My Jeep has been losing coolant before and after replacing a leaky radiator. block test proved positive for combustion gases but the dealer doesn't find an issue with leak down test. there is not coolant in the oil and vice versa. Does anyone know what this might mean? service manager said he's getting his 'engine guy' to look into it. he thinks they will find a warped piston head. If that were the case, wouldn't that show up with a leak down test? I'm still under the 100,000 warranty so that's good. Thanks in advance.

  • Sometimes the leak does not occur until the engine is hot and engine is running, so leak down tests are not always conclusive, if you have combustion gases in the radiator, you have a bad head gasket or cracked cylinder head, it need to be repaired. – Moab Jul 12 '18 at 21:03
  • Welcome to Motor Vehicle Maintenance & Repair! – Pᴀᴜʟsᴛᴇʀ2 Jul 12 '18 at 21:29
  • Exactly as @Moab states about combustion gasses. The only way for unburnt hydrocarbons to be present in the cooling system is if there is a head gasket leak which allows leakage from the cylinder. There is no other explanation for it (unless someone put oil in the coolant, but we'll assume that hasn't happened). Take it back to them, or better yet, take it to another Jeep dealer and tell them your issues. If the test shows positive, there's a head gasket leak ... no doubt in my mind. – Pᴀᴜʟsᴛᴇʀ2 Jul 12 '18 at 21:33
  • thanks so much for the replies and advice. that's what I thought from my everything I've read online. Its still at the dealership. The service manager was saying they may find a warped the head that was caused by over heating. I assumed he was trying to imply I did something wrong. One more question, could the pressure from the gases cause the original leak in the radiator? – John Good Jul 13 '18 at 13:41

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