On Sun, 21 Apr 2013 23:31:02 -0700 (PDT), harry
> wrote:

>On Apr 21, 11:21*pm, Ashton Crusher > wrote:
>> 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.

Harry, you are incorrect on this. The cap alone WILL cause most
suystems to run at a higher pressure as long as the vehicle runs at a
minimum of 160F. The thermostat only controls the MINIMUM operating
temperature of an engine, so even an engine with a 160 thermostat can
run at 195F, or higher. The cap allows the pressure to build to a
MAXIMUM of the rated pressure - at which point it releases into the
overflow to regulate the pressure.
>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.
>
>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.

Or bad timing, or bad mixture, or simply overloading the engine. But
yes, you got ONE thing right - installing a cap with a pressure higher
than the system is designed for CAN cause problems with hoses,
radiators, heater cores, etc..