Three problems related to coolant leaking have been reported for the 1996 Cadillac Seville. The most recently reported issues are listed below.
The contact owns a 1996 Cadillac Seville sts. The contact was driving approximately 25 mph and smelled a strong burning odor of fumes inside of the vehicle. The engine began to overheat, causing the temperature gauge to increase rapidly to hot. The contact maneuvered to the side of the road to inspect the vehicle and noticed a substantial amount of coolant leakage underneath the dashboard and the front passenger floor area. The vehicle was towed to the residence. The vehicle had not been diagnosed or repaired. The manufacturer was not made aware of the failure. The approximate failure mileage was 138,000.
Northstar engine problem - the head bolts pulled loose causing engine coolant to leak into the exhaust. Had inserts put in by local mechanic who had previously done two such repairs (Cadillac advised that it only had a 60% chance of fixing the problem if they did the work and the cost would be $3,000 - $4,000). Car had about 70,000 miles on it at time of failure. Car ran well until October 2008 when coolant loss started again. Have tried various sealant but it is likely the head bolts again. An aluminum block with aluminum heads and high compression appears to be combine with a weak design of the head bolts. From what I hear all northstar's of this era will have this problem at some point and the problem was not fixed until 2001 or so. It is said that a jeg's motor has addressed this problem but at a cost of what, $3,000 plus installation? I like the car but it is hard to work on and has its share of issues.
Gm has a known problem with the cadallic northstar 4. 6l head gaskets. They broke down between 70,000 and 140,000 miles gm will not assist in the repair of the head gaskets. Our Cadillac is a 1996 with 72,000 miles and has had the leaking since 40,000 miles. The dealer was and is willing to repair for approx. $3500. 00. We have never been told about the lawsuit that was files and the dealer has known about the dex coolant problem. The dealer will not guarantee the head gasket they said was needed . I did not know that there were service bullittins on putting inserts in the block for the head bolts. I think over 50% of these engines have had the gasket replaced. This was a problem, but I know that they like the money that it brings in to them.