Don't band aid the beast. Do it right! You never know when it will need the full cooling capability. Especially if you indulge in spirited driving.

My 1989 200 QT with 350,000 miles never had a problem once the thermostat was changed. The 1988 90Q with 199K likewise and my two A6s 96 and 97 also.

 

I do love my spirited drives. ITs such a crazy thing this temperature drop. Its is nothing elctrical the characteristics of an electrics would be all the time or nothing at all. The whole needle thing started in june this year. Despite the warm temperature in the summer the car was still not running warm. Gauge and the seperate diagnostics both report the same temperature i know the garage tested this back in july.

Since i have changed the thermostat i have noticed it takes longer to get to temperature than it did before. Sometimes not at all. I know of the old mans trick with a newspaper infront of the radiator my dad used to do the same trick and i used to with an audi Coupe GT 5s. Those 5 cylander engines it was a pain i suffered from a different kind of running to cold them. Suffered incredibly from a frozen carb.

I think in this case the problem has to be circulatory with the cooling system. A few people including the mechanics think its not. They dont know what it is. But i am thinking there is an air pocket and since the heater matrix gets involved it has to be somewhere there. I have seen on a workshop manual that there are 2 bleed valves on the 2 hoses leading to the heater matrix in order to release air. It is also mentioned in the refilling steps after draining the system. I think that would be a good place to start of if the garage could refil the cooling system using a sealed radiator flushing tool.

I have had a look for the bleed valves not sure what they look like. I did find 2 pipes on the drivers side with what look like car tyre valves when you take the cap off. I doubt its this. Audi would not have made it that easy???? I actually think that what i found is the AC charging point to refil the AC system.

I wondered of the possibilty that the AC heat exchange unit was still operating ie stuck on and if it was near the heater matrix that i was cooling air i wanted hot and thus cooling the system more but since i get very hot air and it continues even when the ECON is off i doubt very much its that.

Still leaves me with air pockets i think.

 

Hi all,

More of an update.

Doubt its an air lock. Just heard the electric fan cut in.
Engine temp was at 70 had only been driven for about 5 mins. As i pulled up on the car park at work i heard it come on shocked as car was not at temp. Heater was on though. Turn off the ECON and the electric fan stops.

Hmmmm

Any thoughts temperature sensor or heater controls???

 

We did it - changing termostat helped. It heats up to 90 and stays there. Spent 10 mins hand working (do not get me wrong :-)) to get all air out. OOHHH... AAH is not an easy engine to change it.

About the channel 51 on the A/C - it shows actual coolant temp in celcius, but on mine car it goes not from a real temp sender, but is calculated.

 

All,
Have checked the car over Thermostat works ok starts to open at 87oC and fully open at 102oC. Bleed and refilled system. No air locks. They have checked the car over with an infared thermometer. Radiator gets evenly warm as do all pipes. There is a very small difference in one of the pipes leading to or from the heater matrix. Diagnostics have revealed nothing. The temperature sensors report no faults all electric fans operate as they are meant to.
In the end the garage has passed it back to me to try an engine flush with an audi flushing agent. One thats not stocked on the shelf. The reeled of a technical bulletin titles engine not getting to temperature and particles in the coolant. There was no particles in the coolant with my car.
So Not Thermostat.
Not Water pump.
Not Temperature sensors.
Not Air lock.
Any ideas???

 

Given your latest input the car should run at a minimum of 87C once it has warmed up. Either the coolant is by passing the thermostat, being forced thru it, or being held open by something. There is no other way for the motor to cool unless you have an air cooled motor which is highly unlikely.

How did they test the thermostat?? Did they remove it from the car or do some type of insitu test?

 

Did you check coolant temperature gauge in the cluster? There is a testing procedure for it as well, basically giving it different resistors. Also you have (!) to check voltage stabilizer!

 

Hi, Did you ever resolve your query as I am having the exact same problem on my Audi A3 SLINE. I have been backwards and forwards to the Audi dealers and they can't figure it out. They are now saying they would have to strip my car and that could cost me quite a bit. All the work you have done on your car I have had it done on mine. Can you please let me know. Thanks.

 

im having this exact same problem on my audi a3 sline too.... changed thermostat sensors water pump etc...

anyone find the reason and is it doing any damage to the car driving at like 60-80 degrees.... someone suggested it might compensate by using more fuel which might damage the cat?


cheers
Richie

 

My 2012 Audi A6 2.0t does exactly the same thing. I’m about to change the hidden thermostat to see if that works. 🤷🏻‍♂️
I changed the inline thermostat. $30 bucks on Amazon. Google “Audi hidden thermostat” to see what it looks like