On Tue, 19 May 2009 20:05:29 +0200, "Edgar"
wrote:

Even without leakage if you drain and refill every winter the build-up will
continue until it poses a problem, so it is better to winterise with
antifreeze rather than draining every year

A long time ago cheap antifreeze was methanol, and you put it in in
the fall and drained it and replaced it with water in the spring. You
had a 140 degree thermostat for winter and a 180 degree one for
summer. That went out more than fifty years ago. Now you use a glycol
blend and replace it every two years. 220 degree thermostats are
common. The system is under pressure, which raises the boiling point.
You are in deep ship warpage wise if you get a modern engine hot
enough to boil the coolant. The boiling begins in the cylinder head.
When it warps you blow the head gasket. If it warp is permanent, you
have to remachine it flat, or a new gasket will not last. Cadillac
built an engine that would run, at drastically reduced power, without
coolant. The cylinders fired half the time, the other half air
cooling. Gets you out of the desert even if you blow a hose. Everyone
else replaces dubious hoses before they head for Vegas. Cadillac had
trouble with boiling brake fluid. When they discovered it was driving
around with a foot on the brake pedal that caused the problem, they
specified a higher boiling point fluid. They knew you couldn't educate
the geezers.

Casady