I would leave it until you are ready to start driving again in the spring
and then top it off and see what happens.  It is possible that the leak
only appears in extreme cold and you may not easily find it and you can't
fix it if you do not know where it is.  Once you know what is leaking then
you can perform the appropriate repair. Like yourself I live in a cold
climate and over the years have dealt with leaks that only appear in
subzero( Fahrenheit ) temperatures.  Hoses, gaskets, any joint, seam, or
mating surface, can leak in the cold.

Mark in AK enjoying a +6F heatwave!

On Thu, Jan 23, 2020 at 9:00 AM Alfred Bagdan <abagdan@shaw.ca> wrote:

> We had some very cold weather the past 3 weeks,  -30 to -40 degrees,  and
> there was an antifreeze leak from my 85 Vanagon.  This happens only in very
> cold weather.  The expansion tank is empty but the coolant tank is about
> half full.  I did not check the levels last fall when I parked the van for
> the winter, so I'm not sure where it leaked out.  I can't see anything
> dripping from under the van, but the antifreeze melted the snow and ice
> under it.  The antifreeze is good to -40 deg.
>
> Is it a bad idea to pour in some sealant and run the engine to try and fix
> the leak?  If not what do you recommend?
>
>
>
> Alfred
>
> 85 Vanagon
>
> Edmonton
>