Re: Phil, you're on to something-urq positive crank ventilation

[GaidosIII@aol.com]

Thanks Phil,
 One of the questions Ron asked me is what are the emmission control
differences between your English quattro and the ones here in the states?
Would these differences effect the crankcase ventilation setup?
 The thing I noticed is the car did not completely die when I opended the oil
filler cap. Of course I only cracked it open a little that probably had
something to do with it.
 I guess the good news with this is there isn't any sign of foaming oil, at
least not yet and in all likelyhood this problem shouldn't be a show stopper
for the time being. That is good because it means I can wait until I get home,
do it myself and save some money in exchange for some frustration.
Thanks Phil and all others helping educate me
Anton

In a message dated 98-07-15 04:06:12 EDT, quk@isham-research.demon.co.uk
writes:

<< I think the ur-quattro is _supposed_ to have crankcase vacuum.  There
 are certainly no restrictors in the breathers.  On the MB engine, those
 breathers are even wider - mostly 1" or more internal diameter, and
 that turbo can _SUCK_.
 
 The "stumble trick" works because the engine is trying to suck air
 through the air filter and up past the metering head paddle - the
 so-called 'air mass sensor'.  The breathers come into the system _above_
 this - so if you suddenly supply airflow into the breather system, less
 air passes the paddle and the fuel is partly cut.  On a properly set
 up MB, the engine stumbles and almost cuts when the dipstick is pulled
 out, and dies instantly if the oil cap is removed.
 
 HOWEVER - this is only true for engines that have good cam and crank
 seals, and have been set up as Audi lays down - with all the breathers
 _DISCONNECTED_ and plugged.  Do it this way, then reattach the
 breathers.  If the engine performs differently, you have a leak in the
 engine.  The VAST majority of people who set up an ur-quattro engine
 don't disconnect and plug the breathers - over time, they gradually
 'correct' for the increased air leaks in the engine every time they set
 the CO.  It isn't a true correction, though - it actually moves the
 enrichment curve slightly and leads to a top-end performance fall-off.
 
 There's good news in all this.  Positive crankcase pressure, when
 there's too much of it, foams the oil in the breathers and blocks them.
 Plus (IMO) it's usually a sign of worn rings.  I had a car here a few
 months back where I plugged the air mass sensor breather port and
 held my thumb over the breather pipe from the engine - there was a
 very marked gas pulse once per revolution.  #3 was also at 1/2 rated
 compression - go figure.  A sustained crankcase vacuum at least
 implies good rings.
 
 I think you still have a problem - the crankshaft rear seal - that is
 just as expensive to fix as a clutch bearing.
 
 And, as an aside - since I ran the Passat for 2 x 1/4 hour oil flushes,
 compression has improved.  I've forgotten who it was that said "black
 sludge" in oil could gum up the piston rings - but you seem to be
 right.
 
 --
  Phil Payne
  Phone: 0385 302803   Fax: 01536 723021
  (The contents of this post will _NOT_ appear in the UK Newsletter.)
  >>