Immediate shut down will prevent the engine temp for reaching warping temp
for the heads or release points for valve seats.  Short quick runs on a cold
engine should have minimal effect.

However a hot engine that has been running up to temp and then looses its
coolant only has a minute or two before it reaches those temps on the heads.
It will probably take slightly longer for the pistons and then the bearings
to hit destructive temps.  As for your temp gauge/light senders.  They are
useless if there is no coolant in the system. you would need a head temp
sensor and gauge like used on many aircooled to track head temps which is a
critical temperature.

Jimt

On 5/23/05 10:02 AM, "Aaron Pearson" <Aaron.Pearson@GXT.COM> wrote:

> why does coolant loss cause engine damage?  i had catastrophic pipe
> failure, but stopped before the engine temp went up.  i knew my pipe was
> close to failure, and stopped as soon as the light started to blink.  i
> had to run the engine a few times before the coolant went back in (to
> manuever it to the tow truck, and to get it in the garage), but the temp
> gauge never went above normal.
>
> aaron
> '87 syncro gl
>