On Apr 22, 2:31*am, harry > wrote:
> On Apr 21, 11:21*pm, Ashton Crusher > wrote:
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> > I was thinking of putting a higher pressure cap on one of my cars to
> > increase the factor of safety against boiling. *Looking thru the web
> > for info on the likelihood of changing from 7 psi to 13 psi causing
> > leaks I found little on that issue but did find a couple references to
> > the pressures created by the water pump. *One site boasts of a 19 PSI,
> > $25 cap to get you thru your "hard driving".http://www.mishimoto.com/mishimoto-h...tor-cap-13-bar....
> > Thought I'd see if anyone else has heard of this. *The claim was that
> > the water pump could create over 30 PSI of pressure. *Since that is
> > double the normal operating pressure of most modern cars I find it
> > hard to believe. *If the system was at full 15 psi of pressure while
> > the car is idling and then your floored it and ran it up to near
> > redline * and created another 30psi of additional pump pressure, or
> > even 10 psi of additional pressure downstream at the radiator cap, you
> > would immediately cause the system to have to vent to the overflow to
> > relieve this higher pressure. * I've never seen a car vent due to me
> > revving the engine up while I'm working on it. Thoughts?????
>
> The only way to increase the system pressure would be to change the
> thermostat to a higher temperature one so increasing temperature as
> well as pressure.

Dumb as ever. The current cap releases pressure at 7 PSI when
the car overheats. He's proposing changing it to 13 PSI so that
when it is overheating, it will not release until that higher pressure
is reached. That results in a higher pressure when overheating
exactly as he claimed and doesn't require changing the thermostat.



> You would then have to change the radiator cap too. But changing the
> radiator cap alone wouldn't change the pressure but in the event of
> engine overheat/pressure would negate the protection it gives.
>

Dumb as ever. When the engine overheats, which is what he's
specifically concerned about, having that higher pressure cap will
result in higher pressure.



> Very unwise, you may get hoses bursting and engine overheating .
> If your engine is overheating there is a problem with the radiator
> (blocked) or the thermostat not fully opening.
> Possibly slack belt (drives the water pump).
> Electric fan (or it's thermostat) if it has one faulty.
> Waterways in cylinder block/head blocked/corroded.- Hide quoted text -
>
> - Show quoted text -

That part is correct. Even a stopped clock is occasionally correct.