2004 Corolla mystery oil leak. 255000 Km / 159000 Miles. It had a slow oil leak getting on to the serpentine belt and spreading it all about. Most concerning is the alternator is oil sprayed by the belt. Changed out the Timing Chain Tensioner oil ring and that did not stop it. Changed out the Valve Cover Gasket and that did not stop it. I spray washed the area for leak ID and it is very hard to detect the source. It is finally dripping onto the garage floor a few drips a day. I plan to remove the crankshaft pulley a replace the crankshaft seal. Should I assume it could be the Timing Chain Cover Gasket and replace that too? I have AllData access, the Haynes manual and BITOG. Not in that order of course. The water pump has to come off to switch out the Timing Chain Gasket, I will replace the water pump if I remove it. January is our coldest month so this is planned for a February mild spell. Any advice is appreciated.