* Improper gasket installation: This is the most likely culprit. The oil pan gasket needs to be installed perfectly, with the surfaces meticulously clean and free of any debris or old sealant. Even a tiny imperfection can cause a leak. The gasket may not be seated correctly, or it might be damaged during installation.
* Damaged or warped oil pan: The oil pan itself could be damaged (bent or warped) from the engine removal or installation process. A warped pan won't seal properly, even with a new gasket.
* Damaged engine block mating surface: The surface of the engine block where the oil pan sits might be damaged. This is less common but possible if something was dropped or scraped against it during the replacement.
* Incorrect oil pan: It's possible the wrong oil pan was installed. While unlikely, it's worth double-checking.
* Incorrect torque on oil pan bolts: The bolts holding the oil pan may not be tightened to the manufacturer's specifications. Too loose, and it'll leak. Too tight, and you can strip the threads or crack the pan.
* Leak from elsewhere: While you say it's "close to the transmission," the leak might actually be originating from the transmission itself (transmission seal) or another nearby component and running down to look like it's coming from the oil pan.
What to do:
1. Thoroughly clean the area: Use a degreaser and a lot of rags to completely clean the area around the oil pan. This will let you pinpoint the exact source of the leak. Let it dry completely.
2. Re-inspect the gasket and pan: Carefully examine the oil pan gasket for any damage or improper seating. Check the oil pan for any dents, bends, or cracks. Inspect the engine block mating surface for any imperfections.
3. Check the torque on the oil pan bolts: Use a torque wrench to ensure the bolts are tightened to the manufacturer's specifications (found in a repair manual).
4. Consider a new oil pan: If the pan is damaged or suspected to be the problem, replacement is the best course of action.
5. If still leaking: If you've checked everything above and the leak persists, it's time to consult a mechanic. They have the expertise and tools to diagnose the problem accurately. A second pair of eyes can often spot something missed.
Don't continue driving with an oil leak. This can lead to serious engine damage from oil starvation.
