Hello, today I had first long trip in my 2007 a6 3.0 Tdi. It was all fine for most of it,but when driving back ( after about 200 miles) coolant warning light came on, bleeped few times and disappeared. So I stopped at the petrol station to check on my coolant level and it is fine. 2 minutes after I drove off it came back on again , this time it beeped like 3-4 times. Any ideas what could it be?