The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

Please Support STM Tuned
Please Support STM Tuned

Boost leak test how to with tester

My reasons for doing this write-up are two fold.
My first reason is to review the boost leak tester and then explain how to use it.

Boost Pro: boost leak tester w/gauge review:

You must be logged in to view this image or video.

When ordering the tester you are giving an option for models with a guage or without. The unguaged model is $12 whereas the gauged model is $17. I choose the gauged model because it is so much more convienent not having to run around to look at my A pillar or having some in the car watching the gauge. Shipping was fast and the tester was well packaged. The tester is 3 inches in diamiter and about 1/2 thick made of sturdy black plastic. The schrader valve as well as the gauge are pre installed so that the tester is ready to go right out of the box. This is the only boost leak tester that I have seen for sale that is this proffesional looking. The price of both models is comprable to what one would pay to make their own tester out of plumbing peices but the look, feel and quality of the boost pro unit is top notch.

How to: Boost leak test using the Boost Pro: Boost leak tester: (note: this test was done on a 1g with a T04B running Maft translator in blow through mode.)
Warning: Only pressurize your intake to the amount of boost you run/ plan to run. If you over pressurize your intake tract damage may occur.

Tools Needed:
Screwdriver: Phillips or Flat head depending upon your hose clamps
Pliers: Bov return line clamp
Socket wrench
Socket set
Air compressor/Gas station

Others peices needed:
Oty. 1: Coupler to connect the boost leak tester to the turbo inlet. The Boost Pro unit is 3in in diameter so depending on your turbo size you will need a 3 x ( X ) coupler. If you're running a TO4B or TO4E you just need a 3 x 3 coupler. You will need to measure your turbo inlet to figure out what size coupler you will need.
Qty. 2 : Hose clamps/ T-bolt clamps. You will need 2 hose/ t-bolt clamps. One clamp needs to be at least 3in in diameter and the other depends on your turbo inlet size.

Step 1. Remove Intake/Air Box.
A. You will need to remove your stock air box and MAF, The air box is bolted in with 3 10mm bolts. Unplug your MAF and loosen the hose clamp on the intake pipe holding the MAF in place. Now the air box and MAF can be removed.
B. Remove the BOV return hose and PCV valve hose.
C. Loosen the hose clamp that holds the intake pipe to the turbo and remove the intake pipe.

You must be logged in to view this image or video.

Step 2. Install coupler & hose clamps on the Boost Pro: boost leak tester.
A. It may take a small amount of elbow grease to get the coupler to fit over the tester
B. Once you have the coupler where you want it put a hose clamp on where the coupler and boost leak tester overlap to hold the tester in place when you pressureize the intake.

You must be logged in to view this image or video.

Step 3. Install the boost leak tester along with coupler and hose clamps onto the turbo inlet. Make sure that both clamps are tight.

You must be logged in to view this image or video.

Step 4. Pressureize the Intake Track:
A. Get out your air compressor (make sure you have the fitting that you use for inflating tires on) and simply place the hose from the air compressor onto the schrader valve of the boost leak test.
B. Watch the gauge on the boost leak tester so you don't over pressureize.
C. Once you reach your desired pressure remove the air hose and listen for leaks.

You must be logged in to view this image or video.

Step 5. Fix leaks and re test

Step 6. Uninstall tester and reinstall your intake pipe, MAF (remember to plug it in) & Air Box, BOV return line and PCV line.


  • boost leak tester 1.JPG
    boost leak tester 1.JPG
    41.3 KB · Views: 94,433
  • boost leak tester 2.JPG
    boost leak tester 2.JPG
    34.4 KB · Views: 41,037
  • boost leak tester 3.JPG
    boost leak tester 3.JPG
    54.6 KB · Views: 86,641
  • boost leak tester 5.JPG
    boost leak tester 5.JPG
    58.8 KB · Views: 110,255
  • boost leak tester 6.JPG
    boost leak tester 6.JPG
    40.5 KB · Views: 85,405


DSM Wiseman
Jun 21, 2003
Dayton, New_Jersey

Step 1B : Remove the BOV return hose and PCV valve hose.

This step is not to be followed, I have had several members asking me about this.

1. Removing the BOV line will result in an opened BOV during the test once the intake pressure is higher than the BOV spring pressure.

2. Removing the PCV line will exclude the PCV valve from the test, the PCV valve is a known leak, instead, open the oil cap and listen for leaks in the crankcase and then remove the PCV line as part of the troubleshooting/process of elimination for crankcase leaks.

Here is something I posted in the past.

1. Disable your mbc.

2. Turn your motor to 30* ATDC to avoid valve overlap.

3. Start your test at the TB elbow and focus on area behind the TB first.

4. Spray soapy water at TB gasket, BISS, TB shaft on both sides, IM gasket, injector insulators, brake booster, afpr and all vacuum lines/connections.

5. Open your oil cap and listen for leaks. (PCV, valve seals/guide, rings)

5. Listen to your tailpipe for leaks. (EGR, valve overlap, jumped timing, bent/unseated valves)

6. Once all leaks are fixed, move the tester back to the turbo inlet.

7. Spray down the compressor cover (known leak), BOV return/flange (DO NOT TAP YOUR BOV LINE FOR YOUR MBC!!!), IC end tank/fins and all connections. Re- test.

8. Note that you will leak air into the crankcase through the turbo seal but do not panic, this is normal during a static pressure test as long as there are no shaft play.

The desired test result from the begining of the LICP (bypassing turbo) is around 20psi (on boost gauge) with the compressor set at 30psi, while taking no less than 30 seconds to bleed down to 0.

As a reference, my last test on my 500 mile new engine, I was able to pressurize the system to 25psi, bled down to about 16psi (my 1G bov) in about 30seconds, then took about 3 mins to 6psi and just kinda lingered there for a while. It's not easy to do but the point is it's possible. My next goal is 30psi After motor break in and Dodge modding my BOV. A boost leak test is one of most pita but important regular maintenace task, the key is patience and endurance


DSM Wiseman
Jun 7, 2003
Minneapolis, Minnesota
Here's a picture of a BLT tester I made from Home Depot, parts for less than $20. I later added a BOV test adapter to fit into it (see pic). For adapter I used a 1 1/4" ID heater hose (Gates 3269S Green Stripe works well), onto a 1 5/16" OD (1" ID) pvc pipe, cemented to a 2 3/8" OD (1 5/16" ID) pvc coupler, 2 hose clamps.

If you're having trouble understanding the "Valves intake-exhaust valve timing turbo" pic shown below, see here:


  • homemade Boost Leak Tester.JPG
    homemade Boost Leak Tester.JPG
    90.1 KB · Views: 3,030
  • Boost leak tester on turbo inlet.JPG
    Boost leak tester on turbo inlet.JPG
    122.7 KB · Views: 3,675
  • Boost leak tester on TB.JPG
    Boost leak tester on TB.JPG
    128.7 KB · Views: 1,813
  • Valves intake-exhaust valve timing turbo.jpg
    Valves intake-exhaust valve timing turbo.jpg
    88.6 KB · Views: 132
  • Boost leak tester with BOV test adapter.JPG
    Boost leak tester with BOV test adapter.JPG
    136.9 KB · Views: 120
Last edited:
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications RixRacing RockAuto RTM Racing STM Tuned

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds