BMW: Antifreeze & Engine oil mixing, coolant tank, gasket material

Question
I have a 1991 325i that has been going through antifreeze like like it is candy.  It started about a month ago, i had to put some in when the sensor like came on.  About five days later it came on again.  I thought it was weird but filled it up anyway.  Now i have to fill the coolant tank every two to three days.  The last time i filled the tank it looked like i had engine oil in the coolant tank.  So i checked the oil and i also looks like i have coolant in there.  The car sounds fine and has been running just tad over the normal heating range.  What could be the cause of all this?

Thanks
J. Moss  

Answer
J. Moss,

 Unfortunately it sounds like you have a blown headgasket or possibly a cracked head/block.  I would put my money on the headgasket though.

 There are tubes that run from the block into the head that carry oil and coolant.  This is to cool and lubricate the head and valvetrain.  In order to keep the coolant and oil in their correct tubes, there is a gasket between the cylinder head and block.  It has holes cut into it that match the cooland/oil passages and allows it to pass while sealing around it.  If your engine has run hot (the usual cause for a blown headgasket) it warps the head an leaves a gap between the head/block.  When this happens the pressures inside the cylinder escape through the weaker gasket material, and usually break the seal on the oil/coolant passages.

 So now you have the oil and coolant passages where they can mix together.  It's obviously not blown very bad, since the engine continues to run.  The main problem is that you have coolant in the engine oil.  This is not good, since all the internal parts of the engine are metal.  I would pull the head off and replace the gasket ASAP.  If you are capable of this job, you would be looking at a couple hours of work to replace the gasket.

 Good luck,
 Josh