Jeep CRD Head Gasket Cold Engine Leak Test Procedure:
1. Engine off, cold engine preferably after setting overnight.
2. Remove the coolant reservoir cap located on top of the expansion tank to release any existing pressure that is still in the system and then replace the coolant reservoir cap tightly.
3. Start the cold engine and let it run for 60 seconds (1 minute) and no longer, then shut engine off.
4. Remove the coolant reservoir cap on top of the expansion tank again and listen closely and be attentive to note if any pressure escapes from the coolant reservoir. Even the most miniscule amount of built-up pressure escaping from the coolant system after only 60 seconds of run time would indicate a head gasket leak or worse, a possible cracked head.