[s-cars] coolant pressure

[Tom Green]

On Monday December 24, 2012, at 12:20 PM, tonyve <tonyve at shaw.ca>   
wrote:

OK, he really didn't write anything, but I guess he intended to.  :)   
I am guessing that
the subject was Martin's question about a coolant system leak.

> I am hunting down a coolant leak on my 1995 s6 and want to find out up
> to what psi I can put through the system to check. I am thinking it is
> coming around the reservoir from what I can see from residue left.
>
> Martin

Martin, I thought I would answer in this manner since you have no  
others.  You have
this backwards is the problem.  What you want to know is what pressure  
is my cooling
system producing during normal operation, and what should the pressure  
be?  I don't
know if there is a specific answer to the second question, but maybe  
an answer to the
first will be enough.  So, you need to bring your system up to normal  
operating temperature
and, with that, pressure.  But, operate the vehicle in various modes  
with a test cap to
determine the pressure and how much it varies with the load put on the  
system.  Boost is
generally what puts a heat load on this engine.

Now, question two.  The expansion tank cap has a pressure relief valve  
that should open
at 17-22 psi, so nominal pressure should be 15 psi, but will increase  
with temperature as
a result of engine load and ambient temperature.  Prolonged operation  
under boost such
as climbing a long grade on a hot day with a/c operating can cause the  
relief valve to open
when all equipment is operating properly.

Now, if the system will not hold pressure, you can pressurize the  
system to 15 psi when
trying to find the leak.

HTH

Tom '95 S6
          '95.5 S6 avant
Knoxville, TN