Random Overheating

A6 All/ S6 All
#1

Well, after a new engine and a new transmission and a new Coolant reservoir tank and toe links and control arms and tires and… you get the point, yet another issue is occurring with my car. This time the car is overheating when sitting for roughly 10 minutes at idle. It actually started happening randomly, when it happened had a coolant dump refilled and bubbled out the coolant system. We’re back at it again, it random and i can figure out if it’s the Thermostat or Water Pump. I know the AC went hot the last time, but lately it’s just creeped up to hot. I turn the car off for roughly 5-10 minutes and the Thermostat is back down to normal when i turn the car on. It’s a weird and random issue.

Oh yeah, and the airbag light is on, one of the sensors at the front took a poop. I swear this car has issues every 2 months, but it’ like a woman…

#2

What year and who installed-

#3

You’re not losing coolant though, right? Just having an intermittent flow problem? My car has had multiple different issues with the coolant system, but the thermostat and water pump have never had an issue. Being an intermittent issue, I suspect thermostat, but I’m sure others here are more qualified to answer that question than myself.

#4

Did they forget to plug the connector for the radiator fan back in after the engine install? Does the radiator fan kick on when hot?

If it ONLY happens when idle, that’s the first thing to check.

#5

Are you getting any engine codes?

#6

This!

And yes on codes

#7

The one big thing to note is that the AC goes warm. That has shown in the past that the cooling fans are not pulling air out or the rad unit itself is damaged.

The AC heat exchanger is in front of the rad unit. It gets super hot in hot days that heat can make its way into the main rad unit and that can bring up temps. When you turn on the AC the fans should kick on within 4 min. So you should be able to look at the fans and have someone turn on the AC. Within 4 min the fans should turn on.

What has been known to happen is that the fan motor works but the fan blades and the shell come dissconected from the mount to the fan motor. The motor will spin but the blades dont. So you dont get a code.

If you cant see the fans easy fix to test and see if the fans work is to pull the positive battery lead off and from there pull out both the ECUs from the passenger side right under the windshield. with the ECUs out put the positive lead back on the battery and put the car into acc mode. Wtih the car in acc mode and no ECU the fans will turn on full blast. The ECUs control the fans.

#8

Ironically, there are no codes in relation to the overheating. Even when the temp pegs on H no coolant light no anything.

The fans blow or at least for a while now have blown super loud, i mean the car sounds like its going to take off most of the time from the fans.

It’s a real interesting problem that I would prefer to diagnose before i take it to the stealership if i do that, ill more than likely buy a new car.

#9

Next time you have this happen try turning off the AC if its on. See if that helps. If that helps thats not uncommon.

#10

Well, happened again so for only happens while stopped for over 10-15 minutes. If I start driving the car will cool down so looks like it may actually be the fans or something

#11

That would be the direction I would have to say its pointing to. The fans are there to make sure the car wont over heat at a stand still. If the car cools down if you start driving again thats good.

#12

Yup double checked sounds like the fans aren’t kicking into high. They’re just running low, although if I turn the AC off and heat on that brings the tempt down fast as well

#13

WOW that kinda wraps it up as a fan issue or a rad issue. Not too hard to fix. Radiators are cheap if you need one and I dont know what might be wrong with your fans but I would think if you can hear the fans it might just be the controler or the actual temps sensor right by the radiator

#14

Sounds like it could be the controllers for the fans, before the damn car sounds like a plane taking off with the fans on. Now it just sounds like the fans are at a medium or low level still blowing just not as intently. Either way I’ll be looking at fans and a radiator.

Temps drop drastically as soon as i turn the heat on or AC on a setting that is above 75. Just an interesting little thing, especially since i haven’t heard of many S6’s with this issue. I swear this car will be damn near brand new after all of this work.

#15

Mine’s done that. Thermostat leaked after waterpump was done, took out some of the wiring to the fans. Twice. And still fighting with the dealership to warranty their work, less than a year out, right now. Coolant leak was so minor, the reservoir level was still good. But you could see the white traces where it was coming, and the wiring that burned up to the fans as a result. Exact same symptoms.