Hi All,
I have a 2004 X3 3.0. I live in Minnesota aka "Minne-So-Cold" We have been in a serious cold wave with night time lows of -10 to -20 f. The low coolant light came on and I toped it off with maybe 8oz. I began to monitor the level afterwards and had observed a minute loss. I observed a little coolant on top of the expansion tank like ti was coming out the pressure cap. I pressure tested the cooling system and observed a very slow depletion. I pressured the system and started the car and observed a single puff of white smoke on start up but no lingering white smoke, the car doesn't overheat, misfire nor does their appear to any water on the dipstick. The valve cover breather is a little frothy but that's normal in the winter up here. I took it to a reputable mechanic who said I should hold off on the head gasket because he said the extreme prolonged cold can be causing the miniscule head gasket leak. He explained that over thousands of warming a cooling cycles the metal in the gasket can compress due to metal fatigue. When metal in the block gets super cold it contracts perhaps .001/.0005 " just enough for a little coolant to seep through the layered gasket facilitating a little seep into the cylinder whilst a little exhaust gas passes into the cooling system causing pressurization for a short interval until the heat of combustion expands the metal enough to close the fissure.
I previously had an old 525 with an non-vanos M50 engine and I remember a BMW mechanic telling me that old BMWs tended to have minor head gasket leaks in the winter owing to the wider range in temperature exacerbating metal expansion and contraction.
Has anyone else out there heard of or experienced this ?
That’s news to me. Of course, I’ve never driven a car in weather that cold. But, I guess anything is possible. Btw, this is the E46 subforum. I recommend you post your question in the general mechanical section. That’s where the techs (bmwdirtracer, white94rx and others) respond to questions.
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