sometimes if you are really desperate,
you can drive with the heater on to
dissapte heat from the engine...yikes!
this only happens when it is hot outside
usually, the time when you would least
want to turn on the heat.
but it can keep the engine from boiling
over .
Also the water pump might be siezed up.
most anti-freeze contains water pump
lubricant to help things to keep flowing
smooth. hope you find out how to fix this
as it is getting hotter every day.
(in the northern hemisphere)