Q: Audi S8 2009 v10 overheating when idle

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My 2009 Audi S8 v10 (with 120k km) recently started running hot.

-When driving constantly, the temp gauge shows a normal 90C (12 o'clock position). -However, in stop and go traffic, traffic jams, at traffic lights, etc. it occasionally goes above 90C. Not much, barely to the next line, not above 110C. This doesn't always happen in stop and go traffic/ traffic jams/ traffic lights. Only sometimes. It never did this before, though. -After a 40 minute drive, when I park the car and the engine is still running, in idle, the front of the car is much louder than it used to be.. that fans are running very loud, and the grill in the front is very very cool (probably because of the intense fan speed?) -When I turn the car off, sometimes the fans stay on for 10-20 seconds, but mostly they just shut off along with the engine. -No engine warning light ever came on.

-Can I still drive it if it stays under 110C? How can I test myself what the issue is? Fan? Thermostat? How?


My car has 120000 miles.
My car has an automatic transmission.

Once operating temperature reaches approximately 220 F, you’re really considered at the limit. It sounds like you are occasionally above that so do get this resolved as overheating is a principal cause of shortened engine service life and can cause acute damage, too. Thermostat failure is not unusual. Indeed, it is not a bad idea to just replace the thermostat outright based on mileage. You could try that first but test the thermostat after you remove it, so you have further info if you need to continue with an overheating diagnostic (i.e., if the thermostat tests as faulty, that may eliminate the need for additional diagnostics). Buy and install ONLY a genuine OEM thermostat from the new car dealer to reduce diagnostic headaches. By the way, overheating will itself damage the thermostat and if a car has overheated the thermostat is automatically replaced.

The most common causes of overheating include low coolant level (including that due to leaks), a faulty thermostat, a plugged radiator, a faulty radiator pressure cap, collapsed hoses, non functioning cooling fans, and a faulty water pump or drive belt. Certain engine faults, such as a leaking head gasket, poor engine running condition or exhaust blockages can also cause overheating. If you desire that this overheating problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, please request an engine overheating diagnostic and the responding certified mechanic will get this resolved for you promptly. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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