[V8] Cruise control

[Buchholz, Steven]

... remember that any leak in the vacuum circuit will cause this behavior.
In all the Audi cruise controls I've repaired never once have I had to
replace the vacuum motor itself.  My first suspicion would be the switch on
the brake pedal.  I've also had a similar problem that turned out to be a
cracked plastic "T" in the lines.  

No, the CC doesn't work from engine vacuum ... there's a pump and release
valve mounted under the fender behind the hydraulic fluid reservoir.  If the
simple stuff doesn't catch the leak, find the vacuum line that goes across
the left strut tower to the pump and disconnect it.  With the pump
disconnected the system should hold a vacuum ... if it doesn't you know it
is somewhere in the plumbing ... if it does then it is the pump itself.  

Steve B
San Jose, Kaleefohnia (USA)
> 
>    Cruise went out a couple of days ago - First thought - 
> vaccum servo,
> because the peadle moves slightly when I set the cruise then 
> can't seem to
> hold what it's got, if you know what I mean.  Any thoughts?  I haven't
> troubleshot it yet, maby tonight.  What is the common cause 
> of failure,
> the vaccum motor(although I thought it was driven from the 
> engine vaccum,
> but the troubleshooting guide says something about the vaccum 
> motor and 
> vaccum switch), control unit, switch or what?