I got my audi 2.8 a week ago and it is overheating now. the oil temp gage was acting erratic (going from zero reading to 3 quarters and then back) so i popped the hood to put oil in/ check oil and the coolant was boiling in the overflow tank and the tube coming up to it even though the coolant temp gage was right in the middle. thanks experts

 

Was any work done on the car recently, prior to you buying it? Info like that can help us narrow down what might have caused this. In the meantime, close up the system, Jack up the front end of the car, and run it until it gets 3/4 of the way to overheating (or until it starts boiling). Then shut it down and let it cool. When it's safe, pop the cap - this is called burping the radiator. If you have air bubbles in the system this will get them out. Let us know if anything was done on the car though. You may need to change the coolant temp sensor or thermostat and flush the cooling system but we will hold off judgment until you tell us if you know about any recent underhood work on the car.

 

+1 on letting us know and doing the burp. I'm no expert on radiator systems, but it seems to me like you may have a clog somewhere that is preventing the hot fluid from getting to the radiator to be cooled. What color is your coolant? If it isn't a soft pink color, chances are someone's mixed it with regular green coolant in the past and you're experiencing the horrors of coolant sludge.