This car only starts to overheat when going up a steep grade (the grapevine) at temperatures over 90 degrees, or sitting in traffic at temperatures over 100 degrees. It uses a small amount of coolant every 1000 miles (4oz.), and has always had factory coolant in it. I make it over the grapevine with the AC off, in 4th gear at 60mph (approx. 3500 rpm), with slight overheating (1/8th inch over normally straight up) and then the car is fine, with no visible coolant loss.
Any ideas out there?

 

I'd check the aux cooling fans - the electric ones on both sides of the radiator. If they don't turn on, the temp can go up. Could be the fans themselves, the fan control module, or the fuses for the FCM.
Jim

 

The fans work, but at 185k miles, they may be getting a little tired, as may the radiator.
The engine has been doing this since I moved to LA for grad school last fall. It was never a problem in Northern California.
Is there an easy install upgrade for one or both fans?
Jeff

 

I would be interested in finding out what is happening to your car. Mine does the same thing, but it was never serious enough for me to really get into it. BTW, so far, I replaced the radiator and the fan clutch. The secondary fan comes on fine. One of the thing that I noticed was that the coolant overflows for a brief second once in a while at operating temperature. (I loose about an ounce every month.) I am thinking that the thermostat is acting up. But for now, it only happens once in awhile and never goes above 1 click. Also this happened when I was going up the grapevine at 90 degrees with the AC on. So I will keep it this way for awhile until it gets worse.

But if you sort it out, then please share. If I do, then I will as well.

 

I'm thinking there is some slight restriction in the water or oil cooling systems.
I have replaced all of my hoses, both to the radiator and around the engine. Replaced the reservoir 50k back, and the thermostat was replaced a long time ago with the timing belt and water pump.
I'm pondering doing the timing belt, thermostat, water pump, etc., myself this summer. It depends on what the local Ingolstadt West shop will charge.

 

Expect to pay $1200 and up from a reputable independent shop who knows what they are doing for a timing belt/water pump job. Cam seals and crank seal is a must.

 

wow it seems we all have the same issues with our A6 just different areas and models. I have the 4.2 from 2002 and when we hit the 101 F record in Colorado I was also driving in stop and go traffic through the city with the AC on. My temp gauge almost reached the first bar over where it should be.
I have also replaced the coolant lines, coolant reservoir, coolant temp sensor just a few thousand miles ago due to leaking issues. Now it doesn't leak as far as I can tell. All fans turn on and run continuously during this heat.

The only thing I have recently noticed is a tiny leak from the waterpump that was replaced about 50k ago (however not enough to actually see a difference in the reservoir).

I wonder if Audi's are just not designed to run in this kind of weather.

 

@Hxgaser. I had the timing belt/water pump/cam seals and crank seal job done 85k ago by a reputable shop in NorCal. The RR cam seal blew a month later at 70mph, and blew 5 quarts of oil all over the bottom of my car and the freeway. They replaced the seal, but 3 months later it started to drip again.
I waited a year, and took it to another reputable shop in NorCal, and had the cam seals and crank seal redone, and a month later it blew the crank seal and caught on fire. They also repaired the car for no charge, and it hasn't leaked since.
I am a decent mechanic, with 30 years experience, so I'm thinking I can probably do it myself. I've replaced the timing gears on my Saab Sonett with no difficulties.

 

@ Sheldon. They sure do drive well in the winter!

 

For the love of god, I really didn't need to read any of that. I drive my 2.8 waiting for something to go wrong as it is already lol.