pug 306 diesel

can anyone help i have just bought a 306 non turbo deisel whicg has an overheating problem when i remove the radiator cap is removed even from cold there is water being forced out the radiator could this be the head gasket or thermostat any help would be gratefull thanks

I had a similar problem with my old 205. That was the head gasket. I would recommend changing it before it causes further damage - like warping etc...because then it becomes really expensive!