today i was driving home and when i stoped i could hear water bubbling so i opened the bonnet and found the expansion bottle for my rad was boiling and also noticed my cooling fan bolts had snapped, so i took her stright to a garage and they where unsure what could casue this, so we remounted the fan and then later on i checked and my expansion bottle was empty then i checked again and it was full and not bubbling i just got home and found it was going it again!! i did a diagnostics test and found nothing wrong except it was running a little bit rich, i have no idea what the problem could be i