Re: Annoying Engine Tapping

[allanm@PrimeNet.Com]

//--- forwarded letter -------------------------------------------------------
> From: "Jeremy R King" <kingjer@eng.auburn.edu>
> Subject: Annoying Engine Tapping
> 
> About two years ago B.J. at "The Volkswagon Dr." told me that the 
> annoying engine tapping noise in my GL5 was probably lifters.  $550 of my 
> dad's money later (10 brand new lifters + labor), the noise persisted.  I 
> took the car back, popped the hood and told B.J. it wasn't the lifters.  
> He said, "Oh yeah, it could be the vaccuum diaphram."  That, indeed, was 
> the culprit.  It's a diaphram (encased in metal) bolted on to the side of 
> the engine.  There's a metal rod that bumps up against one of the cams 
> that pumps the diaphram.  This creates vaccuum pressure for the brake 
> assist and a coupla other things I think.  Does anybody have a clue what 
> I'm talking about?  Is this just a VW thing on the Audi 5cyl?  
> 
> Usually it's fairly quiet as long as the oil level is good and the 
> weather's not too cold.  But now that mornings are colder, it's starting 
> to get louder.  I know it isn't hurting anything, but it's sooo 
> annoying.  Does anyone know how to shut this thing up?
> 
> I've even taken it off and tried to adjust the huge bolt head that the 
> rod bumps up against.  Any ideas?
> 
> Jeremy R. King
> 1986 VW Quantum GL5
> Audi at Heart

  <snip>

The "vaccuum diaphram" is a vac. pump used to provide additional power assist for 
the brakes.  Usually this is provided by the engine vacuum, but Audi uses this pump 
on some normally aspirated cars.  Mine started this lifter sound about 2 years ago, 
and I just removed the rod that runs on the cam.  No more noise.  Oh yes, the 
brakes can get *very* hard to push under some conditions.

I have heard (check the archives) that it is related to clearances in the pump 
losening up over time.  A local mechanic (Vincent Eng.) claims he can fix it for 
about $100(?) by rebuilding the pump.  As I remember, a new pump from $Audi$ is 
$300+ parts only.


--------------------------
Allan Morris
Phoenix, Arizona
allanm@primenet.com
-------1988--90Q----------