"David L. Martel" wrote in message
...
Ashton,


No, the car is not overheating. It's never overheated. What happened
is that I installed an AC unit in this 60 Dodge. That has made it run
about 10 degrees hotter then it used to, mainly from just having the
condenser there in front of the radiator. So I was thinking about
whether it would be a good idea to go to a 13 pound cap instead of the
7 pound one on it.

I don't follow this. Your radiator is running about 10 deg. F (?) hotter
with the AC, so what? Why is that a problem? You aren't anywhere near the
boiling point of your coolant, are you? Assuming you have a 50:50 mixture
and 7 psi your boiling point is about 255 deg. Changing to a 13 psi cap
would improve things by raising the boiling point to about 270 deg.
Unless you are getting close to 250 I don't understand why you want to
do this. Be sure to check my math. These figures are quick guesstimates.
Sorry, sounds like a waste of money. Keep an eye on the temp gauge this
Summer though till you're sure.

Dave M.

There is noting wrong with your logic. The coolant is already being ported
into the overflow tank with the OEM pressure cap. Putting in a cap that
cracks at a higher pressure probably won't even change anything with respect
to when the coolant starts to go into the overflow tank. In a closed system
(completely full and cap shut) the coolant pressure increases rapidly as the
fluid starts expanding (without the cap opening the pressure could easily
get up to a 1000 psi). Going from 7 to 15 psi would have a relatively
insignificant change in the way things work. It doesn't change the
operating temperature, just raises the boiling point of the coolant. And
operating at a higher pressure than OEM is moving in a trouble direction.
BTW, one can calculate pressure vs temperature in a closed system--just look
up "Bulk Modulus" and fluid compressibility.
MLD