I've got an Octavia 1.9 PD 4X4 06 plate. It's done a lot of miles (208K) but should be able to do more. I had the cam belt renewed a couple of months ago and since then it has been losing water. It was losing water slowly (topping up the expansion bottle) every few days. But I have now replaced the stat as it was running cold and the temperature was bouncing. My mechanic has said it is a head gasket seal gone but I am hoping it isn't. Since I have changed the stat the temperature remains stable at 90 but is now losing water more quickly and I have no heat inside the car. Having said that I do get heat randomly which suggests an air lock. I have put a new heating matrix in. Also if I run the engine with the expansion tank cap off and top up with coolant this is a way of flushing out the air lock and getting heat inside the car. There is no milk in the oil and the exhaust fumes are clean.
Does this all sound like a head gasket or could it be losing water elsewhere? The only water I can see leaking is from the expansion tank under pressure.
Thanks.