boost leak finally found

[dobbin]

finally found a boost leak ! after months of trying to find out why my rs2 wound not boost over 1.55 max and hold strong there ,( should be around 1.8 to 1.9 bar).
after changing every small hose off the manifold which i did have small leaks ,
today i spent over 2 hours spraying down every hose again and throttle body to find at 1.6 bar plus the isv valve was leaking from the back of the housing where the plastic housing fits to the outer casting (plug block).
now can i strip it down and seal it up or just fit a new one ?
by the way i could not hear any air leak at all up to 2 bar pressure only by spraying it
with soapy water did it show.

[UrS4boy]

N71 Idle Speed Stabilization Valve (ISV or ISS Valve) Info

Must be an internal leak past the ISV valve shaft seal. Doubt that you can fix it properly.

Here is some ISV info, including Bosch PN:

http://forums.quattroworld.com/s4s6/msgs/21853.phtml

[s2driveruk]

good find, not seen that as a culprit before but one to add to the list of possibles now

[madpugger]

It always really confuses me how such a small leak can affect boost so badly, I mean if you look at the volume of air it takes to produce 1.9 Bar, how can a 'drop in the ocean' cause such grief?!

[s2driveruk]

yup....i had one in my IM casting and caused loads of grief!

[QuattroFever]

What IM oem?

[dkw_dude]

Had the same experience a few years ago, when pressure tested and sprayed with soap water the IAC produced bubbles @~1,5 Bar or so (from memory). Bought a new one, installed and pressure tested again and still bubbles. Maybe a little less, but still bubbles.

[prj]

ISV's on all of these cars leak.
Epoxy the back.

[macspring]

Prj,

Any photos of what you did with one of yours ?

Thanks.

[ChrisAudi80]

ISV's on all of these cars leak.
Epoxy the back.

Had the same thing recently. The idle was crap, too. Epoxied the back of the ISV.
Fixed.