1999 Deville Sutton Heating Problem Plz help
 

I've got a 99 deville car had 90k on it well kept ederly owned 2ND owner when I bought it...i've had zero problems for the past months up until today I ran a couple errands and the car rode and drove fine for an hour ride.....so I went in store for 5 minutes came back out started car it choked a little at crank but started and made it out of store parking lot I got to a red light and suddenly seen smoke coming from passenger side of car near the battery i got the car home in the driveway and checked it out I had a coolant drip trail from the front to back of my driveway popped the hood and the coolant was bubbling I had my mechanic come take a look at it he looked at the heads,hoses, and he even check the coolant tank he removed the top with a rag and I could hear the pressure release but it was still bubbling the temp risen to 255 and the car started to idle rough and the info Center said check oil level,change engine oil, and stop engine it displayed these 3 messages i turned it off and on and he added water to the coolant tank the temp went back down to 223 he said he seen a drip or look of a leak was from the radiator top cap.......help would be gladly appreciated money is tight 😩

Most likely blown head gasket(s). You should have your mechanic do a CO test on cooling system to verify it. Check oil level - engine has a low oil level sensor. It should turn on message when oil is about 2 quarts low. Change oil - probably related to overheating, oil life will rapidly go towards 0 when engine overheats.

Blown head gaskets are expensive. Although I have had not luck with it, there are the "head gasket in a can" products out there. Some are not compatible with antifreeze so you know.