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Learn How to Find & Fix an EVAP Leak

Learn How to Find & Fix an EVAP Leak

Out of all the ways in which your vehicle can fail, perhaps none are so frustrating as the “EVAP System Malfunction.” If not properly maintained, the EVAP system can bring your car to a stop. 


Imagine how quickly a small pool of gasoline disappears from a hot sidewalk, and you’ll get an idea of how much money is just drifting away through your leaking EVAP system. Yes, that is something you should seriously consider. 


Common EVAP Leak Locations


  1. Charcoal Canister


A puncture in the charcoal canister is a standard car issue. As the charcoal canister is usually located beneath the car, near the gas tank, rock and debris flying from the pavement sometimes hit the EVAP canister assembly and cracks it. 


For the same reason, hoses that connect to it might get separated or severed. This phenomenon is frequent in cars running in winter conditions.


  1. Seals and Hoses


Defective O-ring seals or damaged hoses are the most common cause of EVAP leaks. Rubber seals and hoses tend to dry up and crack and let the fumes to rise. Worse, there are tons of them in an EVAP assembly. The first thing to do to identify this kind of leak is to visually inspect every hose and line connections.


  1. Canister Vent Valve


A hole in the canister vent valve is another usual issue. The CVV takes care of driving the vapors in the charcoal canister, often closing and opening. Typically, older vent valves won’t close properly, and some of the fumes will get released into the environment. 


The canister vent valve is also placed right beside the charcoal canister to be pelted by rocks and debris and crack on many car models. In such a case, replacing the canister vent valve should solve the issue.


How to Find and Fix an EVAP Leak


Step 1

Ensure that the gas cap is clamped onto the gas tank entry point. The EVAP system also controls the gas tank so that an open gas cap can be the largest and the only leak in the system. Let the fuel filler door open after you tighten the lid.


Step 2

Kick a couple of chocks behind the rear wheels and elevate the vehicle’s front end using a floor jack at a suitable distance so that you can fit it underneath the car. Settle it on a pair of jack stands.


Step 3

Find the EVAP service port adapter inside the engine’s compartment. Usually, the port is close to the engine’s front on the passenger side. You’ll see a valve and supply hose pointing outward.


See Also

Step 4

Put the smoke machine tester’s hose inside the service port adapter. Switch on the smoke machine by choosing the “Test” mode.


Step 5

Let the smoke fill the EVAP system for about 60 seconds, and dim the lights in your work area. Total darkness is preferred, if not for the obvious danger of hitting your face in a car. 


Step 6

Visually examine the EVAP system by moving the UV light across the car’s underside, following the system’s path from the engine section to the rear fuel tank. Any smoke oozing from the system will lighten up in the ultraviolet light. Make sure to inspect the fuel cap as cap seal failures are widespread on older vehicles.


Replace any cracked or leaking hose within the EVAP system. Also, replace or repair any EVAP purge valve that may emit fumes. Car repairs can sometimes spiral out of budget, largely because of the high cost of spares. You can slash your repair expends significantly by purchasing cheap car parts from an online auto store.


Wrapping Up


Most EVAP system parts are built of plastic, seals & hoses and tend to crack with time. We hope that the tips and steps mentioned in this article will help you to find and fix an EVAP leak on your vehicle. Additionally, going through your car’s repair manual will always help. 


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