Oily cutoff valve

Phil Rose pjrose at frontiernet.net
Tue Aug 3 17:58:30 EDT 2004

At 5:00 PM -0400 8/3/04, Kneale Brownson wrote:
>I replaced my overrun cutoff valve (popularly known as the wastegate or
>bypass valve)

Not related to wastegate operation--the BPV is also known as 
"throttle body overrun cutout valve"

>  today because I've had the engine dying on deceleration
>experience several times in the last week.  I'd replaced it in the spring
>with a "good" used one I got in a purchase of a boxfull of parts because
>the car was doing the same thing (dying at stoplights) occasionally during
>the winter.

My test for BPV "goodness":

(1) Use Mity Vac on the small nipple to operate the  valve--showing 
it can be opened and will hold a vacuum indefinitely. (2) Test that 
neither of the large nipples will permit flow of air when valve is 
closed (both ports should hold tight under moderate positive and 
negative pressure). This is easily done "orally".

>Anyway, I noticed that the one I took off had oil on it just like the
>inside of the Michelin Man hose gets.  Is that normal?  I didn't remember
>the other one being oily last spring.

The ones I've inspected/rejected have been _somewhat_ oily, but not 
with significant amount of liquid (as compared with the typical 
Michelin Man).

>What fails on these things, anyway?

They usually develop a tear in the thin, flexible plastic bellows 
material (valve). This will cause the valve to fail to open when 
under manifold vacuum. Of course you're  aware of the propensity for 
the small vacuum/pressure hose to become brittle and blow apart), 
which causes an otherwise good valve to be inoperative (and also 
allows boost pressure to leak). I believe that both defects (torn 
valve bellows and the torn hose) can produce the same stalling 
symptom--independently. So best not to replace the valve until the 
hose is verified to be OK.


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

More information about the 200q20v mailing list