Pretty certain one bank has blown.
Was perfect when I first got the car and then it started to lose a little bit of water after a couple of months of ownership.I thought that I had found the problem when I noticed a small leak from one of the bleed hoses....replaced that,job done I thought.
I also started to get a bit of misfire on start up which i was kind of ignoring untill the coolant level light came on again,thats when the penny dropped.
I started the car up from cold with the cap off and ran for a while on the drive.I noticed the the water level was rising in the expansion tank along with quite a few bubbles.Turned engine of and left it for ten minutes with cap of.Returned (after a cup of coffee and ***)and started engine...no misfire.Put cap on,started engine,ran up to operating temp,turned off and left for another 10 mins.
The next time it started it was missing and there was some steam/white smoke out of one of the exhausts.
My theory is that when stood the pressure in the cooling system is pushing water into one of the cylinders,causing the misfire on startup.
This car has never overheated since Ive owned it but it was stood for over a year previous to that.I know that antifreeze goes off after a while so im hopeing that the gasket has simply rotted a bit.
Is head gasket a common failure...looked through a few related threads on gasket problems but none of them come to any conclusion.
I will keep this updated as to what I find in the next few weeks and will be happy to hear your thought so far.
Thanks
Alex