Try pressure testing again and listen for the leak if you can't see it.I just pressure tested mine and heard a leak behind the drivers wheel well so it's probably the plumbing behind there or maybe the overflow container itself. From what I've seen normal coolant temp when all sealed up and working is under 200. I can't get mine under 200 and for sure have a leak.

 

my Coolant is a rock steady 194, oil varies from 210 to as high as 221 (hot day, sustained speed)

 

I think around 200 you have small leak over 210 you have a big leak. 194 is when everything is all sealed up and working good. Oil I can get down under 210 if I turn on sport. I think it turns on a oil cooler.

 

mine will actually drop down to 195 if I put it in sport or sport+

 

Huh,

Yup, pressure is not holding, in particular I noticed it start to drop around the pressure where I can see the bleed valve plunger rise up due to pressure. There's a little wet spot behind the connection tube from the bleed valve to the expansion tank/reservoir. I wonder if I could get away with replacing the tube only or need to also replace the reservoir?...

Thank you both I didn't know a leak can be seen in temp like that!

 

This is the tube as connected to the bleed valve. Looks like a leak at the other end as there is a small wet spot in the vicinity.

 

I can hear my expansion tank leaking but can't see it. I think mine is coming from the top. Part is only 100 can't hurt to try. It doesn't seem like common part to fail. But it does explain why we lose a bit of coolant then it a stops. The leak must be up high and would make sense if it's the expansion tank. I'm almost positive you have same issue. If you can pressurize it up and listen behind the drivers wheel well you should hear hissing.

That part you have pictured the other end goes to the tank in the wheel well.