2001f4s

I'm going to try the blowing into BOV think and see if it leaks.
Is there any advantage of buying a fancy BOV over the standard type, other than appearence?

elargentino

An o2 sensor cannot affect something until it's effect is seen on the sensor. Since we are checking at the intake, the o2 sensor would need a time machine to prevent valid test for rev change.

It is most likely NOT the bypass valve.
A vacuum reading of less than 10 inches of mercury are most likely not coming from a vacuum SIGNAL line - but something larger.

Most likely:

Broken (but still held in place by hose) cycle valve nipple
Folded under IC union
Ripped UNDERSIDE of turbocharger oulet pipe
Leaking manifold gasket
Mis-aligned manifold gasket (you only hit one hole)
Brake booster line cracked
Brake booster valve toast

refresh951

elargentino,

Did you see in the earlier post that if he pinches the vacuum line to the BOV he gains 5-6 inhg?

His aftermarket vacuum gauge is tee'd into the same vacuum line that goes to the BOV, therefore its reading will be more "affected" by a leak at the BOV.

elargentino

Why are you guys calling it a blow-off valve?
There is a huge difference between a bypass valve (factory) and a blow off valve.
A BOV CAN actually cause a laek, because it vents to atmosphere.
A bypass cannot (impossible) because even if the diaphragm is leaking, the air re-routes from one side of turbo to another.
Does he have a bypass or blow-off valve?

A 5-6 inch difference IS possible with a signal line, yes, but he is at 8?
That is too much for JUST a signal line, unless many are open. And I doubt that is the case.

There are a few more common 951 places to check, but the ones I have given are the starters.

refresh951

Scott,

From what I have heard the stock DV has a diaphragm that is prone to fail. I went with a billet style DV from LR.

2001f4s

Shawn and Elargentino,

Thanks again for the help on this.

Thank you for the list of possible issues:

Broken (but still held in place by hose) cycle valve nipple (Not sure where to find this)
Folded under IC union (Not sure where to find this)
Ripped UNDERSIDE of turbocharger oulet pipe (replaced boot)
Leaking manifold gasket (checked and are good)
Mis-aligned manifold gasket (you only hit one hole) (Not this)
Brake booster line cracked (could be, will check)

Can you direct me to a location on this first two please.

Will also be replacing the BOV, as I am convinced this is at least part of my issue.
Brake booster valve toast

elargentino

The cycle valve is under the intake manifold - can be seen by looking between runners 3 and 4 from above. Look VERY closely at the 3 plastic nipples -notorious failure point.

The ic hases at the ic can be folded under, underneath.
Reinstall them and tighten securely.

Scott H

A good choice, no problem.

boerge

Pressure tested with 0.5 PSI today to find leaks, with a smoke tester, and it came up with a leaking throttle body. (Through the shaft assembly, not flanges) This leak I could hear but not find with soapy water, it sounded like it came from underneath the intake. With smoke on, I found the TB to leak, and that with only very low pressure! (Smoke Machine doesn't do higher??)
So rebuild kit is on its way. Just for your info.
By the way, car drives like crap, either because of this or a mix of other leaks.

2001f4s

boerge
Where is your vacuum at warm idle. I also bought a throttle body rebuild kit, but havent installed it yet.
I figured I had a leak at the TB, but did not think it would impact the vacuum that much. I believe my car runs and idles pretty well with about 8inHg. Tomorrow I will install my new BOV and hopefully get it into the 14inHg range.

2001f4s

SUCCESS. Replaced BOV and now I am at about 11-17inHg.
Thanks much to Shawn and Elargentino.
Much appreciated.
Now on to the next project.