Boost leak test instructions - Page 2
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This is a discussion on Boost leak test instructions within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Originally Posted by lundholm08 I did Donkey :-) I've been scouring NASIOC and the rest of the internet to see ...

  1. #16
    Moderator Donkey's Avatar
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    Apr 2005
    Da boonies,Va
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    Quote Originally Posted by lundholm08 View Post
    I did Donkey :-) I've been scouring NASIOC and the rest of the internet to see if I can see a step by step walkthrough if you will. I'm all kinds of nervous about potentially blowing my valves/heads/etc... and the inlet hose has 4 ports, not 3, so I'm wondering what to plug?
    Jebus dude.......then plug them all.How hard is that?Seriously,slow down and use some common sense.Not to mention how are you going to blow your valves and head?You only need to use maybe 20-25psi for the test.Most cyclinders have 140-160psi worth of compression pressure..................
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  3. #17
    Registered User Black X Dahlia's Avatar
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    Quote Originally Posted by lundholm08 View Post
    Do you happen to have any pics of the PCV valve plugged? What I mean to ask is, I know to plug the PCV valve nipple on the inlet hose, but what about the line you popped off the nipple, do you plug that as well or just leave it hanging there until you're done?
    did you plug both nipples coming off the air intake and the intak manifold? If so then the rubber line on the pcv valve that is unused....just take it off and place it somewhere you can find it so you doesnt come off or something while your testing and fall into the flat four engine bay (aka cluster**** forest)
    How Fast Can You Afford To Go?

  4. #18
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    Jun 2009
    What a coincidence that nice boost leak tester you put together there looks identical to the DFCustoms boose leak testers on ebay that I sell.

    Im not suprised, but all I ask is to give credit where its due.

    I have been making boost leak testers for years. If anyone wants some boost leak testers with different options (tire valve stem, 0-30 psi gauge, 3" to go over the plastic intake pipe) send me an email at huth1913 @ hotmail . com or go on and use key word "Boost Leak Testers"

    Word from the wise, dont forget to remove your oil cap or the air pressure will build up in your valve cover and blow out your cam seals. It happens.


    Quote Originally Posted by Black X Dahlia View Post
    i searched the forums and couldnt find any posts about instructions on performing a boost leak test, so i thought id post one showing everyone how i performed the leak test on my own car.

    Items Needed:
    2" PVC Cap
    2" Double Sided Rubber Coupling (2" on both ends)
    Valve Stem
    Air Quick Connection (Female)
    Air Regulator (It's not needed, but makes the process MUCH safer)
    Rubber Plugs
    Air Compressor
    Screw Driver
    Boost Gauge (optional but very handy)

    Here is an example of the finished product. (I put the hose for extra play in the tight area of the engine bay, i had the extra time at work.)

    I forgot to take pics while actually performing the leak test so these will have to work, haha.


    1.) Remove Intake Elbow, and the intake box for some extra room. (if your going to be monitoring the air pressure in your engine via boost gauge then do not unplug your mass air flow sensor when removing the intake box. And if your not going to be using a boost gauge then disconnect your battery cables FIRST, THEN remove your mass air flow sensor.)

    2.) Remove rubber line on your intake that is connected to the purge valve(your purge valve is the black circular object located directly to the left of your alternator), and plug the nipple on your intake with any type of plug (i used rubber vaccum caps).

    3.)Remove rubber line that is connected to the BACK of the purge valve...this line leads to the intake manifold. Plug the metal nipple coming off the intake manifold, and make sure your plugs are secure. If you do not remove the purge valve when performing the leak test, then it will make a buzzing sound, which could damage the seats of the valve and ruin it.

    4.) Install 2" coupling to the intake, and make sure it is secure. Instead of trying to fit clamps on my plugs and couplings, i decided to put zip ties on the end of them to make everything somewhat easier.

    5.) Hook up regulator and air compressor to the valve stem on the pvc cap, and turn air compressor on. Slowly let air in with the regulator, and get someone to watch the boost gauge to keep an eye on how much air pressure is in the engine. Be very careful not to put too much air in your engine, as you can damage components. Keep the psi a little higher than what you normally run. For instance, if your going to be running around 15psi...then pump about 17-18psi. Many ppl suggest that you do not exceed 20psi unless you run this amount of psi normally.

    Now just listen and spray soap and water on flanges, hoses, intercooler, ect...

    Here's some more pics to help out along the way.

    Caps i use for plugs

    After performing the leak test, i found a HUGE leak at the manifold where i am leaking over half the amount of boost i am suuposed to be making. Going to replace gasket and see what happens.

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  6. #19
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    Feb 2010
    What is the inside diameter of those caps, i may have to order some online.

  7. #20
    Registered User 2:43AM's Avatar
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    Sep 2008
    Just reading through this thread since I am about to do the test myself on my WRX, and I noticed that the OP removed and plugged the connection from the manifold to the purge value. I don't see why. The backside of the purge valve would in fact see pressure in the manifold during normal operation. Removing it from the equation would remove a possible failed/leaking purge valve from the test procedure.

    And for further clarification, if you wanted to be doubly sure you weren't over-pressurizing your crankcase, you would simply remove and cap the nipple on the inlet that connects to the PCV (rear, side of inlet tube) and the nipple (lower front, side of inlet) that connects to the crankcase blowby hose, i.e. the one that spans across the TMIC.

    Word up.

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