BPV was: CEL possible O2 sensor 1.6 bar now 1.3 SOLVED?

Phil Rose pjrose at frontiernet.net
Tue Sep 7 20:08:40 EDT 2004

At 6:38 PM -0400 9/7/04, SuffolkD at aol.com wrote:
>Lister(s):  Q below.
>Interesting you mention the dip stick.
>The O ring at the top crumbled when I had it in my hand.
>I need a replacement.  It was the other suggestion by fellow car nut Larry at
>Watkins Glen 2.
>Quite a bit of surprise on the Bosch BPV's leaking (hissssssssssssssssssss)
>at 8 PSI.  The concensus is that the turbo is just working harder to build and
>maintain boost.  Time for another brand?
>Q:  We had a debate on which way the orientation of the BPV should go.  I
>know there is a right and wrong direction. But in testing the valve 
>we found that
>pulling vacuum against it (side port) yielded slightly higher numbers than
>the (presummed) correct orientation when we removed it.
>If we put the pressure on the side (side port) the valve would have pressure
>peeling away a corner of the seal hence leaking sooner than pulling the entire
>seal from below with vacuum pressure.

I'm not clear on how you did the BPV testing:  was the BPV found to 
be "hisssss...ing" while _on_ the car or _off_ the car? When I spoke 
with you at WGI, I assumed it was tested while off the car.

If that's the case, keep in mind that when the BPV is properly 
installed and under boost pressure, there is about an equal amount of 
boost pressure acting _inside_ of the bellows valve as well as on the 
outside of it.  This situation persists until the throttle is closed, 
and manifold vacuum begins to build. But during boost, that positive 
manifold pressure (via the control tubing) helps to keep the valve 
closed. So, if you pressure-test the BPV when it's off the car--by 
applying pressure just to one or another of the large nipples--any 
"leakage" found to occur at fairly low psi may not really be caused 
by a defect inasmuch as you probably are not simultaneously keeping 
an equal pressure inside the bellows (i.e., through the control port 
with the small nipple) as would be the case during normal use.


Phil Rose
Rochester, NY
mailto:pjrose at frontiernet.net

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