996 need headgaskets ?

[gearjam]

I have a 1999 996 that I keep loosing coolant. I have pressure tested it and never see a leak anywhere. When I start it in the morning it seems to mis a bit then it's ok. I never see smoke when starting it though. If I start it in the morning and go and unscrew the cap I hear pressure being released. Think I need headgaskets?

[Plavan]

Check coolant tank. Hairline cracks can still hold pressure to a point then it spits it out. I had to replace my tank with only 40k miles when I had my 996.
Is coolant leaking from the driver side rear?
Look under the engine and look for white color stains near the exhaust headers.. Looks like dried saltwater