s eight

last night temp went way up while driving home and warning light came. will low coolant level cause this or can it be more serious?
where can I purchsde the Audi coolant from?
Thanks

saabSean

Which warning light went off? The low coolant warning?

If it is low coolant, then yes, you can overheat. My low coolant problem went away after my shop swapped out the cap on the coolant tank.

4Driver4

Low coolant will trigger the light, but if the gauge went all the way up you have other problems. I hope you didn't drive far like that.

I'd start with a new coolant temp sensor.

SNAFU 4

If you are low enough on coolant to trigger a light... then you do have another problem. That much coolant should not just vanish, more than likely you have a leak somewhere. Check the overflow tank first. I actually had to have my radiator replaced (under warranty thankfully) for a small leak.
Also, if the gauge shoots way up it could be the sensor, or it could be you frying the engine. Stop, don't drive and inspect.
You could get the coolant from Audi or VW... water will work fine in a pinch (if you plan on flushing anyway).
Also, definitely elaborate on which warning light (low coolant or high temp) and what was your water and oil temp at during that time....

S4_Cinci (I S'edTFA)

then this is a serious issue and can kill the engine in short order due to sludge formation. You can usually smell the coolant if it is leaking outside the engine and onto a hot surface. Expansion tanks will leak sooner or later and they are relatively cheap to replace.

s eight

temp light / 4.2 engine

SNAFU 4

Hopefully just the sensor then... but keep a close eye on it while driving it to a shop...

twinturbo_808

On older A6 models (mines a 01 2.7T), the secondary pumps tends to go. Check under the manifold with a flashlight to see if there is a leak.