Re: Question for those with vacuum gauges

[SailingFC@aol.com]

In a message dated 97-06-06 01:41:31 EDT, eg1@ee.wustl.edu (Ilias Glavinas)
writes:

<< I just installed my vacuum gauge and am experiencing some funny behavior. 
 First of all, when the car is idling, the needle fluctuates by +/-2 in, 
 and as a result makes an irritating sound. I don't suppose that is normal 
 now, is it? Somebody told me it could be a sign of a valve not closing 
 well. 
 
 Secondly, when I am accelerating the needle does respond, but again it 
 fluctuates while it rises/falls (again making the sound).
 
 I 'd like to hear about the behavior of other listmembers' vacuum gauges 
 (mine is a VDO, and I set it up the usual way, tapping off the 
 usually-covered outlet just before the hose that goes to the booster). 
 
 Could it be a defective gauge? (I hope so :-) >>

-------------------
The fluctuation is not normal.  I use a VDO vacuum gauge on my '78 w/'84 1.8L
motor.  I have it tapped at the same place as you.  I get a very steady 20
in. reading at warm/hot idle.  I've never had to actually diagnose a problem
with my guage since it's been installed, "knock knock"(on wood).  From what
I've read about diagnostics with a vacuum gauge,  you may have a burnt valve,
a valve that is out of adjustment(solid lifter) or a bad hydraulic lifter on
one of the cylinders.  What is the number when you are warm idling?  It
should be between 18 and 22 in.(with maybe a half point variation).  If you
are not at sea level, your reading will be one inch lower for every thousand
feet of elevation.  Example - 20 in. at sea level, 19 in. at 1000 ft above
sea level, 18 in. at 2000 ft above sea level, etc.  This assumes there is
good compression in all the cylinders and the pressures variations between
cylinders are within acceptable limits.

Good luck.
-dick-
'78 Scirocco
Original owner.
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