Radiator overflow

I didn't think u had a catch can. If you put one in, you will find a lot of your problems with this particular issue will disappear. I didn't have one either and I had a simialar problem, put a catch can in and problem gone. I used a catch bottle from a 73 Satelite and used my hot rodding inginuity to make a spot for it where the old carbon cannister used to go. You can kinda see it in this pic, it allows your coolant to expand and contract and yet keep the cooling system as full as possible at all times for best cooling capabilities. It is a worthwhile investment in time and effort. Cost for me was $0