[s-cars] Pressure Test

[Steve Eiche]

Mike,
I successfully used this technique last week.  The car in question was a
95.5 S6.  We installed the adapter at the MAF hose, plugged the PCV
(important to do, or you will pressurize the crankcase, which can end up
blowing oil past the turbo seals creating quite a smokescreen on
start-up) and attempted to pressurize the system.  It was immediately
apparent that the there was a leak in the turbo to crossover pipe.

A quick band-aid repair was done with duct tape (it held 24 PSIG until
the Samco hoses arrived BTW) and the system repressurized with 10-15
PSI.  This time it held pressure.  At least until the adapter blew off
the MAF hose and scared the sh*t out of me with my head being right next
to it at the time.   You would be surprised at how pressure tight the
system is, or at least should be.

Steve Eiche





Ed -

? "An adapter...."  Singular?

I may be missing something here, but what, if anything, do you do to keep
air from leaking past the throttle body or ISV, into the intake manifold and
from there, I presume, out one or more of the five cylinders with an open
valve or two? Or worse, into a cylinder that may have its exhaust valves
closed, and past the rings?  There may be some things you really don't want
to find out about, yet....  :-).

Do you hear, see or feel any air coming out the tailpipe or up through the
crankcase?  Or, are we doing this thinking the throttle body butterfly plate
& ISV valve are pretty air tight?  The ISV hose may be small enough that you
can "pinch" it off with a pair of long nose vice grips, but the throttle
body hose....?  I think you need to pull it off the intake manifold & plug
it off as well.

My guess is, if you have a hole or a crack, 3.5 psi is the threshold
pressure required to hold it open enough to cause the leak to be noticeable.

I think maybe you need an air compressor mit tank and a pressure regulator
which can  be set to put in and then (try) to "hold" pressure at a 15+ psi
level while you look for the source of the hissing sounds.  Sealing off the
intake should take your ECU pressure sensor out of harms way as well.

Mikey