Turbo Pipe Leak

Boost Leak Symptoms & How to find it

In Engine by 14 Comments

Is your car feeling much slower than usual, and you have a check engine light on your dashboard?

This may be caused by a boost leak!

But what is a boost leak and what are the most common symptoms of one?

In this article, we will talk about the common symptoms of a boost leak and how you can easily find one.

Top 6 Boost Leak Symptoms

A boost leak can result in a lot of different symptoms. There are a few of them that are worth looking closer to identify a boost leak.

The most common symptoms of a boost leak are a check engine light, slow turbo spool, bad engine performance, and black smoke from the exhaust when accelerating.

Here is a more detailed list of the 6 most common symptoms of a boost leak.

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 the 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.

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2. Loss of Power

Slow Car Acceleration

While you are accelerating, the turbo builds pressure into 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, which will be wrong if 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 on 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 about the boost leak and measurement of the MAF sensor.

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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 close down as a result of the leak.

It is not very common with poor idle because of a boost pipe leak, it is more common if the leak is at the intake manifold behind the throttle body, but it can be true if it is a huge leak.

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.

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How to Find a Boost Leak

Smoke Machine Testing

You can either try to find the boost leak the hard way or the easy way.

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.

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The hard way to find a boost leak is 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 it won’t start going forward because of the pressurized air and be very careful with the pressure.

14 thoughts on “ Boost Leak Symptoms & How to find it ”

  1. Hi i wonder if you can help. I own fiat bravo 1.9 multi jet diesel 2007 model clocking at 95k. I recently started hearing hissing noise from engine. I had local garage man looked at it mentioned turbo inlet hose split but he don’t have parts available immediately. The problem is I have flight to catch in 2 days and I will be struggling with public transport to reach on time. It’s 60 miles one way and will take 90 minutes roughly. Am I still okay to drive?

    1. Author

      I guess you have already made the trip. However if it’s a minor leak you can drive it carefully without boost. If the turbo pipe is leaking and you are pushing the turbo fully, you can overrev it and damage the turbocharger/supercharger.

  2. Just had my turbo replaced now when I start the engine not every time I can go at 10mph after about 50 – 100yards it just goes like a steam train any ideas

  3. Mechanic said it’s the turbo boost pipe split he said about 250 pounds to fix is that cheap

    1. Hi Magnus,

      My name is Lyle, I have a Polo 1.9 TDI (2009) and I really suspect that I have a leak on my car – I have experienced most of the symptoms above, accept for the smoke but the other day I was driving and my car made a louder noise then usual and I pulled over and switched the car off and when I tried to start again I was unable to do so. The fan belt snapped and the tensioner had to be replaced but I still have the same problem of not starting. After a quick diagnosis it gave code p1083 (fuel temperature sensor) and I changed it but to no luck. The Diesel pump still works fine, the big belt is still in place and works well – do you think the leak could be causing the car to not start?

  4. I have a x type jaguar 2.0 diesel 2004 as soon as I pull away there is a loud whistle that comes and goes in conjunction with pressing accelerator and goes when I take my foot off, car drives perfect with no hesitation or lack of power and no lights on dash evident, tiny bit of black smoke for few seconds on morning startup and then none for rest of day, car is in fantastic condition and only done 100,000 miles
    Help please Gary

  5. Hi there, I have been thinking to buy this x-type 2.0d for a long time and this week i got it finally. however there are small issues im facing and i would like to ask some help and insight from you you guys.
    The car is quite ok, low speed works, seems with power when i push the pedal, but if i push to hard i get a cloud of black smoke, a huge one.
    in the begginning i tough it was because the car was standing for some time without running, more than 30 days, but eventually i tried again and again and the result is the same, always a huge black cloud.
    i have looked on the web and i read somewhere that could be the turbo or the some pipe needing some cleaning, but today, and once again testing if this behavior/result was gone, when i pushed the pedal in first gear, shift it to second, both with the foot all down, when the second got release i got the usual power kick but i felt lose of power and yellow light “glow plug check” came up in the dashboard. with this i just start driving ‘normally’ more 200 meters and turn off the engine.
    after 3 minutes i turn it on again, and no light, everything seems as it was.
    any tough to share with me, please?

  6. hi,my 02 uk impreza wrx is really slow to boost(a lot more lag than previous imprezas ive owned)&the aftermarket dumpvalve only hisses when its cold&only in 1st&2nd gear it makes a noise burt goes silent when car is fully warmed up
    no engine lights on,no bad idle but it seems to take ages to build pressure
    any thoughts please

  7. Bmw x5 2012 3.5im sport, jerking during acceleration strangely, sometimes normal, strange whistle sound not normal from regular turbo noise, no codes, completely lost do not want to take it to a dealer

  8. I have 2016 qashqai 1.6 diesel automatic car. How many bars is the pressure inside the turbo hose of this vehicle?
    I ask to find out. What should I do if I have a small crack.

  9. Hi, i have a 2004 audi a4 quattro 1.8 t i keep getting the p0341 code for cam pos. sensor, ive replaced it twice but still get the code, also the crank pos. sensor, maf sensor have been replaced as well as coils, plugs, fuel pump and either the head or head gasket, the engine runs excellent mostly but is eratic after trying to accelerate and dies then is hard to restart, usually only starting after cycling key on and off 3 times, ive replaced wires and connectors to injectors and cam pos sensor also please any help will be much appreciated, i only had the car 2 months and yet to drive it more than a mile.

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