Are you running both factory fans ? Only running one can be causing a higher temp which causes higher pressure causing seepage. What temps are you hitting ?
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this cap issue seems to be happening to me as well. When I'm driving the hood starts to smoke white for a few seconds and then stop. No overheating. It smells burnt real bad. Definitely coolant burning off on a hot surface. When I pop the hood I don't see anything wrong. No coolant on the ground when parked either. It's gotta be coming out of the cap.

 

Steam ....

 

R u replacing the coolant that has escaped as steam????

 

Yes. It's a small amount though.

 

Think about it, if the cooling system is not holding pressure, coolant will boil at 212F.....not good.

 

Seen it many times .

 

I had over heating problems, mainly when crawling. I went to a open system, 16 lb radiator cap, a wj fan clutch and auxiliary fan, and a flowkooler water pump. Hood vents are a must ton of heat get trapped in the engine bay. I also disconnected my tranny from the radiator and it now only goes to a b&m plate cooler with fan. Made all the difference in the world.