coolant pressure release

[92EcoDiesel Jetta]

Is it in the screw on expansion cap and how does it work? There's an o-ring on the inside and I can push on it and feel a slight movement. Is that the valve I'm pushing on? But where does the pressure go? I don't see a hole any where on the cap and when threaed in it appears to be totally sealed!

[myke_w]

Yes that's it.

It goes out through the valve to the edge of the cap, drains down in the channel that surrounds the thread and exits on the under side of the bottle.