Rebabal

I have a 2013 S6, ~50k miles. I drive to and from the office, 23 or so miles one way, mix of highway/city. I don't drive with a lead foot and I don't drive it hard. About two weeks ago I was on my way back from work and the dash lit up saying that I needed to pull over asap, and let the engine idle without moving. I was going about 70mph. I pulled over, the engine temp gauge was all the way up and hit the red section. I let it chill out on the side of the highway while I got my OBD11 out to read any error codes/etc & see what the temps were. I don't remember exactly, but I read the inlet/outlet of the engine/radiator and one was 215ish+. I forget which one, though.

It eventually cooled off so I got back on the highway, driving about 50mph to get to the next exit so I could pull over properly. After about 30-40 seconds it went back to the red and started to yell at me, at this point I was very close to the exit so I pulled off and ended in a parking lot. I checked the temps and they had reached 225-230, I could hear the coolant boiling within the dash/heater core area. I opened the hood and noticed it was lower than normal on coolant, but just at the LOW section. I saw a slight amount of coolant (droplets size, not a lot) around one of the hoses. Nothing underneath the car. OBD11 showed no faults except for a HVAC error: 0247 "Function Restriction due to faults in other modules".

The shop I had my car towed to spent the better part of a week trying to reproduce it, without being able to. Idling, driving hard/easy, nothing did it. They performed an overnight pressure test and it only dropped 3psi, they said that was fine and no indication of a leak, and that my droplets I did see was due to over pressurizing from heating up.

I am a little anxious in driving my car now. Without knowing what caused it, I am worried it will happen again and leave me stranded or potentially with damaged internals.

Notes about the car: I had just installed APR downpipes the weekend before this happened. It was a pretty straight forward install so I can't really tell if I did anything to cause this. Aside from O2 sensors throwing efficiency codes it's been driving fine. It drove to work a few days with the downpipes on prior to overheating. I've had it back for a week and haven't had any issues.

Thoughts?

Cliffnotes: Car's overheated, shop can't reproduce it. Just installed downpipes. Don't drive it hard.

Rebabal

Can I not edit my own posts? Anyway, I searched and saw this: https://www.audiworld.com/forums/s6-.../#post25226179 regarding a TSB... this looks to just be a software update... is there a way to see if this has already been performed with OBD11 or something?

gk1

I know nothing about OBD11 but in VCDS if you go into the Engine module you will see the part number like 4G0906014B and then the software version 0008 if yours was updated.

Rebabal

As it turns out, the radiator tank main hose at the bottom is leaking, or the tank itself is leaking. I think the reason the shop was unable to replicate the issue was because they topped off the fluids. Since having the car back and cleaning the surrounding area (and driving in a few miles to test it out myself) I'm seeing pink fluid in and around the wheel well. After investigating, I noticed the bottom of the tank where the hose attaches was wet. I also noticed this when the car broke down, but assumed it was from getting wet due to fluid spraying around from overflowing. I dried the area with my air compressor and watched it slowly wet itself again.

I assume that, over time, it leaked enough radiator fluid out to overheat at that fateful moment, and temporarily resolved itself when topped off.

Now i'm trying to diagnose whether or not it's the hose or the tank, because the hose is attached to a hard line directly below the brake line distribution block and looks like a PITA to reach with pliers. Either way, I believe it to be resolved one way or another.

PS: can I really not edit my own posts?