turbo pipe leak

Boost Leak Symptoms & The Causes

In Engine by Magnus Sellén14 Comments

Is your ‘check engine light‘ flashing on your dashboard and does the engine’s power suddenly feels reduced?

Then your car engine might have put itself into Limp-Mode and the issue should be fixed as fast as possible. Boost leaks can damage your turbocharger and your engine, which may result in even higher repair costs.

In this article, you will get all the information on how to detect and repair a boost leak and finally get your car’s full performance back. Let’s begin!

turbo boost leak

Boost Leak Information

A boost leak is a type of air leak that happens in the intake path just before the engine cylinders. It is basically a loose clamp that cannot handle the pressure from the boost.

Engines that have turbo are more prone to a boost/intake leak compared to non-turbo engines, because of the added numbers of pipes and hoses joining the turbo with the engine equipment and the pressure that a turbo gives. These hoses and pipes are directly exposed to the heat inside an engine bay, which can cause cracks in them and lead to leaks.

Sometimes, leaks in a pipe can happen due to a loose engine mount, which can twist a pipe simply with torque. Although loss of power is not harmful – except if you are in a race – it can become harmful if neglected for a long time.

Ignoring a boost leak will eventually reduce your turbo’s life and in turn the car engine’s life. Understanding the workings of a turbo is easy as there are two components at work; fuel and air. The car’s engine works on a mixture of fuel and air.

The ECU determines the ratio of fuel to air; however, if there is leakage of air along the way, the ratio is incorrectly calculated causing your car’s turbo to work harder than usual. 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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Signs of a Boost Leak

A boost leak can result in a lot of different symptoms. There are a few of them that are worth looking closer at to identify a boost leak. Here are the most common symptoms:

1. Slow Spool

turbo boost leak

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 spin at maximum capacity.

2. Loss of Power

While you are accelerating, the turbo is giving a boost to the engine, motivating it to perform faster and better. If there is a boost leak, you will feel a sudden loss of power during acceleration.

3. Check Engine Light

If you have a boost leak on your car, you will most likely get a flashing check engine light on your dashboard. If your check engine light is flashing, the best method is to read the trouble codes with an OBD Scanner.

4. Poor Idling

This only holds true if you have a car with a mass air flow sensor or MAS/MAF. The MAF senses the amount of air leaving the turbo and entering the engine. If there is a boost leak – which usually happens in the MAF area – your car will have problems idling perfectly. It might stall, and close down as a result of the leak.

5. Inconsistent Timing

Your engine tuning will go awry as soon as you have a boost leak. Therefore, any inconsistent sound in your engine is basically due to a boost leak.

6. Excess Smoke from the Exhaust

The inconsistent working of a turbo will disturb the process inside the engine cylinders. More than the usual amount of fuel will be used and you will see more than the usual amount of smoke coming out of your exhaust.

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7. Poor Economy

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.

Problem Symptoms Causes Solutions
Boost leak symptoms Low acceleration

Check engine light

Rough Idle

Black smoke from exhaust on acceleration

Poor fuel economy
Faulty Boost pressure pipes

Faulty Intake Plenum

Faulty vacuum hoses
Replace/Repair the boost leak

How to Find a Boost Leak

The easiest way to find a boost leak is to use an EVAP smoke machine but you can also use compressed air or in some rare cases – visually inspect the boost pipes and hoses. Here are some tips on how to find a boost leak.

1. Check Clamps & Couplers

A boost leak can happen where there are clamps, so it is natural to look for leaks in all the couplers and clamps connecting the turbo to the engine. Maybe a clamp was not properly tightened or it was left loose after you made the previous modification to your turbocharger.

To start your inspection, first take a look at the compressor housing, move towards the vacuum lines next, and work your way to the wastegate controller. Check all the clamps on the way and ensure they are tight and in place and also check for any scratches or cuts to the housing.

2. Use a Boost Leak Tester/compressed air

Still couldn’t find out anything? No worries, some brilliant minds have invented a device called the boost leak tester. This device does exactly what it is supposed to; it tests leaks for you, so you don’t have to. This is a great tool for anybody who is not experienced in car work and also for those of you who don’t want to spend money taking their car to the nearest mechanical workshop. Therefore, if you can afford one, you can save some precious time.

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Using a boost leak tester, you don’t need to start up the car or need to charge up the turbo. In fact, the machine does all the work by itself by pressurizing the system just like a turbo spool. All you need to do is remove the turbo inlet and attach the tester in its place. Alternatively, attach an air compressor to the system and watch the machine build pressure. Now, simply listen for air leakages and mark them.

Boost leak testers are a surprisingly cheap and a necessary tool for every turbo car owner.

You can also go to a mechanic workshop and use their boost leak tester for a small penny.

Check out the adapter at Amazon here Torque Solution TS-BLT-BILLET Boost Leak Tester Universalir?t=askamastermec 20&l=am2&o=1&a=B014M1LWC2 and make sure it fit your pipes. The only thing you need for this tool is compressed air.

You can also use an EVAP smoke machine to find any boost leaks easily.

Repairing a Boost Leak

Once you have found the leak, it is time to patch it up. As we have learned from the information above, leaks are usually found in untightened clamps or couplers. Start off by tightening them up and then checking again until you find all the leakages. If you need help, hire a mechanic but the thing about mechanics is they charge quite a high price for such easy work. Keep in mind a bill of about $100, give or take, if you choose to go for a mechainic.

14 thoughts on “ Boost Leak Symptoms & The Causes ”

  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.

  10. Due to very high demand and a high amount of comments, you might have trouble getting your comment answered by me. If you want to get fast answers from a certified automotive technician you should ask your questions here: Ask A Mechanic

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