1999 Cadillac STS Engine Replacement

TERRANCEBAKER

MEMBER
1999 CADILLAC STS
V8
FWD
AUTOMATIC
160,000 MILES

I had a used engine put into my 1999 Cadillac STS because the head gaskets were in need of repair. The shop I took it to tried to put a 1998 engine in it but it wasnt the right one. I new I had the Vin9 motor and there arent any interchangable parts for this model Cadillac. When I got my car back, the check coolant and change oil lights were still on. I only get warm air on the drivers side(cold air comes out the passengers side) and my miles display shows my original mileage 160,000, instead of the 90,000 from the used engine put in! My question is, How can I tell if this is still my original engine and not the used one? Im thinking the shop just attempted to fix the gaskets on my old engine!

1 Reply

FACTORYJACK

MECHANIC
4,159 POSTS

First thought, a replacement engine is not going to get you a roll back in miles, that is illegal. You say they tried to put a 98 engine in, did they succeed? It is possible that the oil life wasn't reset for one reason or another(forgot to, or didn't know how). The cold air warm air issue could easily be a dual zone climate control fault. On the alleged repair, who was it that recommended the engine be replaced with a used one, and who was responsible for providing it, you or the shop? It is very probable that the replacement engine has leaking head gaskets as well. If they tried to repair your original engine, there would have been concerns with head bolts that would not torque. It is the head bolt threads in the block that fail over 90% of the time, and the proper repair would involve thread inserts being installed. Identifying the engine may not be easy, it is dependant on how familiar you are with your vehicle under the hood, and how thorough and detail oriented the tech that performed the repairs was. Contrary to parts being interchangeable, there is not that much difference. Valve diameter/lift/duration, and PCM strategy are about all that seperate VIN 9 from VIN Y.