In Canada, most people run with the same 50/50 mix all year round in all
vehicles. No one would take the chance of freezing up and possibly cracking
the block in mid winter. Summer temperatures can range from the low 70's to
mid 90's (Deg F) depending on where you live. The worst overheating
condition here in Calgary usually occurs when stuck in traffic. Larry.
-----Original Message-----
From: John F Sandhoff [mailto:sandhoff@csus.edu]
Sent: Friday, June 08, 2001 11:56 AM
To: datsun-roadsters@autox.team.net
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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