Visual Test Method
WARNING: This page is about a different car, the 2008 Dodge Magnum, 2008 Dodge Charger, and 2008 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.