My car is doing exactly the same thing. Great every day until one morning it won't crank. I took the cap off the expansion tank and it was pressurized. I hand turned the crank and when it got to the really tough cylinder, while puling (very hard) through this cylinder you can hear fluid being emptying into the crankcase.

Either the head gasket, or the head.

I've got new head bolts, now I'm waiting for the head gasket. Next wee I take it all apart.

__________________
Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)