The automatic transmission has a remarkable habit:
when driving on a daily basis it is fine, but after not using the car for 2 weeks or more, ATF oil drips out of the tranny, making a puddle underneath. Sometimes it is a big pool, like 1 liter of ATF wasted on the floor. "Marking the territory"
This phenomena is caused by the torque converter, ATF cooler, and ATF lines empty themselves, seep through the one-way valve and gradually increase the fluid level in the transmission. It actually goes way over the level of the seal, filling the tranny over its maximum. When this happens, two things become critical:
1. the seal of the transmission pan should be tight. Not over tightened, but at the correct torque, holding the ATF inside the pan. If the pan is not flat, the seal is old, or the pan is too loose, ATF seeps out of the pan. The seal becomes less elastic over time and needs replacing. Torque at only 8Nm which seems like hand tight.
2. the red cap on top of the reservoir should be really tight. The rubber O-ring should be in good quality and the cap should be pressing firmly to avoid ATF dripping out. This is actually the reason why there is a hex-nut molded on top of the cap. Too tighten it firmly and loosen it later. The O-ring tends to become hard during time and sometimes needs replacing.
Just to add the required torques for tightening:
Pan gasket bolt torque: 8 Nm = 5.9 ftlb.
Drain plug - pan: 14 Nm = 10.2 ftlb.
Drain plug - converter: 14Nm = 10.2 ftlb.