A check engine light on the board accompanied by P0440, P0442, P0445, P0446, or P0411 typically indicates a problem with the car’s evaporative emission control system (EVAP).
This issue is generally a leak that can be detected through a smoke test.
However, this test can also be performed on other vehicle systems, such as the exhaust, brake booster, or HVAC, to detect gas or vacuum leaks.
The average cost of a car smoke test varies from $45 to $130, depending on the system being tested. EVAP smoke tests cost around $107 on average. Smoke tests are also done to detect leaks in the exhaust and PCV systems, as well as other vacuum systems of the car. Additional diagnostic tests, if required, can bump the costs up to $627 or more.
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Smoke Testing A Car Costs*
A smoke test is a handy and inexpensive diagnostic method originally developed to detect leaks in a vehicle’s EVAP system.
This system equips all gasoline vehicles manufactured after the 1970s and is used to prevent gasoline vapors formed in the fuel system from escaping into the atmosphere.
In modern cars, the vehicle’s computer can detect leaks in the system and signal them by turning on the check engine light on the board and showing a OBD-II code – the actual code can vary from car make to car make, but it generally is P0445 or P0446.
A smoke test can identify where in the EVAP system the leak occurs and whether it is a tiny hole or a larger damage.
On average, mechanics charge between $90 and $127 to perform a smoke test on the EVAP system.
In a similar fashion, the smoke test can be used to detect leaks in other car systems.
The table below shows a comparison of average car smoke test costs for various car systems*:
| Car System | Average Smoke Test Cost |
|---|---|
| EVAP system | $90 - $127 |
| PCV system | $55 - $100 |
| Intake manifold | $65 - $110 |
| Fluid reservoirs | $35 - $65 |
| Injector seal | $70 - $105 |
| Exhaust system | $80 - $120 |
| Brake booster | $85 - $130 |
| Valves and pistons | $70 - $120 |
| Transmission | $90 - $160 |
| HVAC system | $80 - $125 |
*Average prices in the table were calculated based on quotes received from various independent contractors and dealerships across the nation. They are correct as of October 2022 and intended to use as reference only.
5 Car Smoke Test Price Factors To Consider
A car smoke test is a fairly inexpensive diagnostic method, but the final price can vary based on different factors.
The table below shows a breakdown of costs your mechanic could charge*:
| Factor | Average Smoke Test Price |
|---|---|
| System being tested | $35 - $130 |
| Small leak detection | $0 - $100 |
| Additional diagnostic tests | $0 - $500 |
| Total costs | $35 - $730 |
*Average prices in the table were calculated based on quotes received from independent mechanics and dealerships. They are correct as of October 2022 and intended to use as reference only.
1. System Being Tested
The main factor influencing the car smoke test cost is the system being tested.
This test is routinely used to detect vapor leaks in the EVAP system, but mechanics often employ the same method to detect other air, emissions, and even fluid leaks.
EVAP System
A car’s EVAP system transfers fuel vapors formed in the fuel tank and engine into a charcoal canister through a tube. The charcoal canister captures these harmful vapors and prevents them from entering the atmosphere.
The tube and canister are equipped with vent and purge valves that keep vapors trapped within the system.
When working correctly, the EVAP system can increase the fuel mileage.
However, EVAP problems are common. The valves can break or the tube can get punctured. Leaks can happen anywhere in the system, and a smoke test can indicate the culprit.
Average prices for an EVAP smoke test vary from $90 to $127.
PCV System
The positive crankcase ventilation (PCV) system consists of valves and hoses that connect the engine crankshaft to the intake manifold, enabling the lower half of the engine to release pressure and gases when operating.
Gases sucked by the intake manifold, which is constantly under vacuum, are then returned to the engine and burned as fuel.
A bad PCV system could cause rough idling, engine oil leaks, lack of power, and the engine burning oil. PCV gas leaks can be detected through a smoke test that costs $55 to $100, on average.
Intake Manifold
The intake manifold is connected to the PCV system, but it often needs a separate diagnostic.
As explained, this part’s role is to capture the gases from the PCV system and return them to the engine for combustion.
Intake manifold smoke test costs vary from $65 to $110 on average. Mechanics often charge more if they have to test both the PCV system and intake manifold, with some summing up the costs for each separate service.
Thus, the final smoke test for both systems could cost you between $120 and $220.
Fluid Reservoirs
Fluid reservoirs are plastic tanks that contain various vehicle fluids. A standard car has tanks for the transmission fluid, fuel, coolant, power steering fluid, brake fluid, and windshield wiper fluid.
Over time, the plastic in these tanks can become brittle and crack. Metal tanks that equip some makes and models are subject to corrosion, and they could also start to leak.
Caps and valves can become faulty and leak too. Fluid leaks are often easier to fix than gas leaks, but the hole can sometimes be so tiny that it isn’t clear where the fluid comes out from.
In these instances, mechanics could drain the fluid in the tank and use a smoke test to find the hole.
Fluid reservoir smoke tests are the cheapest, costing between $35 and $65 on average.
Injector Seal
Fuel injector seals are located on each end of the fuel injectors. Their role is to provide an airtight seal with the engine.
When broken, they could lead to fuel or engine vacuum leaks, which could in turn result in a drop in performance.
Smoke tests to detect injector seal leaks cost between $70 and $105 on average, depending on how many fuel injectors (cylinders) the car has.
Exhaust System
The exhaust’s function is pretty self-explanatory. This system transports combustion fumes from the engine to the outside through the exhaust pipe.
Leaks generally occur at the exhaust manifold gasket, but holes or leaks can happen anywhere else in the system, too.
A sign of exhaust leak is a lingering smell of burnt in the cabin. Smoke tests to detect the leakage cost $80 to 120 on average.
Brake Booster
Also known as brake servo, the brake booster uses hydraulic or vacuum pressure to assist the driver when braking.
Its role is to multiply the force applied to the brake pedal and increase the master cylinder force, enabling the driver to stop the car effectively even when pressing the brake pedal gently.
If this system fails, the driver has to apply a much greater pressure on the pedal. In some cases, the brakes may even become unresponsive, regardless of the amount of pressure applied.
Vacuum brake boosters are much more common than hydraulic ones, and vacuum leaks are the main type of failure.
Leaks are usually signaled by the board computer as OBD codes (typically P0558). The check engine light may also illuminate on the dashboard.
Other symptoms include engine idling, a hard-to-start engine, and poor fuel mileage.
Brake booster vacuum leaks can be detected through a smoke test which has a median cost of $85 to $130.
Valves and Pistons
A smoke test is not the most common choice for detecting leaks in valves and pistons. These components usually move the fuel, and leaks are typically detected with a compression test.
However, if this test can’t identify the source of the problem – whether it’s the piston or intake or exhaust valve – the only cost-effective alternative to detect the culprit is a smoke test.
Mechanics generally connect the smoke machine to the spark plug and pump the smoke into the system.
If it comes out from the oil filter cap, the problem is in the rings or pistons. Smoke visible from the intake or exhaust indicates a problem with the respective valve.
Depending on your location and actual time to detect the leak, a valve and pistons smoke test can cost from $70 to $120 on average.
Transmission
Similar to valves and pistons, the car transmission is filled with hydraulic fluid.
Leaks are generally easy to spot under the car (transmission fluid is typically dark red in color), and a mechanic can confirm them by checking the fluid level at a day or two after a transmission fluid change.
Typically, transmission leaks happen due to a worn pan gasket. However, the pan might have a fine crack that is not as easy to detect.
Leaks could also happen in the tubes that transport the fluid to the torque converter, or even in the torque converter.
If the leak source can’t be detected through other diagnostic methods, a smoke test can be performed once the fluid has been drained out.
A transmission smoke test is generally more expensive than testing other systems, costing between $90 and $160 on average.
HVAC System
A car’s HVAC (or AC) is another system that uses vacuum to move the air through the system and remove moisture, oxides, and debris from the air in the cabin.
Like most other systems, the HVAC leak can happen anywhere in the system. A smoke test is the simplest method to find it.
The test costs $80 to $125 on average.
2. Leak Severity
The second factor that determines a car’s smoke test price is the severity of the leak.
Smoke can escape easily if the leak hole is large. Your mechanic will be able to detect it in a matter of minutes, reducing labor time, and thus, lowering the costs.
Things are the complete opposite if the leak is small.
Even if smoke machines generate milky white smoke that is dense and easy to spot, spotting it when coming out of a tiny hole is often challenging. This could prolong diagnostic time.
Mechanics could also decide to run alternative diagnostic tests to make sure they have found the real culprit.
Not only will you have to pay more for labor, but you might also have to pay for additional diagnostics.
3. Car Make & Model
Smoke tests are performed in the same way on all cars, so the make and model shouldn’t have an impact on costs.
However, the type of car you drive could influence your choice of mechanic.
Independent mechanics are generally experienced in servicing frugal family and city cars, trucks, and SUVs. However, they may not have experience with imported cars.
Owners of luxury vehicles may not feel confident enough in taking their car to an independent mechanic, preferring a dealership instead.
Dealerships almost always charge higher labor rates compared to independent shops, and the smoke test could cost more when performed by an authorized mechanic.
4. Location
Another factor influencing labor rates – and, thus, the cost of a smoke test – is your location.
The average national rate mechanics charge falls in the $90 to $150 per hour range. However, prices vary widely based on location.
Mechanics in Michigan, for instance, often charge below the national average.
Those in California or New York charge higher rates that could exceed the national average. Texas is another expensive state – owners can expect a smoke test in the state to cost around $255.
5. Additional Diagnostic Tests
As explained, small leaks are often difficult to detect through a smoke test. To narrow down the possibilities, mechanics may run a computer diagnostic test.
This test is done based on OBD codes signaled by your car and typically costs between $88 and $110. However, costs could skyrocket in the case of imported vehicles. In this case, a diagnostic can set you back up to $500.
How Long Does It Take To Perform A Smoke Test?
A smoke test can take between 15 and 60 minutes, depending on the system being tested and leak size. Large leaks are easier and faster to detect.
However, when calculating labor time, you should also consider additional steps mechanics must perform before running the smoke test.
This test is seamless to run on vacuum systems, as the air can flow freely through these tubes. Additional steps must be taken when testing a hydraulic or fuel system.
In this case, the mechanic must first drain the fluid, perform the smoke test, then replenish the fluid container. Labor time increases, and you also have to pay for the new fluid.
Is A Vacuum Leak Expensive To Fix?
A vacuum leak can be very cheap or ridiculously expensive to fix, depending on what you have to replace.
The table below shows the average prices to fix a vacuum leak*:
| Leak Source | Average Repair Price (Parts + Labor) |
|---|---|
| Leaky valve caps or gaskets | $30 - $50 |
| PCV valve | $78 - $96 |
| Vacuum hose | $100 - $250 |
| Air injection hose | $139 - $1,430 |
| Intake manifold gasket | $556 - $615 |
| Intake manifold | $214 - $270 |
| EGR valve | $351 - $433 |
| Brake booster | $628 - $779 |
*Average prices in the table were calculated based on quotes from independent and dealership mechanics. They are correct as of October 2022 and intended to use as reference only.
Caps and gaskets are the most common causes of vacuum leaks. These fixes are quick and cheap, rarely costing over $50.
Vacuum hoses cost between $70 and $200 on average; including labor, you could spend between $100 and $250.
Replacing an intake manifold gasket costs between $556 and $615 for parts and labor, on average. However, an air injection hose can be as expensive as $1,430, depending on the car’s make and model.
FAQs
How to tell if my car has a vacuum leak?
A check engine warning and OBD code on the dashboard are the main signs of a vacuum leak.
Other telltales include sporadic idling, engine hesitation, and vacuum sounds.
What are the signs of an exhaust leak?
Gas or a burnt smell inside the cabin are the main signals of an exhaust leak.
Other signs include acceleration and power loss, reduced fuel economy, and engine noises.
Can I keep driving a car with emissions light on?
You can still drive the car if the emissions light is on, but only if you can’t smell a gas or burnt smell in the cabin. Even so, it is recommended to drive to the nearer repair center and have the issue fixed.
Not only can emission leaks have a negative impact on your car’s performance, but they can lead to asphyxia.
To End
A car smoke test is generally performed to detect vacuum leaks in the EVAP and PCV systems.
It can also be performed to detect vacuum leaks in other systems and even to find leaks in hydraulic systems.
The median car smoke test price varies between $45 to $130 depending on the system being tested, but could cost over $600 if the car requires further diagnosis.
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