Smoke Test for Car – How to Test and Cost

What is a car smoke test? Car leaks pose a great risk to the operational efficiency of your car. To find the leak, a car smoke leak test is used. In this article, I will describe how car smoke leak tests are used to determine where these leaks are coming from.

What is a smoke leak test for a car? A smoke leak test provides information on possible leaks present under a car’s hood. The car’s vacuum systems will be tested using a smoke machine. The smoke will come out of any holes in the piping to indicate the leaks to be sealed.

How to do a smoke test on a car? To do a smoke test, you infuse smoke from a smoke machine into the car’s vacuum systems. If you see smoke escaping in one of the vacuum systems, a leak is likely present. Most car services use gray smoke, although some use other colors to make the smoke more visible.

What does a smoke test for a car cost? A smoke car leak test costs about $89.99. Professional smoke machines range from $150 to $800. There isn’t one test, but a series of tests done to determine if there are air and gas leaks under the hood of a vehicle.

Read on to learn more about a smoke leak test for cars and how it is performed.

smoke test car

Smoke Test – Car Leak Test Cost and How to Test

What is a smoke leak test on a car? A smoke test for cars is called a smoke leak test. It is done to examine the vacuum systems of a car for leaks thoroughly. Once this leak test is done, you will know if there is a leak in any piping of the car’s vacuum systems.

The vehicle’s vacuum system manages the flow of air in and out of the engine. If there’s any leak, it will compromise the performance of the engine. It will influence the car computer to supply more fuel to the engine when it is not really required. So the air to fuel ratio of the car is thrown off-balance.

Professionals do a car smoke test to find any leak in any of the car’s hollow parts, such as the intake manifold, evaporative emission system, and exhaust system. They conduct this test just like what you will do if you want to find a water bucket leak. Just fill the bucket with water and check the spots where the liquid drips out.

A similar thing is done in a vehicle smoke test. In a smoke test, you will fill up the hollow parts of the three systems mentioned above with smoke and check the spots where the smoke is coming out. The work will be easier if you use a bright lamp to see where the smoke is coming out. Scan the light along the hollow parts of the three systems to see if there’s smoke.

Technically speaking, mechanics do a smoke leak test to check the possible leaks under the hood of your car, specifically in the car’s vacuum systems. The vacuum systems include the three systems I mentioned above. This test will show you if there is any piping in these three systems that leaks.

If there are any leaks in any of these vacuum systems, it will adversely affect the car engine’s performance. The engine’s fuel to air ratio will be thrown off-balance if it receives an unmeasured airflow.

For instance, if your car’s engine seems to hesitate when starting, that could be one sign of an air leak. Or your car may have poor acceleration, or the power of its engine seems to have lowered. If you or a mechanic perform a smoke leak test on the car’s vacuum systems, then you’ll know the problem.

What does a smoke test for a car cost? A smoke car leak test costs about $89.99. The cost of a professional smoke machine ranges from $150 to $800. There isn’t one test, but several tests conducted to determine if there are any air and gas leaks under the hood of a vehicle.

Importance of a Smoke Leak Test for a Car

If you suspect a leak in your system, it is very important to have it smoke tested. Just a small leak, as tiny as 0.030 of an inch, will affect and lower engine performance. The first thing that will happen is the Check Engine light will turn on. Then the leaks will compromise the drivability of the car.

If you want to drive safely and risk no accident, you need to perform a smoke leak test on your car. It would help if you did this when you feel a leak in your car’s vacuum systems. Professional car mechanics understand the value of a smoke machine because it helps them pinpoint the issues.

The smoke machine also helps them prevent serious damage to the car because of the owner’s neglect. If there are any related issues in a car, the Check Engine light will turn on as soon as you start the car – and it will remain lighted. That indicates that the car engine has a problem.

And if your car has trouble accelerating, it indicates that there could be a leak somewhere. You may hear a whistling sound indicating that there’s something wrong. It really depends on how big the leak is. Upon performing a smoke leak test, you can clear all these uncertainties. If you perform this test, you will avoid more costly damage to your car.

car smoke test

How to Do a Smoke Test on a Car?

How to smoke test a car? You will need a smoke testing machine to execute a smoke leak test properly. Most car repair services and garages have this machine as a standard testing tool. Tracing vacuum leaks is not a job for the weekend mechanic.

If you are not a mechanic, you may perform some of the more rudimentary elementary tasks of the smoke leak test. But certainly not the kind of work that requires specialized skills, know-how, and experience of a professional car mechanic.  

Today’s cars have engine vacuums that control a host of things in the car. So diagnosing gas and air leaks is a major task for car service technicians. The use of smoke machines is, therefore, essential in diagnosing leak problems of all modern cars.

A typical smoke leak test uses artificial smoke. The mechanic injects and measures this smoke by a smoke machine. The cost of a truly dependable smoke machine is beyond the reach of an average individual. But they are accessible in most professional car services and garages.

Professionals infuse the smoke into the car’s vacuum systems with minor pressure in the smoke testing process. If you see smoke visibly escaping in one of the vacuum systems, a leak is likely present. Most car services typically use gray smoke. Mechanics may opt to use other colors to make the smoke more visible.

Basic Features of a Smoke Testing Machine

A typical smoke machine has the following components and features:

1. They produce smoke.

2. They are able to completely seal the system.

3. There is a pressure gauge that indicates output pressure in psi (pounds per square inch).

4. The output pressure of the machine ranges from 1 to 43 psi.

5. There is a flow meter.

The most basic smoke test for car vacuum systems is to induce smoke inside. Mechanic commonly does this in exhaust systems and intake manifolds. If there is a need to test the evaporative system, mechanics use the pressure gauge and the flow meter since they are very sensitive to even the tiniest of leaks.

How a Car Smoke Test for Leaks Is Performed

While it is a professional car mechanic’s tool, using the smoke machine is really very simple. Rubber and plastic hoses connect the vacuum systems. The majority of leaks are in these hoses and their vacuum fittings because they break down as the car ages. Here’s how to do a smoke test on a car:

1. Seal or plug any obvious potential ports or openings in the intake manifold (or whatever vacuum system you are testing). Start with the inlet down to the throttle body from the air filter or cleaner.

2. Connect the nozzle of the smoke testing machine to the manifold. A good place to connect is the big-diameter vacuum line going to the brake booster.

3. Seal the air filter or cleaner by wrapping it in clingy plastic food wrap. An alternate way is to plug the circular rubber duct located near the throttle body. After performing the smoke leak test, don’t forget to unwrap whatever inlet that you have plugged. If you forget this step, your car won’t start.

4. Hit the smoke button of the smoke testing machine. Allow the smoke a few minutes to saturate the intake tract. If smoke comes out of the oil-fill port, it means there could be a problem in the engine’s crankcase vent system.

Refer to the car operator’s manual and check if the PCV valve is a check valve. Or perform some other method of measuring vacuum manifold into the crankcase. Use a nice bright flashlight to scan the engine compartment for any trace of smoke.

5. Air can leak into the exhaust system by way of a leaking cracked header or manifold gasket. This will confuse the oxygen sensors. To check if this is an issue, fill the exhaust with smoke. You need to be aware that a leak will introduce a good amount of air without producing noticeable noise in the exhaust system.

How Long Is a Car Smoke Leak Test?

Since mechanics need to check three vacuum systems, you can expect that it will take some time to execute a complete smoke leak test. The approximate completion time could be somewhere between 30 to 60 minutes. That is only the duration of the smoke tests.

If several leaks were found upon doing the tests, you should be prepared to fix those leaks as soon as possible. Repairing these leaks will take time, depending on the severity of those leaks. The point is: you need to fix these leaks ASAP for your safety.

how to do a smoke test on car

How Much Will It Cost to Test and Fix Vacuum Leaks?

On average, a diagnostic smoke test costs $89.99. This cost does not include repairs if leaks are discovered. If you want to buy a smoke machine, some units range from $150 to $800.

The EVAP (Evaporative Emission Control) system of your car is designed to store and dispose of the fuel’s vapor that builds up in the fuel system. This prevents the fuel’s vapor from escaping and polluting the atmosphere.

Any breakdown in the system will result in driving problems. To check the system for leaks, EVAP smoke testers are used. The cost of an EVAP test can be anywhere between $60 and $150.

If EVAP issues are discovered in the test, naturally, they have to be fixed. On average, the cost of repairing an EVAP system is $150. If you need replacement parts, it will cost an additional $150 to $440.

We’ve answered the questions: “What is a smoke test – car leak test?; also “How to smoke test a car?; and “Smoke leak test for car cost?”. Next, let’s see how you would know if you need a smoke leak test.

How Do You Know If You Need a Smoke Leak Test?

You will know if your car needs a smoke leak test if you are experiencing the following symptoms:

1. Hissing sound emanating from the engine section while the car is running.

2. Check Engine light comes on and remains lighted while you are driving.

3. Problems or difficulties in acceleration where the car seems to be sluggish and slow to respond.

4. Idling speed that is faster than normal.

5. Loss of engine power where your car does not accelerate as before.

6. Degrading fuel efficiency, where you notice that you have been consuming more fuel than before with the same mileage that you are traveling.

7. Old, cracked, or damaged vacuum lines or hoses. These hoses are made of rubber or plastic. Over time they grow old and lose their vitality. They crack, chip, and develop small pin holes where air and gases may leak.

Driving with a vacuum leak is very dangerous. The leaks may increase, and your safety is at stake. Once you observed any of these signs as you drive, go to your respected mechanic and have your car checked and repaired for leaks.

How to Avoid Vacuum Leaks?

While vacuum leaks are dangerous, they can be prevented. The very basic maintenance that will prevent such problems is the regular look over all the car’s vacuum lines. Vacuum leaks are quite difficult to find.

If you are diligent in inspecting these hoses regularly, you will avoid vacuum leaks and attendant repair costs. Replace those damaged hoses and tubes before they develop cracks and leaks.

Conclusion: Smoke Test for Car Cost and How to Test

So, to recap, what is a smoke leak test on a car? A smoke leak test provides information on leaks present in a car. The car’s vacuum systems will be tested using a smoke machine. Smoke is pumped into the pipes, and any holes it comes out of shows where there are leaks.

How much do smoke leak tests for cars cost? A smoke car leak test costs about $89.99. If you do the test yourself, smoke machines range from $150 to $800. Several smoke tests are done to determine if there are air and gas leaks under the hood of a vehicle.

Upon completing this test, you will know if there is any leak in the piping of the vehicle’s vacuum systems. With the information above, you should now know what a car leak test is and its importance in maximizing your car’s efficiency.