Hi XT660Z owners

My first post, mostly been trawling. But now my trawling has produced no results.

Got a 2010 XT660Z with 16000km's a few months ago. Done about 7000km's on it and did a 350KM's offroad stint yesterday. Got home and started cleaning the bike for the next days use.

Found the coolant bottle cap/plug pushed out, but luckely not lost and I can see that all the water was pushed out as as well. The water was a brownish colour. Can see hot coolant stains on the adjacent coolant pipe.

I refilled with Motul coolant and drove 75km's to the office this morning. I can see water was pushed out again. It was a cold morning and it is winter here (South Africa), so it cant be from over heating.

Checked the oil and it is clean as I changed it 2500km's ago. Bike is sitting on 22600km's. Symptoms suggest head gasket, but not through to an oil channel, just a coolant channel. I am hoping that is not the case, perhaps an air lock or somehting.

Anyone experienced this...

Dean