1999 Audi A8 4.2L V8 Oil In Coolant and Overheating in Traffic
 

Hey guys I just purchased a 1999 Audi A8 Quattro this is my first Audi it has 162000 miles and it seems to be getting oil in the coolant but no coolant in the oil it also likes to overheat in traffic but once on the highway it seems to cool back down to running temperature does anyone know what could be going on car doesn't run rough no smoke from the exhaust or the engine bay.

Could have some co-mingling of oil into coolant from the oil cooler. It is side-mounted behind the alternator and is cooled with engine coolant.

Cooling system: Two Fans. One is engine driven by a clutch at the center of the fan. The hot air passes over the clutch causing it to firm up and turn the fan more forcefully. Clutch failure will cause low airflow. See: Clutch Fan Pencil Test.

Second Fan is a variable speed electric fan. It always come on when you turn on the A/C (or it should), and it also comes on when temperatures get too high for mechanical fan to keep up. It's speed is controlled by the trinary switch. Is it wobbly af? Does it come on with A/C? Does it come on when the car is hot? Trinary switch looks like the bottom of a flattened pound cake loaf pan on edge. It's got three blade terminals sticking out the front. It is hiding on the driver's side visible from underneath, up front, driver's side, behind radiator. Clean those three terminals.

With the fans, you may have more than one problem. Both fans could be failing. Fan clutch and electric fan.

Good hunting.

Yikes. Previous mechanical experience leads me to think overheating and oil in coolant are indicators of possible head gasket leak. But before you spend big money or junk the car, sort out the simple stuff first. I echo what BrianC72gt said, check and make sure your fans are working properly. If they are, you might want to consider replacing the thermostat. I had an overheating issue on my 2000, and solved it with a $20 part. The sucky part is the stat is behind the timing belt. It can be replaced without removing the belt, I did it myself. Maybe consider backflushing the radiator, I paid $65 for a local shop to do this (turned out not to help since it was the thermostat). Does the temperature go down if you blast the heat inside the cabin?

You may also consider environmental condition: If you are stuck in traffic and the ambient temperature outside the car is 40-45C, Having the engine coolant temperature to rise a bit (let's say 105-109C instead of the usual 96-102C), it may be totally normal. If this occurs with ambient temperature of 20-30C, then you may have a problem and the solution provided above are to consider.