Pressure testing the intake system .......Chapter 3

[Derek Pulvino]

Chuck,

Look for some posts I sent in a couple of months ago on the topic.  I don't 
remember what the "subject" said, probably something about oil leak, but 
that's where all the discussion I'm aware of wrt to oil leaks, leak down, 
and compression testing should tie back to.  It shouldn't be too hard to 
find though, as I haven't posted much lately.  So if you do a search for my 
email/name, you should find it within about 20-back.

In a nutshell, the data I picked up seemed to point towards high leak down 
in the block which is causing increased crankcase pressure and thus forcing 
more air/oil out the breather hose to the intake.  The worst offender was 
cylinder-three.  Though I was informed the numbers I got are in the 
"rebuild" range, the car still runs fairly well.  I thought about trying to 
compare the % leak-down to the "good" range given for our cars in the 
Bentley under "compression testing," but nobody really knew if that would 
work.  IE range in the Bentley for good from say 190-130 psi would equate to 
a "good" leak down to 68% (ie 130/190=0.68).  Ah hell, it works for me, and 
I pay the bills so...

Some people I've talked to have talked about the turbos leaking, but not a 
lot of data there either.  The other thing I thought of with the leak down 
test...not sure leaking valve stems and guides would show up in the test 
UNLESS those leaks/loss of tightness also result in the valves not seating 
correctly.  Also, I noted that your consumption is fairly close to what I've 
observed in the past.

In other news (on the consumption) I haven't checked again recently, but for 
some reason ever since I did a t-belt and made sure ALL of the intake 
plumbing was snug, my car runs smoother, and it seems like the consumption 
has gone down.  First makes sense, second...not so much, but I'll confirm 
over time.  At any rate, I've not been a quart down since I did the belt and 
changed the oil...?

hth,

Derek P


Message: 6
Date: Sat, 31 Jul 2004 15:19:50 -0700
From: Chuck Pierce <cpcycle at earthlink.net>
Subject: Re: Pressure testing the intake system  .......Chapter 3
Cc: 200 list <200q20v at www.audifans.com>
Message-ID: <410C1B06.80102 at earthlink.net>
Content-Type: text/plain; charset=us-ascii; format=flowed

Chapter 3

A friend has a smog test/repair shop, so today I took the beast down to
him to see if we find out the problem of not passing the test.
( I could not use him for the testing portion as I had to take the car
to a test only shop.....a california thing)
He pulled out his O2 sensor tester and the O2 sensor was good ( at least
something is going right!)
The car is still running pretty rich as the Hydrocarbons are pretty high
Then he compared the exhaust gases at the sampling port right after the
turbo and the tail pipe there was very little change. So this means that
the cats are toast.
The car uses some oil probably about 1 qt per 800mi..
So I guess it is time to do a leakage test to see where the problem is.
The car doesn't seem to smoke on deceleration ( valve guides) and the
compression was good when I got the car 2 years ago.
Have the turbos been known to leak oil to cause something like this?
Any more wisdom accepted!!!

Thanks for all the input gang.

Chuck Pierce
91 200tq 20v Avant

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