boost dropping

[FLIPTION]

Not sure if this is a boost leak, vacuum leak, or bov issue. When I go WOT, my Greddy RS bov blows off by itself (not fully) and boost drops maybe 2-3psi after it hits 14psi (which is where my MBC is set to) without me letting go of the gas. What could this be? What should the vacuum read during idle?

 

[viprez586]

Boost leak test: compressor, Compressor elbow, BOV flange, TB(dont forget theres 2 gaskets), all hoses and connections, check the intercooler for holes, Biss screw o-ring, Injector seals, and all connections to the intake manifold. Certain places you can use RTV silicone to help seal them. If your BOV is vented REcirculate that!
Vac reading should be 18-20 inhg(typically)

 

[FLIPTION]

but if it was a TRUE leak wouldn't it be doing this ALL the time.. earlier i got on it it was fine.. stayed at 14psi to redline... What's weird also is I had a coolant leak for a few days... thought I found where the leak was (oil cooling tube), bought the part, and all of a sudden the leak stopped.. wtf is going on??

 

[romeen]

Boost leak test

Agreed. That should be the first place to start IMO.

but if it was a TRUE leak wouldn't it be doing this ALL the time.. earlier i got on it it was fine.. stayed at 14psi to redline.

Not necessarily. From personal experience the characteristics of the boost leak can very depending on other variables/conditions. I can't explain why with complete certainty but I suspect it has to do with expansion/contraction, vibrations, etc. affecting joints and seals.

If the BOV is venting during boosting then I would pay particular attention to a possible leak in the vacuum line that runs from the IM to the BOV. If that checks out then it could be from improper adjustment of the tension screw or a faulty spring inside the BOV. Maybe someone who has that particular BOV can lend further insight.