Low coolant levels
If you notice that the coolant levels are low, depending on what engine it is, it could be one of two problems. If it is the 3.2 petrol model, it will be because of failure of the coolant pump. On the 3.0 diesel engine, it will be because of failed EGR valve coolers. Whether it is the diesel or the petrol, the problem part will need to be replaced.
Air-con not ice cold
If the air conditioning is not blowing out ice cold, it means your air con system needs a re-gas. You will need this done by a professional. There are kits you can buy from places such as halfords that claim to do as good of a job, but these have been met with mixed results.
Multitronic gearbox problems
If you are having issues with your multitronic gearbox, such as hesitant gear changes, it probably means your car needs a software upgrade. Contact your local Audi dealership for more information, they will be able to tell you if your car is due a software upgrade.
Some owners have reported a short clutch life on the S5, although many experts and other owners believe this more down to the specific drivers shifts and launches, this is a problem across the Quattro range.
Carbon Build Up
A lot of owners have complained of carbon build up in the engine, this can sometimes cause rough running and make the car slightly lack in performance. Many garages now offer a service such as ‘Terraclean’ which clears out any carbon in the engine through the exhaust.
I would recommend Engine Carbon Clean over Terraclean. As its introduced in the air intake rather than the fuel rail.
I had an engine carbon clean done …. Brings life back to the car that you don’t even realise you’ve lost
Not entirely sure which one mate to be honest , however it made a really noticeable difference on my 3.0 tdi