RE: 2000 deville coolant issue.
One thing at a time. Report back after you know for sure the surge tank purge line is transferring coolant. Burping a cooling system is different for most cars but general rule of thumb is to get the radiator higher than the engine (jackthe carup) start cold engine with pressure cap off, keep at faster idle 1200, 1500 RPM till coolant drops in holding tank, then while still idling high add coolant andquickly reinstall pressure cap. ( easier with 2 people) Did you add the GM sealant tabs into the lower hose as recommended? Replace the 9 year old pressure cap as well. PUT YEAR AND TYPE OF CAD IN PROFILE SIGNATURE PLEASE!!
2 1984 Eldos, 1991 Allante, 88 Allante (sold)