The intake manifold sucks air from its surroundings and funnels it to the engine’s valvetrain. This airflow through the pipes and tubing is crucial, as air is a vital ingredient for combustion and power production. In some vehicles, a turbocharger is used to push air into the engine, aiding power and efficiency. A leak somewhere along the engine’s intake system can cause less air to enter the engine, which can cause some problems.
When the vehicle develops intake-related symptoms such as stalling, lack of power, or poor efficiency, conducting a smoke test is a great way to diagnose whether your vehicle’s intake system has leaks.
Even though this method is used primarily for intake systems, smoke tests can also be used to find leaks in a vehicle’s evaporative emissions system or exhaust system.
What Is a Smoke Test on a Car?
A car smoke test is a procedure that’s done to your vehicle’s intake system to check for any leaks. This test involves using a smoke test machine to pump smoke into the engine’s intake or vacuum hoses. As the smoke travels through the system, the smoke will seep through any leaks. If there are leaks, then the smoke should come out of the pipes, couplers, or clamps. Most smoke tests keep smoke at a moderate level so that it doesn’t damage the engine. Once the leak has been identified, the leaking component can either be repaired or replaced.
Why Is a Smoke Test Necessary?
Most cars use plumbing to facilitate airflow to the engine. Over time, the joints between these plumbing can come loose or fail, creating leaks. Loose couplers, fittings, clamps, and hoses are the most common culprits.
Smoke tests are necessary if you want to find small and hidden leaks. Large leaks in the intake system can create whooshing noises, which can be found without requiring a smoke test. However, vacuum leak testing with smoke makes finding small leaks easy.
For the most part, a small leak is a minor issue and won’t cause major drivability issues. These small leaks can trigger an illuminated check engine light and a stored trouble code in your vehicle’s diagnostic system, as the mass air flow sensor can detect the extra or lackluster airflow. Small air leaks can cause your vehicle to have lackluster boost pressure or have a lean running engine.
These small leaks might not mean much, but they can make a difference if you intend to race your vehicle on the track and you want the most performance.
How To Conduct a Smoke Test
Conducting a smoke test involves using a smoke generator designed for automotive testing. There are high-tech diagnostic smoke machines where you can control the amount of smoke and air pressure. There are also makeshift smoke machines that use glass jars, hoses, soldering iron, rags, and baby oil. These smoke machines use a soldering iron to burn baby oil in the glass jar. There are a lot of online videos on how to make a homemade smoke machine.
In a smoke test, plastic tubing funnels the heated and smoky air into the engine’s intake manifold, evaporative emissions system, or even exhaust system.
An easy path for the smoke to enter the intake system is through the positive crankcase ventilation (PCV) vacuum hose, which hooks up to the intake manifold. Once the smoke generator is pumping smoke into the system, you should try to find where the smoke is leaking. Using a powerful light is going to help make any small leaks more visible. You should continue pumping air into the channels for about thirty minutes to ensure the smoke gets into all the nooks and crannies.
How Much Is a Car Smoke Test?
The cost of conducting a smoke test in an auto repair shop will be around $50 to $150. The cost might increase if you’re conducting a smoke test on several vehicle systems.
If the smoke test reveals a problem, then you likely need to spend more to resolve the issue. This might require purchasing new components and spending on labor.
If you conduct the smoke test yourself using a homemade smoke machine, then you’ll likely end up spending only a fraction of the cost.
When Do You Need To Conduct a Car Smoke Test?
When to do a smoke test on a car? A smoke test can be considered if your vehicle is showing these symptoms:
- A hissing sound from the engine bay when the vehicle is running
- A higher idle RPM
- An illuminated check engine light
- Increased fuel consumption
- Reduced power and ability to accelerate
A minor air leak in the intake manifold isn’t a major issue. However, if this small leak is allowed to persist, it can worsen. When this happens, the engine might have trouble idling and can stall.
As much as possible, you should seek a professional when diagnosing and fixing issues since they’ll be equipped with the right tools needed for a smoke test. Additionally, they’ll have the right skills to fix any issue they might find.
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