I would suggest a new radiator cap they seem to be rather important on deloreans.The exhaust putting presure in the sysytem is unlikely the bubbles come from water boiling inside the engine block where it is still VERY hot even after sitting awhile.On most cars the coolant system is held under a slight pressure to help keep it from boiling,when you open the system and relieve the pressure the water can then boil.Make sure you are using a 50/50 or 60/40 ratio of antifreeze to water. hope this helps a little --------------------------------- Do you Yahoo!? Faith Hill - Exclusive Performances, Videos, & more faith.yahoo.com [Non-text portions of this message have been removed]