Coolant Temperature Audi 100 2.5 TDI

Hi,

A few days ago, I started a thread about the Audi 100 2.5 TDI (AAT), and you all helped me a lot with your experiences!

Now, as of today, I own one of those cars.
I am very satisfied.
I still have one question.
The WATER TEMPERATURE DISPLAY almost never exceeds approximately 60-70 degrees Celsius.
The workshop at the VAG car dealership where I bought the car says that this is normal for the older AAT/AEL engines – they are very difficult to get up to temperature.
It took a while for my Golf 3 (1Z) as well, but eventually it settled at 90 degrees.
So, is the radiator thermostat defective in my Audi?

I'm especially thinking of Hannes, Marko, Christians, and Bertil, who have experience with the car!

Thank you!

Hi,
While it takes quite a long time for the engine temperature to reach 90°C in winter with my C4 (AEL), it only takes a maximum of 5 to 7 km (in the city) during the transitional seasons or in summer.
However, the coolant temperature gauge likely displays the temperature of the external circuit; if your car has an automatic climate control system, you can display the temperature of the internal circuit in diagnostic channel 51. This value will increase much faster than the pointer on the analog instrument.

Olli.

Hi,

I would call that a prompt response!!
Sorry that I forgot about you up there .

Yes, I have the climate control system.
Can you briefly explain again how the diagnostic channels work through the Climatronic system?
I've heard of it before, but I don't remember the details.
Make me smarter!!!
Can you also, for example, use it to query the oil temperature?

Alright then.
To activate the diagnostic mode, you need to press the top and bottom buttons simultaneously from the buttons located on the right side (specifically, the upper vent and the recirculation button).
Using the temperature control buttons, you can select the diagnostic channel (I believe it's channel 61). Pressing the recirculation button again will then display the value of the selected diagnostic channel.
The oil temperature cannot be read, but the engine speed, vehicle speed, and all valve positions, as well as intake and exhaust temperatures, can be displayed. I used to have a list somewhere that showed the channel assignments, but it seems to have disappeared.
The new climate control system has a few more channels, but the meaning of the channels that were present in the old climate control system is largely the same. You can find documentation about this, for example, in the FAQ on audicoupe.de. If I happen to find the codes from the old climate control system, I can send you an email.

Olli.

Hi,

Okay, I have the list from audicoupe.de.
I'll try that out tomorrow.

Hi,

You wouldn't believe what can be hidden on a hard drive... :)

Check out.

http://www.audiworld.com/tech/int5.shtml

There's proper documentation available for the 'older' climate control system.

Olli.

Hi,
It's true that the 5-cylinder engines take a while to warm up. The exact time depends on the outside temperature and driving style (power demand). However, with the current mild weather, 15 km should be sufficient. My engine temperature eventually settles around 90°C.
Generally, the temperature gauge in cars is not a precision instrument and can sometimes malfunction. You can roughly check the thermostat by touching the radiator or its hoses when the gauge shows 60°C. They should then be noticeably cooler than the engine block. If everything was cold beforehand, the radiator should be cold, and the hoses should only be warm near the engine.
It's quite tight in here, so turn off the engine and be careful of a built-in electric fan.

Hi Markus!

I can only agree with the statement made by the previous speaker.
It's the same for me, but mine has been reaching operating temperature a bit faster lately. I'm not sure why.
It might be related to advanced key management features.


Best regards: Marko

"Mine is also warming up faster than before. Specifically, it started right after the last timing belt replacement. Because it now starts up really well, which was a problem before, I think the injection timing wasn't adjusted correctly during the last belt change."

Hi,

Thank you for the information.

I paid close attention to the temperature again today.
Even after a significant amount of battery charging, the display temperature remains close to 70 degrees Celsius.

Then I ran the test again using the diagnostic channels of the automatic climate control system. In that case, the maximum value was 84. However, it mostly fluctuated between 70 and 80.

Well, it looks like I'll probably be using the Audi used car warranty for the first time...

Hi,

I just took a quick 'gut feeling' test.
1.) Cold start.
2.) After driving approximately 4 km (through a small town), the radiator was touched and felt cold.
The thick coolant hose running from the engine to the radiator was located near the engine.
Quite warm, but cold right next to the radiator connection.
3.) After driving approximately another 4 km, you'll encounter the same situation again.
Cooler this time = warm.
Hose = very warm.
-> It seems that the thermostat is already opening/closing in some way.

The strange thing is that the temperature display hardly moves, reaching a maximum of 60 degrees.
It could also just be that this display is defective.
Channel 51 of the climate control system usually displays a value of 76 (degrees) when the engine is warm.
But never around 90!!! Is that also too little?

Hi,
The temperature seems a bit low to me.
I've heard that there are thermostats that open a bit later; perhaps they were also installed as standard equipment from a certain date onwards, so that people wouldn't have to freeze quite as long in the car during the winter.
However, if the thermostat is completely closed, then there probably isn't a defect, as I can't think of any logical explanation for why the opening temperature should change over time.

Olli.

Hi,

Okay, then I'll just take it easy for now and wait out the winter.
If I then have to build a campfire in the car to avoid freezing, that part will be replaced!

Based on my own experience, I can say that the temperature sensors in all 5-cylinder engines (whether gasoline or diesel) are quite prone to failure, and after a certain amount of time, they start displaying incorrect temperature readings. If the temperature doesn't increase even under full load, I would definitely contact the dealer about the used car warranty.

best regards

Hannes.

Hi Markus,
I can give you some comparison values.
This morning, the outdoor temperature was approximately 10°C.
After approximately 1 km, the temperature display in channel 51 of the climate control system showed 50°C, and after 7 km, it had reached 84°C.
The oil temperature gauge (analog) read approximately 75°C, and the water temperature gauge in the combination instrument displayed approximately 80°C.

Das ganze bei relativ gemütlicher Fahrweise, also nicht viel über 2000 Umdrehungen beschleunigt und dann etwa 1600 Touren im 4. Gabbreviations
If you demand proper performance, it also warms up faster, but somehow I resist doing that with a cold machine :).

"At a leisurely highway speed (approximately 130-140 km/h), the temperature display in the climate control system remains fairly constant between 88 and 90° Celsius, and the display in the instrument cluster also stays at 90°. However, if you drive a long downhill section at low outside temperatures, the display can drop to 75 to 80° Celsius."

The coolant temperature display on the climate control system seems to be using a sensor located in the inlet to the heater core. At least, I've noticed that when the outside temperature is higher than the temperature set for the interior, the display doesn't go above 50°C. Similarly, in winter, when the system is still relatively cold, it probably doesn't release the full heating power until a minimum coolant temperature is reached.

Olli.

Hi,

Because that low mileage listing made me feel uneasy, I decided to visit another Audi enthusiast today.

He gave me a (not entirely unintelligent) alternative suggestion:
He says that it is not the thermostat that is defective, but the sensor that supplies the temperature reading to the instrument panel in the cockpit!
Because when the engine is cold, the radiator also remains cold, so the thermostat is closed. However, if I let the engine idle for a while at 3,000 RPM, the temperature gauge still doesn't rise, even though it should if the thermostat were stuck in the open position - because in this test, every engine gets hot! In my case, the analog gauge stays at around 70 degrees, and the digital display of the climate control system shows a maximum of 80 degrees.

I'm going to cause some trouble for the dealership that sold me the car on Thursday; I've already threatened to do so.