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Help required doing a boost leak test

6977 Views 10 Replies 3 Participants Last post by  Simon
Hi guys,

So I followed the DIY especially the one on naosic :


I can't seem to be able to build pressure and I get air coming out of my oil cap. I pretty much did everything except instead of disconnecting the crankcase breather at the PCV, I disconnected the other end because it was easier to reach...

So basically :

1) Unplugged and capped the two vacuum host on the inlet
2) Capped the pipes that connect to the metal tubing in front of the intercooler (related to the PCV system I think
3) Disconnected the PCV hose and capped both ends (Located it using the crawford air/oil separator install video

Any idea of what step I might be missing ? I have a 2010 STI.

Thanks !
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The only vacuum hose I have left connected is the one right on top of where the BPV reconnect to the intake. I'll trace back where it goes, maybe that's another one that need to be disconnected

Any idea what that is ?

Ok I think this is my problem, it's the PCV hose assembly, following it, it y off with one branch going to the pcv valve and the other one going to the engine. I disconnected and capped the end going to the pcv but I guess air is still going into the other end. I'll see how it can be disconnected from the intake inlet. There seem to be some kind of sensor or valve right at the inlet
Hi guys,

So here is a picture to help :

The DIY included above is a bit misleading for a GR as they mention removing the intercooler to disconnect the crankcase breather from under the throttle body, that's not exactly where it is on our car.

The good news is that I think that just disconnecting the check valve from the inlet can capping it would allow an intake test to be done without removing the intercooler to cap up any hoses sitting under the throttle body.

Now my question, I did pull to try to dislodge the PCV check valve (which I think is that that white thing is called) off the inlet but it was stuck in there pretty good. I didn't have the balls to pull as hard as I could have. Has anybody been sucessful removing it ? If so, what did you remove ? The inlet side or the other side ?

In that video, they seem to remove the other side but the crimp on that cable doesn't really look like it can be re-used besides, the service manual shows the valve and the rubber line as one piece of assembly that comes off so that would suggest that it should come off from the inlet side.

Crawford Performance Air Oil Separator How To Install by Subie TV - YouTube

I tried calling my mom but she was unavailable, any help ?
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I'll trace back where it goes, maybe that's another one that need to be disconnected

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I'll trace back where it goes, maybe that's another one that need to be disconnected Image Link

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Well now that its been established it need to be disconnected, how :)
You guys definitely got the play by play lol. I'll try to write a how to once it's done. At this point I am just looking for something like :

Yup, I have done an intake pressure test on a GR, yank on that white thing with confidence.

Can't believe nobody has done a leak test on a GR. I'd love to get some feedback as I might get back at it today !

I was going through my old threads and noticed you never came back to this one. I know it was a little under 3 years ago, lol, but have you ever figured how to do your leak test and what was the leak?
Hey, I just noticed this. Well, I never was able to pressurize the intake properly, as I didn't want to rip apart the PCV hosing at that time.

What I think was happening was this :


I did have a GR stumble and at the right load, it leaned out and affected my WOT trims. I was able to compensate for it in the load comp table, I also disabled my WOT trims . All my trims are within 2% now and the car runs pretty good !

I think that was the issue
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