Coolant condesation and hissing sound

[Joji]

Alright I posted before about my headache with the porsche dealer. They charged me all this money for a cap & pressurizing the system. Mean while I brought it back to them 4 times. now they told me to go away. And th coolant light was still blinking and the car ran pretty high above 180 on the meter.

I called my old mechanic. He said it probably is low on coolant.
I filled it up and the coolant light went away.

After i drive I still hear a sound like air is escaping from the coolant cap and the top of the trunk is misty wet. not dripping but a fine layer. When the car is hot after a drive there is mist coming out from under the cap.
The dealer claims they changed the cap twice because of 2 faulty caps

1. Is this normal for the hissing sound. there is no coolant on the right rear floor. there is no puddle in the trunk and there is no coolant in the resvoir.

2. Also I noticed that when the car was driven that the coolant level has a inch of whitish looking bubbles and then after a couple of minutes as it cools the coolant is back to normal pink color. Is this normal

3. when do you measure the coolant level. after the car sits over night or after you just drove it. also do you check it with the bleeder paper clip thing up or down


thanks