Intermittent crankcase smell in cockpit

I am appreciating what seems to be an intermittent crankcase smell in the cockpit of my 2004 3.4L double cab Tacoma. I've had the truck about 6 mos now. It is Not using oil. It is Not leaking oil. Radiator fluid is new and remains clean over the last 6 mos. No sludge on the valve cover cap. Forum thoughts appreciated.

 

Could be a small seal
leak that is burning off on the exhaust system. They're hard to see and track.

 

I would start looking at the back of the valve covers. The cam plugs are seeping would be my guess

 

Are you sure you aren't smelling tranny oil? Because I can sometimes get a whiff when I roll my windows down and get up on the gears.

 

the HVAC system air intake is outside in the cowl area under the wipers that's where all the fresh air used for the interior Heating/AC comes from.Maybe take to the spray washer and clean out the engine bay and under the trans area see what happens .

 

Are you sure its 'crankcase' smell?
Motor oil, gear oil, tranny fluid, brake fluid, and anti-freeze all have distinctive odors.

 

You could try replacing your PCV valve.

 

Smells.... Could be a plugged vent line to A/C drain. Bacteria growth.
Could be a small hole in the heater core. Probably ok since your is fine.
Leaves or debris that is in your cowl vents?

I'd try a light mix of bleach and water. Pour it into the cowl near the fresh air intake by the windshield wipers.

Next open both doors.
With the windows rolled up, take a garden hose and run water on the outside of your windows. You can gently pry back the rubber seal. You should see water flowing out the bottom of the doors at the drains.

 

How is your hood to cowl seal?