Q: Is this problem the thermostat or blown head gasket?

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I was driving down the road and my check gauges light came on. I pulled over and my radiator cap was sitting loosely (radiator cap blew off) . It would crank back up (barely) but had a rough idle. I had it towed back to the house. I drained my oil and antifreeze and neither have water or anything abnormal. My buddy said head gasket and another said thermostat. Please help me determine

Hey there. Test to see if the head gasket is blown the cooling system will need to be pressurized using a cooling system pressure tester to put pressure on the cooling system to see if it holds pressure. If it does not hold pressure and no external leaks are found then the head gasket is leaking. If no leaks are found the a combustion leak check can be done by using a coolant tester that is held on the radiator opening with a special liquid in the tester that changes to a blue color if engine combustion gas is getting in to the cooling system. This would indicate a head gasket leak or cracked cylinder head. If both of these tests are okay then test the radiator cap and replace the thermostat. If you need to have this looked at by a professional, a certified technician from YourMechanic can come to your car’s location to inspect the potential overheating issue.

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