The most likely culprits are:
* Head Gasket Failure: This is a common problem with the 3800 Series II engine, especially as they age. A blown head gasket allows coolant to mix with oil, leading to the symptoms you're experiencing. This is the most serious possibility and requires professional repair.
* Cracked Cylinder Head: Similar to a head gasket failure, a crack in the cylinder head allows coolant to leak into the oil. This usually requires a cylinder head replacement or repair.
* Cracked Engine Block: Less common but possible, a crack in the engine block itself can lead to coolant mixing with oil. This is generally a very expensive repair, often requiring engine replacement.
* Coolant Leak into Oil Passage: A less common cause, but a leak in a passageway between the coolant system and the oil system can lead to similar issues.
What you should NOT do:
* Ignore it: Continuing to drive the car will only worsen the problem and likely cause severe engine damage.
* Just add coolant: Addressing the symptom (low coolant) without finding and fixing the root cause will not solve the problem and could lead to overheating or engine seizure.
What you SHOULD do:
* Stop driving the car immediately. Driving it could cause further damage.
* Have a qualified mechanic inspect the engine. They will need to perform a thorough diagnostic to determine the exact cause of the leak. They might perform a compression test, leak-down test, or a coolant pressure test to pinpoint the problem.
* Prepare for a potentially expensive repair. Head gasket or engine block repairs can be costly.
The fact that the problem appeared suddenly suggests a significant failure, rather than a gradual deterioration. Get it checked out by a mechanic as soon as possible to prevent further damage and potentially save you a lot of money in the long run.
