Covering Grill in front of Radiator when Very Cold.

I live in a city that can be bitterly cold in Winter in Alberta.
I see a small number of passenger vehicles and
quite a few trucks that cover their front grills with a type
of cloth when the weather is very cold, minus -15 to minus-35 degrees
in winter. Obviously this must be to prevent the cold air
from being drawn through the radiator by the fan or even
if the fan is not pulling in cold air just the forward movement
of the vehicle drawing in cold air.

These cloth grill covers have a flap or flaps in the center that
you can open and close. I am interested in purchasing one
of these. Can the car overheat if the flap is closed for too long?
At what minus temperature can you keep the flap closed all
the time. At what minus temperature must you make sure that
the flap is open.

Thanks in advance
Denny B

"Denny B" > wrote in message
...
> I live in a city that can be bitterly cold in Winter in Alberta.
> I see a small number of passenger vehicles and
> quite a few trucks that cover their front grills with a type
> of cloth when the weather is very cold, minus -15 to minus-35 degrees
> in winter. Obviously this must be to prevent the cold air
> from being drawn through the radiator by the fan or even
> if the fan is not pulling in cold air just the forward movement
> of the vehicle drawing in cold air.
>
> These cloth grill covers have a flap or flaps in the center that
> you can open and close. I am interested in purchasing one
> of these. Can the car overheat if the flap is closed for too long?
> At what minus temperature can you keep the flap closed all
> the time. At what minus temperature must you make sure that
> the flap is open.
>
> Thanks in advance
> Denny B

If you notice your temp gauge climbing higher than normal, open the flap /
take it off.

Another thing, most cars only turn on the fan when the rad is hot, so it
would actually want cold air in that case.