Gentlemen, my nice mild mannered 69 Malibu convertible is once again displaying a nasty habit from which I thought she had recovered. The coolant that is supposed to live in the rad and engine has a way of running out of the overflow tube and onto whatever roadway or driveway we are on. Then the idiot light comes on. This is double trouble because now the same overheating problem rears its head and there is less ( or no ) coolant in the rad. When I top it up it takes plenty. I am aware of the usual suspects rad cap, rad, rad cores pinched off, water pump, thermostat, fan shroud or lack thereof. Just wondering where to start. Also, why would it drain the rad ( no leaks...it comes out the overflow ). Should this model have a fan shroud? Should it have a coolant recovery tank. Thanks for any insights and wisdom. R.B.

My first suspect would be the radiator cap. Once it relieves the pressure, the water in the cooling system boils out like a geyser, then you're screwed. You should have a coolant recovery tank to keep the excess cycling back into the engine when it cools off.