> I have replaced my pressure cap several times with a Stant 16 PSI cap.  It
seems to hold 16 psi when new
> but in very little time (10 - 20 hours of use?) the holding pressure is
down
> to around 10 psi where it stays.  Anyone else see this?  I'm going to
order a
> 20 psi cap from CR Racing & see if it does any better.
>
>  Tracy
>
> Tracy, I have been using a 24 psi CR Racing cap for over 100 hours, it
> quickly settled down to releasing at 21 psi (based on my coolant pressure
> gauge reading) and has remained at that to the current time.
>
> Ed Anderson

As I have followed this thread, I have been having vapor problems also!  (Is
this a case of aero-hypochondria?)

Since I have installed the thermostat, I now am getting vapor blown out of
the overflow tube from the cap to the holding tank.  I have tried every
different way to make sure there is no air in the system to start with, but
after flight there is always air in the tube.  As the engine cools, it pulls
fluid back into the system, but not before it also pulls in the air from the
tube.

This was never a problem in the thermostat-less prior system.  What's going
on?

My cap is a stock Mazda which I believe is about 16 psi, but my pressure
guage runs around 20 psi.  The cap is new as is the part it screws into.
Looks like more gremlins to exorcise.

Bill Eslick