Reddit reviews Motorcraft RS-527 Radiator Pressure Cap

you might want a new cap. Ford changed the reservoir cap spring design because the old one would drop from 16psi to usually in a lot of cases 13psi and that lower pressure caused big problems for some folks. New caps are normal for maintenance and I bought this one recently to replace my 14 year old one:http://www.amazon.com/Motorcraft-RS-527-Radiator-Pressure-Cap/dp/B0034RKNPS?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00