Overheating! The cooling system started to boil from the header tank cap and noticed a LOT of coolant below the water pump. The local (trusted) garage confirmed a water pump failure and replaced it, along with a thermostat.
Ever since, I have the oddest problem. If I potter around locally, the car seems fine. If I go on a MWay, it over heats and boils over from the cap. I have blead the system from all three points and don't think I have any air in it. But I have found a pattern, can anyone help me understand what is going on please?
On hard drive, the cabin heater goes cold just before / at time of the system overheating - it is a good warning that something is about to happen
On test, at the house, I have noticed that all seems fine with the coolant circulating and returning to the expansion tank at low revs. Above 3K revs, the coolant return to the expansion tank stops, the expansion tank "fills up" and starts boiling through the cap.
I am starting to think local pottering is fine because the engine isn't really running at >3K revs much and therefore the fluid is circulating the system, but on MWay that its revving high - the coolant isn't circulating and the thing overheats.
Has anyone else experienced this? What could be the cause?
Please help. Many thanks for reading.