2001 PT Cruiser regurgitates p/s fluid on start-up in cold weather. Pump has been replaced. Steering "whines" when turning as fluid becomes low, filled reservoir, fluid

burped back up through reservoir when in cold weather. Does not do this in warm weather, or when vehicle has run enough to warm engine. Has been to dealer, and several mechanics, no fix/answer. Present mechanic suggests possible replacement of rack, as that may where system is drawing air on start-up. Sound familiar to anyone? Thanks.