Did you replace the whole pump or just the reservoir? Was the replacement new or used junk? Where exactly is it leaking from (cap, return hose)? Was it overfilled? Are you using the correct fluid? How cold are we talking about; barely freezing or below zero?

 

It's not uncommon for the pump seals and hoses to leak in the cold. Once it is determined that the reservoir is not cracked, snug up the fittings and clamps. I would also suggest sucking about 1/2 a cup of fluid out of the reservoir and filling it with a good power steering conditioner like Lucus. Be careful with this stuff in the extreme cold because it gels easily and the result will pop lines and burst coolers. NOT FUN!!!

 

I figured it out. The return nipple has a crack in it. It's a reman. and you can tell its been plastic welded back on. Thanks guys for the reply you were a big help.