[s-cars] Chasing a boost leak

[Tom Green]

The valve cover should be under a slight vacuum, Mike, courtesy of the
emissions system plumbing under the intake manifold that removes the
products of piston blow-by and valve seal leaks and re-routes them
back to the intake.  That hose actually runs through the valve cover  
from
the crankcase, and the oil and fumes get sucked right into the  
turbocharger
compressor and right back to the intake, except for the oil that  
collects in the
MM hose and intercooler.

If your system can't hold a vacuum, it may not operate the wastegate  
or the
BPV properly to obtain full boost.  The WGFV and BPV require vacuum to
operate properly, so just the electrical solenoid clicking is not  
good enough.

A new oil cap gasket certainly can't hurt, but it still won't hold  
boost.  :-)  If your
valve cover did get pressurized to 22psi with the engine running, I  
would
expect the oil seals (and cap) to whistle an angry tune.  You should  
feel a
slight resistance from the vacuum when removing the cap at idle and a
slight stumble in engine rpm.

Tom

    -----Original message-----
> Date: Sun, 15 Apr 2007 19:36:52 -0400
> From: "Mike Claire" <mike.claire at gmail.com>
> Subject: Re: [s-cars] Chasing a boost leak -
> To: " Vincent Fr?geac " <s.sikss at gmail.com>
> Cc: S-car list <s-car-list at audifans.com>
> Message-ID:
> 	<d219f42d0704151636t5f7b4ed5qbe6ffd32ac4fd473 at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> I hope you're right, I'd be catching a break if just changing the  
> oil cap
> would fix it.  Does the valve cover actually build pressure to 22  
> lbs (in my
> case, with a 1+ chip)?  I thought pressure would just leave via the  
> rubber
> hose that connects to the intake bellows, on the engine side of the  
> MAF.
> That wouldn't hold pressure, it goes straight back to the air filter.
>
>
>
> Mike
>
> On 4/15/07, Vincent Fr?geac <s.sikss at gmail.com> wrote:
>>
>> Mike,
>>
>> I think you found the culprit: valve cover oil cap. Mine was the
>> crankshaft
>> breather hose rubber elbow at the back of valve cover, or should I  
>> say the
>> first leak was... Now it's leaking at the spark plug #3 valve cover
>> gasket... until I repair it and boost find another place to leak.
>>
>>
>>
>> Vincent