6 Symptoms of a Boost Leak and How to Find it

It is important to fix a boost leak as fast as possible because it can damage the turbocharger. Here are the most common signs to look for.

Symptoms Of A Boost Leak

Does your car feels slower than usual, and do you have a check engine light flashing on your dashboard? There is a big risk that your car suffers from a boost leak.

A boost leak can result in many different strange symptoms. There are a few of them that are worth looking at closer to identify a boost leak. But what is a boost leak, and what are the most common symptoms of one?

The most common symptoms of a boost leak are loss of power and a check engine light on the dashboard. You may also notice signs like slow turbo spool, poor fuel economy, and black smoke coming from the exhaust pipe during acceleration.

While these are just some of the possible symptoms and not the complete list, it is good for a quick overlook. Here is a more detailed list of the 6 most common symptoms of a boost leak.

Boost Leak Symptoms

1. Slow Turbo Spool

Turbo Spool

The turbo works by increasing the amount of air and fuel that can be fit into a cylinder; thus, increasing horsepower and performance. However, before the turbo ‘kicks in,’ it’s turbine needs to spin very fast. Until that happens, the turbo does not play a role in boosting the car.

This issue, usually called turbo lag, is when the turbo spools air and fuel to send into the cylinder. If this process is slower than usual, you are experiencing a boost leak. The concept is simple; due to a leak, it takes more time for a turbo to fill up the boost pipes.

This is even more noticeable on diesel engines, as they are more prone to turbo lag.

2. Loss of Power

Slow Car Acceleration

While you are accelerating, the turbo builds pressure in the boost pipes to give the car higher performance. If there is a boost leak, it will take longer to fill these pipes with pressure, and the pressure will be lower than usual.

This will cause a drastic loss of power in your car engine. If the leak is big, it can even mean that you lose all turbo pressure.

3. Check Engine Light

Check Engine Light On Dashboard E1609869927250

The check engine light monitors all sensors of a car engine, including the boost pressure sensor.

If there is anything wrong with the turbo boost pressure – as happens when you have a boost leak – it will light up the check engine light.

If you see a check engine light on your dashboard, check the trouble codes with an OBD2 scanner.

4. Black Smoke from the Exhaust

Black Smoke From Exhaust

The MAF sensor measures the air going into the engine. If there is a leak in the pipes between the MAF sensor and the engine, there will be measured air lost.

This will cause a wrong air-fuel mixture and, in most cases, a rich mixture. A too-rich mixture will cause black smoke from the exhaust pipe. So if you experience black smoke from the exhaust when accelerating, it is definitely time to check for any boost leaks.

5. Poor Fuel Economy

Fuel Consumption

The same thing applies to the fuel consumption of the boost leak and the measurement of the MAF sensor.

This might not be distinguishable very easily, but if you keep an eye on your car’s average fuel consumption, you will catch a boost leak easily.

If the car is consuming more fuel than it should, you have a problem. A boost leak test can prove to be helpful in such situations.

6. Poor Idling

Car Engine Rough Idle

This only holds if you have a car with a mass airflow sensor or MAS/MAF. The MAF senses the amount of air leaving the turbo and entering the engine.

If there is a big boost leak, your car will have problems idling perfectly. It might stall and shut down as a result of the leak.

It is not very common to have a poor idle because of a boost pipe leak, though it can happen if the leak is large. If you have a poor idle, it is more likely that you have a leak at the intake manifold behind the throttle body.

What is a boost leak?

Boost Pipes

A boost leak is a type of air leak in the intake path just before the engine cylinders. It is basically a loose clamp or damaged hose that cannot handle the turbo boost’s pressure.

Ignoring a boost leak will eventually reduce your turbo’s life and, in turn, the car engine’s life.

The ECU determines the ratio of fuel to air; however, if there is leakage of air along the way, the ratio is incorrectly calculated.

Diesel engines are accommodating in this regard, as they are more tolerant of a high fuel to air ratio. However, petrol engines are sensitive. Therefore, a boost leak inspection is necessary for your car’s optimal performance.

How to Find a Boost Leak

Smoke Machine Testing

To find a boost leak easily, you should use an EVAP smoke machine. With this type of device, you will find boost leaks in no time.

The machine pressurizes the boost pipes with smoke, and if there is smoke coming from somewhere in the engine bay, you most likely have a boost leak there.

If you have a small workshop, it is definitely time to invest in one. You can see my recommendations for EVAP smoke machines here: Best EVAP smoke machines.

The hard way to find a boost leak is by trying to find it visually. Check all the boost pipes and hoses to make sure that none of them came loose.

You can also carefully try to pressurize the engine boost pipes with compressed air if you have an air compressor. Be very careful, though, because engines run very well on pressurized air!! Ensure the wheels are in the air so they won’t start going forward because of the pressurized air, and be very careful with the pressure.

Magnus Sellén
Written by:

Magnus is the owner and main author of Mechanicbase. He has been working as a car mechanic for over 10 years, and the majority of them specialized in advanced car diagnostics and troubleshooting. Certified Automotive Diagnostic Technician.

Related Posts