Visual Test Method
WARNING: This page is about a different car, the 2010 Dodge Charger and 2010 Chrysler 300. However, it is still accessible from the selected car via links, so may be relevant.
With the engine cool, remove the coolant pressure cap. Start the engine and allow it to warm up until thermostat opens.
If a large combustion/compression pressure leak exists, bubbles will be visible in the coolant.