i have an astra gsi on an 03 plate. back in june the coolant light came on when i was stationary and the revs wavered up and down on tick over.....didnt do it again until 2 weeks ago. took it to vauxhall dealership and they said the head gasket has gone, although the car was running fine and no obvious signs like water in oil, overheating etc. so they did the work to repair it, however, it did it again 2 days after it had been "fixed"!!!!
anyone any ideas on what could be causing this?????