Re: Turbo Idle screw: To seal or not to seal? That is the question.

[steveb@falcon.kla-tencor.com (Steven Buchholz)]

> > The Haynes manual indicates that idle screw on a 865kt should be sealed.
> > Mine is not and turning it affects idle to a small degree one way or
> > another.  In my attempt to find a vacuum leak it seems that there might be
> > one around this screw. I have to check more closely.  Should this screw be
> > resealed in some way or not?
> 
> ...if you call an O-ring a seal.  The O-ring does the usual thing that Audi
> O-rings do (turns into a hard black plastic-like material) and no longer
> seals or keeps the screw from turning.  Eventually, the screw unscrews itself,
> falls out and you hear a whistling sound from the engine... it may or
> may not be drivable and probably won't start.
> 
> Go to your local auto parts store with the screw and dead O-ring and get
> a little baggie of new o-rings (they always seem to sell them in little
> baggies with 5 times the number you need) of an appropriate size.
> Having given the screw a new o-ring, you'll need to reset the idle.
> You can go thru the measure the current thru the idle stabiliser valve
> method to reset the idle, or you can just set it to the appropriate
> RPM and you'll be fine. I found that if the RPM is right the current
> was right.
> 
> BTW, I put a new o-ring on my idle screw, it was causing a vacuum leak,
> but I don't think it was a significant leak... pre-empting the screw
> falling out was my main concern.
> 
... IME the seal, o-ring, whatever on the OEM screw has an oval shaped 
cross section ... I've never seen the same kind of part available over 
the counter.  You can buy a new screw for ~$6 ... which is probably how 
you'll feel.  I tried Orin's solution myself on the '88, but the replace-
ment O-ring didn't last very long.  If you look at the screw it has a 
couple dozen threads [yes, I know it is really only one ...], so my 
solution was to put a bit of anti-sieze compound on the threads.  This 
has the effect of sealing the threads themselves and adding enough stic-
tion to keep the screw from turning.  I thought about using grease, but 
I didn't want it to gum everything up ...

HTH!
Steve 
Steven.Buchholz@kla-tencor.com
San Jose, CA (USA)