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Re: Pressure cap (was: I'm a dummy...)

To: "John F Sandhoff" <sandhoff@csus.edu>, <datsun-roadsters@autox.team.net>
Subject: Re: Pressure cap (was: I'm a dummy...)
From: "Patrick P. Castronovo" <slick1@mohaveaz.com>
Date: Fri, 8 Jun 2001 14:37:29 -0700
I have access to a new heater core.  What is it worth?


-----Original Message-----
From: John F Sandhoff <sandhoff@csus.edu>
To: datsun-roadsters@autox.team.net <datsun-roadsters@autox.team.net>
Date: Friday, June 08, 2001 11:13 AM
Subject: Pressure cap (was: I'm a dummy...)


>It was written:
>> What then would a 15 LB. cap raise the temp.
>
>The higher the system pressure the higher the boiling point.
>However, the Roadsters (except for MAYBE the '70 model) were designed
>with a 7 pound cap in mind. If you go higher you risk blowing out the
>heater core so DON'T DO IT!!
>
>The pressure cap sets a MAXIMUM. The system will run at UNDER the
>cap rating unless it gets hot enough to try to boil the water, in which
case
>the pressure increases, which increases the boiling point. (This simple
>statement ignores thermal expansion of the coolant).
>
>People that live conservatively have been known to use a 4 pound
>Jaguar cap. Right now I run NO cap and watch the temp gauge and water
>level, since I have a bad heater core (doesn't leak if no pressure).
>NOT the preferred method, but have you tried to find a new heater core
>lately?
>
>BTW:
>Pure water AT SEA LEVEL boils at 212 degrees F. Add antifreeze and
>the boiling point goes UP. Add altitude and the boiling point goes DOWN.
>Add antifreeze and the heat transfer efficiency goes down. Don't add
>antifreeze and you get corrosion, electrolysis, and a leaking water pump.
>I run about 30 percent antifreeze - car runs cooler than a 50 percent mix.
>
>-- John
>     John F Sandhoff   sandhoff@csus.edu   Sacramento, CA

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