non triumph - losing water out of rad.

[sujit roy <triumphstag@gmail.com>]

On long journeys in my daily driver, water get pushed out of the rad
and into the overflow bottle.  When the car cools down, shouldn't he
water return to the rad?  If is doesn't can I assume the rad. cap is
the problem.  If not, what could be causing the problem?

Honda Civic '95.

Triumph Stag '71 undergoing steering rack rebuild.

Thanks Sujit