The manual refers to this blinking light as being caused by the expansion
tank. A sort of spherical container just before the holding reservoir.

Pouring water directly into this will suppress the blinking light however
I think it a symptom of a more serious problem.

>I'm a new owner of an 87 Vanagon GL.  For the past couple of days the
>coolant blinker light occasionally blinks for a few seconds and the car
>often "hiccups" at the same time.  The temperature needle seems fine,
>always right in the middle (well, just below light) at operating temp.
>Coolant level seems fine, V-belt seems fine, I don't know about the fan.
>What else?
>
>Jerome