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Finding A Boost Leak - B6 Audi A4, 1.8T

Prior Experience: None
Cost: approx. $15
Time: 15 minutes prep, 15 minutes finding the leak

Discuss this mod - Here

Every turbo car will eventually have the problem of a boost leak. This is especially true after you start modifying the car. In my case, my car went from peaking at 21 psi of boost, to only 15 psi of boost. This happened just after I installed my FMIC, so I initially thought I screwed up one of the hose clamps. After searching and searching, I could not find the leak. I decided to build a tool that I can used to pressure test the system with an air compressor. Here's how it is done

SUPPLIES - The only supplies you need is an air compressor and what'ss needed to build the tool (mostly PVC pipe)

B6 Audi A4 - Building Boost Leak Tester  
Material Quantity Price
2 inch PVC elbow 1 $2

Threaded end for 2 inch elbow

1 $2

Screw cap insert

1 $2

1/4 inch air compressor male connector

1 $3

JB weld or PVC sealant

1 $5

The first thing you want to do is drill a hole in the PVC screw cap that is large enough to screw the 1/4 inch, male, air compressor connection into it

  B6 Audi A4 - Building Boost Leak Tester
B6 Audi A4 - Building Boost Leak Tester  

With the hole drilled, mix up some of the JB weld and coat the hole. Go ahead and screw the air compressor connection into it.

Make sure to seal it up really well with the JB weld.


After the cap is finished you need to seal the threaded PVC end into the 2 inch elbow. This is pretty self explanatory.

You will be left with the two parts pictured to the right

  B6 Audi A4 - Building Boost Leak Tester
B6 Audi A4 - Building Boost Leak Tester  

It doesnt take a rocket scientist to figure this out...but the last step it to seal thee two parts above together. And let it dry for 24 hours.


So how the hell do you use this thing to find a leak? Simple...WITH THE CAR OFF!

Remove the air intake duct on the passenger side of the car. This has been done a million times on this site. For more info see the clear corner mod.

You will see the turbo inlet pipe as pictured to the left


B6 Audi A4 - Building Boost Leak Tester

B6 Audi A4 - Building Boost Leak Tester  

Simply undo the hose clamp, and back the turbo inplet pipe off of the MAF .

B6 Audi A4 - Building Boost Leak Tester  

IMPORTANT: In order to perform the pressure test, it is very important that you disconnect the PCV return hose from the TIP. This WAS NOT written in the writeup I was following.....

what happens is that after the system is pressurized, oil comes back down the pcv pipe into the TIP...and hence the will end up with blue smoke in your order to stop this you have to disconnect the check valve for the PCV return line and plug the hole

I used a rubber wine bottle cork and a hose clamp to plug the hole


B6 Audi A4 - Building Boost Leak Tester  

B6 Audi A4 - Building Boost Leak Tester


B6 Audi A4 - Building Boost Leak Tester  

After you have the hose plugged, you have to Insert the pressure tester into the TIP, and clamp it down really good

NOTE: It may be easier to use a socket on the clamp instead of the flat head screw driver. I couldn't get it clamped tighet enough with only the screw driver. (this picture was taken before removed/plugged the PCV return)


With the pressure tester in the TIP, you have to charge the system. To do this, turn your air compressor up to 10 or 12 psi. With the compressor off, connect the air compressor hose to the male adapter on the pressure tester. (Remember...this is with the car OFF.)

With the system charged, you should be able to hear any boost leaks you may have. From here its up to you to find them an fix them. Mine was pretty obvious after using this technique

What you see to the right is my crankcase breather hose. This was the source of my leak, and fortunately for me, the part was recalled for all 2002 a4 1.8T's  

B6 Audi A4 - Building Boost Leak Tester

Good Luck!

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