Coolant Tank- not stupid, just ignorant about some things

[jb92563]

I have had the overflow on parking issue.
Cause was that I overfilled the coolant level and so out came the extra as I was parking. Problem has never recurred.

The pressure valve next to the fill cap allows the expanding when hot coolant to expand into the coolant reservoir thereby expelling any air that might be in the system.

These expansion pressure valves have been known to leak as the seals get older and the leakage goes down the overflow tube by the right rear tire.
You will see moisture only on the trunk lid above the Cap area if either the Cap or the Pressure valve are leaking, also a crusty residue will form around the pressure valve.

The Coolant Caps have also been redesigned so you want the latest version.

If you don't see any overheating issues and the puddle is by the rear right tire, I would suspect the Pressure valve or the coolant cap.

The coolant cap is very easy to screw down incorrectly and leave a gap so very carefully re-secure it making sure it looks perfectly parallel to the opening.

A coolant tank leak would leak when the tank gets pressurized and forces the crack open and the coolant will end up in your trunk in that scenario.

Just because the engine is warm does not always mean the tank is pressurized as the expansion valve seems to be the gateway to the coolant tank and is not always open.

Hope that helps.