Help Me Diagnose my Oil Leak???!! 2000 Seville SLS

Place a large cardboard square under the engine area. If 9when) the leak/drip occurs, that will give you an idea of where to start looking. If you can get the car up on a lift, use a good drop light and search. Oil leaks are very obvious.

Do not fill the oil more than halfway up the dipstick hashmark. The engine takes 7.5 quarts of oil, and more than that is overfilled. GM has issued a TSB concerning overfilling and oil consumption. But oil consumption is different from a leak.........

I wonder if your leak is the same as mine. I was told it was a "half case seal"?? And very expensive to fix. Wonder if something just needs to be tightened? My oil pan is often damp with evidence of a very thin layer of oil, but i also keep a close eye on the dip stick, and rarely get the "Check oil level" as long as I am vigilant at checking.

Mine is getting worse and worse. It looks like 95% is coming from the half case seal.

The entire undercarriage is oil coated now.

I have to put a tranny pan under my car cause it leaks so much that is goes all over the place on my epoxy floor.

REALLY annoying that it can leak this much. Id rather have it burn oil than leak.

I can clean stuff up and the next time i drive its all over again, no way to tell where its coming from.......seems to leak from everywhere.

Half case seal can be a real mess. Unfortunately it requires removing the engine to repair. Check for the obvious like the oil pressure sensor or cooling lines to the radiator. Otherwise decide if its worth big $$ to fix. Best price I saw posted here for that job was $1200. Mine was ~$900 but that was after the motor was already out for HGs.

What is the "half case" and what does it look like? Is the seal just a gasket?

The Northstar "block" is in 3 pieces - the cylinder block, cut off at the crankshaft centerline, the "halfcase", which is the lower main bearing carrier and bearing cap bolt girdle, and a heavy cast oil pan. Bolted together they form an extremely rigid structure which is why the Northstar lower end is nearly bulletproof. The halfcase is sealed with a formed silicone "O-ring" gasket plate affair. The reason for the O-ring type seal is that the entire halfcase must seat extremely accurately as it is, in fact, the lower main bearing journal caps. A simple gasket will not allow the bearings to be properly set to clearance.