Yesterday, the engine coolant warning came on, and required 1.5 litres to fill back to max. So, driving to Audi this morning for a pre-arranged visit to look at a different issue (problems when sitting in traffic for some time), the engine coolant warning comes on again (around 2 miles) I carry on to Audi, keeping an eye on the temperature gauge, and by the time I get there (around 5 miles) there is steam pouring out of the engine bay. Audi have just said the waterpump has failed, and a new one is required, but the part is on back order. Has anyone else here had a waterpump fail? Is this common? Mine is a 10 plate S4.