Would it help to remove radiator cap when vehicle is sitting in severe cold ??
To allow for expansion if there is freezing of fluid.

 

No, wont do much of anything. If your running regular antifreeze and are concerned about it, a 70% a/f to 30% water will give you protection to about -80 degrees. If your still worried you can also run a block heater that taps into your heater hoses.

 

If your coolant freezes, you're screwed, cap open or not. As said above, run a regular mix of 50/50 (Toyota Coolant), and you'll be fine in WI.

 

When I first read your post, I thought you might be stationed at the Russian Vostok station in Antartica or something.

On a nice balmy Wisconsin winter day, you'll be fine with a 50:50 mix of Toyota coolant and water, which will not freeze until temps get down to approx -35 deg F. You are not likely to ever see temperatures that low, since Milwaukee's lowest ever officially recorded temperature was -26 deg F.

Like others have mentioned, leaving your rad cap off will not keep your block from cracking, because water expands in every direction... not just towards the path of least resistance.