Boost leak test question...

[husterka]

I just performed a boost leak test on my 99gsx and I was only able to hold 10psi. I found a small leak on the greddy BOV (getting some RTV for that tomorrow) and a big leak on the BISS (ordered one tonight). I also noticed a lot of air coming out of the valve cover breather. Should the breather be capped off during the test or do I have an internal leak? There was no mention of capping this off in the VFAQ. Thanks!

 

[Coldandafraid]

air comes out my breather too... dang it

 

[Sephroth57]

is air supposed to come out of the breather? i think mine does that too

 

[Fmstrat]

Bringing this thread back from the dead...

I too, have a leak at the BISS. I can also hear another leak, but can't locate it. I've sprayed the whole area with soapy water, and no bubbles except near the BISS. So, questions:

1) How do you properly seal the BISS? a rubber cap over it? some gasket maker?

2) What's the other leak? I guess I'll detatch my EVAP stuff to narrow it down. It's very odd though, if I hold my hand over where the TB meets the intake manifold, it changes pitch, yet no bubbles from the soapy water.

 

[95EclipseGST]

Can you order just a BISS and if so, whats the part # ? I have a 1991 throttle body and my BISS leaks very bad also. When i did my boost leak test the pressure wouldnt hold at all but i couldnt find any leaks except BISS.Does the engine have to be in a certain TDC position or anything? I did the test 2 times and cant figure out what im doing wrong.I used soapy water also.My friend asked...doesnt the air just go through the valves and out the exhaust? I dunno im new to this also. Thanks

 

[fixmy97gst]

Can you order just a BISS and if so, whats the part # ? I have a 1991 throttle body and my BISS leaks very bad also. When i did my boost leak test the pressure wouldnt hold at all but i couldnt find any leaks except BISS.Does the engine have to be in a certain TDC position or anything? I did the test 2 times and cant figure out what im doing wrong.I used soapy water also.My friend asked...doesnt the air just go through the valves and out the exhaust? I dunno im new to this also. Thanks

Hey I have an 97gst and I might have a clue for you, I found air leaking around the throttle body gaskets and around the bolts that attach the two pieces together , bad casting from the manufacture because the throttle body has casting irregularities on it...I took some form a gasket and put it on both sides of the metal TB gaskets and now I have no leak...also when you have th TB apart clean it with some carb cleaner and clean all the ports ,even if you have to take the BISS screw out...It can get dirt lodged in there,hence the air leak.... hope this helps

 

[Fmstrat]

Found these that might help:

http://www.machv.com/throtbodseal.html

http://www.machv.com/newbasidsets.html