My 1990 240 has a hot oil smell coming from the engine somewhere. I smell it when the car is sitting at a traffic light and the fan is blowing. I also smell it for a while after the car is parked. There is an oil leak from somewhere (never bad enough to fix.) Could the breather box o-rings be bad? (blow test shows lots of air movement through the box to the oil cap.) Could oil be dripping on the exhaust?

If not that where do I look and how?