the engine is a common sign of a vacuum leak, which may be caused by a damaged EVAP system. The EVAP system is designed to capture fuel vapors and prevent them from escaping into the atmosphere. When there is a leak in the system, it can cause a hissing sound as the air and fuel vapors escape. This sound is usually more noticeable when the engine is idling. If you hear a hissing sound coming from your engine, it is essential to get it checked out as soon as possible to prevent further damage to your vehicle.

EVAP System Leak Repair Cost, Symptoms #9. Difficulty Filling Gas Tank

Another symptom of an EVAP system leak is having trouble filling your gas tank. The EVAP system is designed to allow air to escape from the gas tank while filling it with fuel. If the system is damaged or clogged, it can prevent air from escaping, making it difficult to fill the tank. If you notice that the gas pump keeps shutting off while you are trying to fill your tank, it could be a sign of an EVAP system problem.

EVAP System Leak Repair Cost, Symptoms #10. Decreased Fuel Efficiency

Decreased fuel efficiency is another common symptom of an EVAP system leak. The EVAP system helps to capture fuel vapors and use them in the combustion process. When there is a leak in the system, it can cause fuel vapors to escape, leading to a decrease in fuel efficiency. If you notice that your vehicle is using more fuel than usual, it may be due to an EVAP system leak.

EVAP System Leak Repair Cost, Symptoms #11. Stalling

Stalling is another symptom that can occur due to an EVAP system leak. A vacuum leak can cause an imbalance in the air-fuel mixture, leading to stalling. If your vehicle stalls frequently, especially at idle or low speeds, it may be due to a vacuum leak in the EVAP system.

EVAP System Leak Repair Cost, Symptoms #12. Trouble Codes

When the vehicle’s computer detects a problem with the EVAP system, it will store a trouble code in the vehicle’s computer. These codes can be read with a scan tool to help diagnose the problem. Common trouble codes related to the EVAP system include P0440, PO441 code, P0442, P0446, and P0455. If your vehicle has any of these codes, it is essential to address the issue as soon as possible.

EVAP System Leak Repair Cost, Symptoms #13. Presence of Fuel in Charcoal Canister

The charcoal canister is a crucial component of the EVAP system. It is designed to absorb fuel vapors before they can escape into the atmosphere. Over time, the canister can become saturated with fuel, especially if there is a leak in the system. If you notice the presence of fuel in the charcoal canister, it is a sign that there may be a leak in the EVAP system.

EVAP System Leak Repair Cost, Symptoms #14. Damaged or Loose Gas Cap

The gas cap is an essential component of the EVAP system. It helps to seal the fuel tank and prevent fuel vapors from escaping. A damaged or loose gas cap can cause a leak in the EVAP system, leading to several of the symptoms mentioned above. If you notice that your gas cap is damaged, loose, or missing, it is essential to replace it as soon as possible.

EVAP System Leak Repair Cost, Symptoms #15. Vehicle Fails to Start

In extreme cases, an EVAP system leak can cause the vehicle to fail to start. This is because a significant vacuum leak can cause an imbalance in the air-fuel mixture, leading to improper combustion. If your vehicle fails to start and you have noticed any of the other symptoms mentioned above, it may be due to an EVAP system leak.

In conclusion, an EVAP system leak can cause various symptoms, from poor gas mileage to engine stalling. It is essential to address any of these issues as soon as possible to prevent further damage to your vehicle and the environment. If you notice any of these symptoms, it is recommended to have your vehicle inspected by a professional to determine the cause of the problem and fix it accordingly.

Evaporative Emission System Leak Detected

Finding leaks in the EVAP system can be very difficult. It often requires using a special “smoke machine” that generates a fine mineral oil mist that is pumped into the EVAP system under very light pressure. The mist circulates through the plumbing and eventually seeps out through the leak, making the leak visible. The mist may also contain ultraviolet dye to make any leaks more visible when illuminated with a UV lamp.

Below is a step-by-step fix to an EVAP System Leak Repair cost:

EVAP System Leak Repair Cost, Fixes Step #1

Verify that the gas cap is firmly tightened onto the gas tank entry point. The EVAP system also monitors the gas tank, so an open gas cap can be the primary source and perhaps the only leak in the system. Leave the fuel filler door open after you tighten the cap.

EVAP System Leak Repair Cost, Fixes Step #2

Kick a pair of chocks behind the rear wheels and lift the front end of the vehicle with a floor jack far enough that you can fit underneath. Secure it on a pair of jack stands.

EVAP System Leak Repair Cost, Fixes Step #3

Locate the EVAP service port adapter within the engine’s compartment. Typically, the port is near the engine’s front on the passenger side. You’ll see a valve and supply hose protruding outward.

EVAP System Leak Repair Cost, Fixes Step #4

Place the smoke machine tester’s hose into the service port adapter. Turn on the smoke machine by choosing the “Test” mode.

EVAP System Leak Repair Cost, Fixes Step #5

Allow the smoke to fill the EVAP system for approximately 60 seconds and dim the lights in your work area. Complete darkness would be preferred, if not for the obvious danger of hitting your face in a car.

EVAP System Leak Repair Cost, Fixes Step #6

Visually inspect the EVAP system by running the UV light across the vehicle’s underside, following the system’s path from the engine compartment to the rear fuel tank. Any smoke leaking from the system will illuminate in ultraviolet light.

Check the fuel cap; cap seal failures are very common in older vehicles. Replace any leaking or cracked hose within the EVAP system. In addition, repair or replace any EVAP purge valve that may emit fumes.

Can You Drive Despite An EVAP System Leak

The answer is, yes, it’s usually safe to continue driving. But because the leak increases the amount of pollution the vehicle emits, fix the problem as soon as possible.

EVAP systems can also suffer from problems other than leaks. There’s a wide range of DTCs devoted to everything from a blocked vent valve to inadequate purge flow.

What Is EVAP System Leak Repair Cost

EVAP system repair costs can be between $100 to $600. The cost of repair depends on two factors: the leakage location and the cause of leakage. However, other causes require a minor repair to fix, which will not cost so much.

But if the repair requires the replacement of various components in your EVAP system, it can build up to a high repair cost. Your vehicle’s model is also a determining factor of how high your repair cost will amount to.

The EVAP (Evaporative Emission Control) system is crucial in preventing the release of harmful fuel vapors into the atmosphere. However, leaks in this system can occur due to various reasons, and repairing them is essential to maintain your car’s efficiency and to protect the environment.

1. Components of the EVAP System and Repair Costs

Let’s delve into the various components that might need repair or replacement in case of an EVAP system leak, their associated costs, and what you need to look out for…

  1. Fuel Cap: A loose or damaged fuel cap is the most common cause of an EVAP system leak. Ensure it is tightly secured. If the cap is damaged, it needs to be replaced. Cost: Replacement usually ranges from $20-$60.
  2. EVAP Line: These are hoses that connect different parts of the EVAP system. Cracks or holes in these lines can cause leaks. Cost: Replacement of the EVAP line typically costs between $50-$100.
  3. EVAP Purge Valve: This valve controls the flow of vapors from the charcoal canister to the engine. A malfunctioning purge valve can lead to leaks. Cost: Replacement generally ranges from $150-$200.
  4. Charcoal Canister: The charcoal canister stores fuel vapors before they are sent to the engine to be burned. Over time, the canister can get damaged or clogged. Cost: Replacing a charcoal canister can cost between $200-$600.
  5. Charcoal Canister Vent Control Valve: This valve controls the air that flows into the charcoal canister. A faulty vent control valve can lead to a buildup of pressure, causing leaks. Cost: Replacement usually ranges from $150-$200.
  6. Gas Tank: The gas tank can develop cracks or holes, leading to fuel vapor leaks. This is a rare but serious issue. Cost: Repairing or replacing a gas tank can cost anywhere from $200-$1000, depending on the severity of the damage.

2. Factors to Consider

  1. Severity of the Leak: Minor leaks can often be resolved by tightening or replacing the gas cap. However, more severe leaks may require the replacement of multiple components, escalating the costs.
  2. Labor Costs: The above estimates are for parts only. Labor costs can vary depending on the location and complexity of the repair. Usually, labor charges range from $75-$150.
  3. Vehicle Make and Model: The cost of replacement parts and labor can vary significantly based on the vehicle’s make and model.

Preventing and repairing EVAP system leaks is essential for your vehicle’s performance and for protecting the environment. Regularly inspect the gas cap and other components of the EVAP system for signs of wear or damage.

If you notice any issues, it’s essential to address them promptly to avoid further damage and costlier repairs. Keep in mind that the cost of repairs can vary based on several factors, including the severity of the leak, labor costs, and your vehicle’s make and model.

Reliability: EVAP System Leak Repair Cost

The biggest benefit of getting the EVAP system repaired or replaced is that you will experience better gas mileage. Saving money on fuel and going further on a single tank is an advantage. You’ll also produce emissions at a reduced rate. You can pass an emissions test if one is required, but only after you have had the new EVAP system put in.

Fuel Evaporative Canister Replacement Facts:

  1. The average cost for a fuel evaporative canister replacement ranges from $430 to $483, with labor costs estimated between $92 and $116 while parts are priced between $338 and $367.
  2. The location and type of vehicle can affect the cost of fuel evaporative canister replacement.
  3. Repair services for fuel evaporative canister replacement are the least expensive in Milwaukee, WI, while they can be most expensive in Phoenix, AZ.
  4. The fuel evaporative canister, also known as the charcoal canister, is an emission control device that traps fuel vapor and sends it to the fuel tank for later use.
  5. The EVAP system uses the charcoal canister to store fuel vapor that escapes the gas tank through a tube, and the charcoal canister empties by engine vacuum sucking the vapors out to be burned as fuel.
  6. The vent valve and purge valve must be opened simultaneously for the evaporative canister to empty, and closed to store vapors until the vents are opened to prevent fuel vapors from entering the atmosphere and increase fuel mileage.
  7. A failed EVAP system test will cause the check engine light to illuminate and store trouble codes in the vehicle’s memory.
  8. Symptoms of a bad fuel evaporative canister include difficulty starting the engine, rough idle, poor fuel mileage, and in some models, a popping sound.
  9. A vehicle with an EVAP system issue can still be driven, but may achieve lower fuel mileage and will not pass state or federal emission testing.
  10. Regular cleaning and inspection of the fuel cap can prevent EVAP system failures and related trouble codes.

Final Thought: EVAP System Leak Repair Cost

First, the (EVAP) emission control system; prevents the escape of fuel vapors from a vehicle’s fuel system. So, when the engine is running, a purge valve opens, allowing the vacuum to siphon the fuel vapors into the engine.

In addition, fixing (EVAP) codes can be a challenge, even for professional technicians. In addition, if you have a P0442 small leak code, you’ll probably have to use a smoke machine to find it and this might increase your EVAP system leak repair cost.

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