Home › Forums › Stay Dirty Lounge › Service and Repair Questions Answered Here › Ls swap issue › Reply To: Ls swap issue April 20, 2020 at 12:04 am #954365 Richard KirshyParticipant Suggest you first try a combustion gas test to see if you truly have a leak somewhere between the combustion chamber(s) and water jacket. Might also try a new radiator cap.