Baby, it's cold inside!

[chris.miller at infofoundry.com (Miller, Chris)]

> Jim,
> 
> It may work good now, and it may continue to work well, but those
> little $10 vacuum pumps do not completely evacuate the system, leaving
> traces of water vapor.  That combines with the 134a and turns into a
> vicious acid (hydrocloric IIRC), and starts eating aluminum inside the
> system.  What can happen is it will work great now but in a year or
two
> the system will look like swiss cheese.
> 
> Been there, done that.


Whatever kind of pump you use, try to do it with the system as hot as
possible.  

At 69 degrees F, the boiling point of water is a vacuum reading of 29.22
in Hg.   Raise the temp to 104 degrees F, and you only need to suck the
system down to 27.75 in. Hg.  Doesn't sound like much of a difference,
but it is, especially with the cheaper pumps.

So, hot sunny day with the engine compartment open, or run the engine a
while and let everything get nice and hot.

Chris