Visual Test Method
WARNING: This page is about a different car, the 2016 Jeep Wrangler and 2015 Jeep Wrangler. 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.