Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
is the oil in the coolant or is the coolant in the oil no just kidding lol maybe try a coolant pressure test it will force it out one thing to keep in mind is gasket can fail between cylinders but then you would probably see a lot of white smoke and smell coolant there are dyes you can add to coolant and or oil
The head gasket is only 3 months "old".
I will put pressure in the coolant system and I will also check for HC.
But if it is not a head gasket, the only last options are crack in block or head?
misfire on initial start up would be indicative of cylinder head leak. I would recommend warming engine then pressuring coolant system for about an hour then remove spark plugs and check cylinders for presence of coolant. Also are you seeing coolant in the engine oil or are you seeing oil in cooling system ? I ask because Nissan has had many transmission cooler issues mixing transmission oil and coolant .
All of the above --- additionally although less common than it used to be water (nb not coolant) in the oil can be a sign of the engine not getting up to a high enough temperature to drive off water from combustion.
Head gaskets and fail in a number of different ways, with the case of coolant going into the oil the header tank gas test may not give a positive result and there is no absolute way to tell an inlet leak from a head gasket leak .
" We're trying to plug a hole in the universe, what are you doing ?. "
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