Coolant Temperature 94°C: Why It's Happening Now.

Hello,

'The other day, when the outside temperature was 2°C, my coolant temperature rose to 95°C. This happened after a fast drive on the highway, followed by a traffic jam. During the subsequent 60 kilometers of moderate driving on the highway, the temperature didn't go back down. The heater was running at 100%. I haven't experienced this issue in similar situations during the summer.'

So far, this has only happened once, and has not occurred again.

Normally, the AFN maintains a cooling water temperature of around 90°C.

Strange?

Could it be related to the heating system? Perhaps the thermostat isn't switching on intentionally to ensure sufficient heating of the interior?


Best regards,

ObenbeiMutti wrote:

The other day, when the temperature was 2°C, my coolant temperature rose to 95°C. Normally, the AFN maintains a coolant water temperature of approximately ~90°C.

I had already recorded temperatures of 99.9°C, under maximum load and with an outside temperature of 6°C.

I suspect it's due to the thermostat in the cold water inlet.
The colder the coolant coming from the radiator, the more the thermostat closes, and the hotter the water from the engine's internal circuit needs to be in order to open the thermostat (again) to a specific degree.

Positive effect: most of the heating power is available in the winter, when it's needed - provided that the TDI engine actually reaches its operating temperature.

Thanks a lot.

It feels so good that you are all so helpful and supportive, easing some of my worries with your experience.

I am still waiting for the ZKD .

Best regards,

Is that correct, Ulf?

The G2 (which, at the time, didn't yet have the popular plateau function on the temperature display) also got hotter in the winter than it did in the summer.

m;

*Blows dust off*

Hi,

This morning, for the very first time since I've owned the car, the coolant temperature gauge showed 100 degrees!

The outside temperature was -5 degrees Celsius. I drove my usual daily route, starting with a cold start, some city driving, and then a short stretch of highway (driving moderately, with a maximum speed of 120 km/h), after which the temperature gauge almost always reaches 90 degrees Celsius at the same exit. However, today it simply continued to rise to 100 degrees Celsius. The heating system showed normal heating power on the control panel ("Hi" setting), with no excessive heat. The temperature gauge didn't budge from 100 degrees, even in traffic with the heater at full power. Regardless of the load, it remained stuck at this value.

The final check in the company's underground garage revealed that the upper radiator hose was warm along its entire length, while the lower one was only slightly warm to the touch. The engine also did not radiate extreme heat and was painlessly touchable. Squeezing the upper hose caused the expansion tank to bubble slightly, so the thermostat was likely at least partially open, in my opinion.

Now, I have some questions.

- whether I received a map cooling update via (silent) software update during the last maintenance in March.
- or whether my AI (assuming a faulty temperature sensor) doesn't even have the plateau function, which, as far as I know, only deviates from 90 degrees at 110 degrees. It shouldn't be possible for it to display 100 degrees under any circumstances.

I wasn't able to perform a more in-depth diagnostic test using VAG-COM due to a lack of equipment, but I would really appreciate hearing your opinions on the matter before I drive the 30 km home this evening.

Roger wrote:

- whether I received a

calibration update (possibly a silent one) during the last maintenance in March.
It probably requires not only different software, but also different hardware.

Quote:

or whether my AI (assuming a faulty temperature sensor) doesn't even have the plateau function, which, as far as I know, only deviates from 90 degrees at 110 degrees.. 100 degrees should definitely not be displayed there, IMHO.

Without a plateau, I believe (thanks to the cold water regulator) that you would see any significant acceleration or boost displayed on the KI (Knock Indicator) after just a few seconds.

As long as the speedometer remains consistently at 90 under reasonably normal driving conditions, you can be sure that you have a "plateau" engine control unit (ECU).

Quote:

I was unable to perform a more in-depth examination using VAG-COM due to a lack of equipment, but I would very much like to hear your opinions on the matter before my 30 km drive home this evening.

If my AI displays a value of 100, that corresponds to a real temperature of around 115°C, which is 25K above the opening point of the thermostat... In my opinion, this is not entirely safe for normal driving conditions (assuming your AI has a similar display characteristic).

It's also possible that the gauge is malfunctioning for some reason. Your test seems to confirm that.

Quote:

Even in standstill traffic with the heater at full power, the gauge didn't move from 100.

Regardless of the load, it remained fixed at this value.
This also points more towards a defect in the AI.
I can cool my engine down significantly below 90 degrees Celsius in stop-and-go traffic on a flat surface during the winter by running the heater and fan at full blast. However, it takes a few minutes to do so *sweat*.
(I don't have a uterus - in case anyone didn't know.)

Hello Roger,
I think your car's air conditioning is broken.
After warming up, the display stubbornly shows a temperature of 90 degrees; even in summer, after a slightly faster drive!
The thermostat is located 'above,' between the engine and the radiator, and it receives the coolant from the engine or the radiator.
Don't even mention the coolant temperature!
Is your refrigerant pump defective?
Best regards,
Günther.

"Thank you, I think something similar now."
So, the trip home is secured. Let's see what comes up when I check it later tonight.

Hello Günther,

Quote:

Is your coolant pump defective?????

Given the completely normal heating temperature after a 30 km highway drive, and the relatively cool engine block afterwards, it's rather unlikely.

Hello Roger,
Okay, so it's either a coolant sensor or a combination sensor; let me know what you find.
Regards,
Günther.

Hi Roger,

"Keep me updated on your progress. I'm driving the same vehicle, and my Golf has never reached over 90° (Celsius). Also, it can only maintain its temperature of 90° (as read on the dashboard) for a very short time when the coolant heater is at full power and the temperature is below 0° (Celsius). And even on country roads with low RPM, it rarely reaches a comfortable temperature and 90°."

@Ulf:

Quote:

As long as the display remains stubbornly at 90 under relatively normal driving conditions

.
She usually stays at that level, so it's a plateau. I only saw with VAG-COM that you can also code the coolant temperature sensor to use a map-based cooling calculation...

@Günther+Matthias:
Yes, I will definitely keep monitoring it. I listened to it briefly again just now, specifically focusing on the water pump. No abnormalities detected.
[Detour mode on:]
"There are rhythmic knocking/scraping noises coming from the transmission (possibly the dual-mass flywheel?), especially when the engine is cold. It happens about 3 times every few seconds. However, when the clutch is engaged or the engine is warm, the noise disappears. I'll continue to monitor it."
[End of digression mode:]

It actually always gets pleasantly warm on this route. After about 3-4 km in the city, followed by about 5 km on the highway with the climate control set to 18 degrees and the fan on its lowest setting, the water temperature, according to the car's computer, reaches 90 degrees. Then, for the rest of the journey, it's time to turn on the "heating," meaning setting it to 20 degrees with the fan automatically increasing. In very cold conditions, the car's computer display will briefly drop a bar, even at speeds of 120-140 km/h, but after that, it remains constant at 90 degrees.

Sure, here's the translation:

"Once again, @Ulf:"
This morning, I had a misjudgment: The thermostat is located at the bottom of the engine block, not at the top near the dual sensor. Therefore, the former could very well be faulty.
Unfortunately, a contributing factor is that before I could even start working on the hoses, I had about 10 minutes of slow traffic with the heating on (set to 20 degrees Celsius), and then I drove a few hundred meters through the rather large underground garage (around 3 degrees Celsius) before I could finally get to them. In my opinion, even a perfectly functioning TDI thermostat would have been closed by then.

On the way back, I'll try using the CT's self-diagnostic function to see if diagnostic channel 45 is active on my CT. Hopefully, that will also display the coolant temperature.

Where exactly can I find the coolant temperature value reported to the instrument cluster using VAG-Com? Do you happen to have the corresponding measurement block/channel for the instrument cluster?
I believe the value for the EDC coolant pump can be found in MWB 1 of the engine control unit.

Roger wrote:

The thermostat is located at the bottom of the engine block, not at the top near the dual sensor. Therefore, the former

could definitely be faulty.
A factor that makes the diagnosis more difficult is that before I started working on the hoses, I had about 10 minutes of slow traffic with the heating on (CT at 20 degrees), and then I drove a few hundred meters through the rather extensive underground garage (~3 degrees) before I could finally get to them. In my opinion, even a perfectly functioning TDI thermostat would have been closed by then.

Quote:

But even then, the AI shouldn't have displayed a temperature of 100° anymore.

Where exactly can I find the coolant temperature value reported to the instrument cluster using VAG-Com? Do you happen to have the corresponding measurement block/channel for the instrument cluster?
I believe the value for the EDC coolant heat exchanger is found in MWB 1 of the engine control unit:wink:.
If you still have a dual-sensor setup, you might not be able to easily (or at all) find the sensor value for the KI (instrument cluster) using VAGCOM - unless it's possibly located within the KI itself -> download the label file from Theresia's website. }

My Polo only has one individual sensor left. It's connected to the EDC (Electronic Differential Control), which supplies the rest of the interested systems (including the instrument cluster) with water temperature data via the CAN bus.

Hi,

All clear .

On the way back, the gauge didn't move even a little bit from 90 .
Unfortunately, the CT scanner is not receiving a signal on channel 45; it would have been too easy if it had.

Quote:

But even then, the AI should not have been allowed to display a temperature of 100°.

That's also true.

Quote:

My Polo only has one individual sensor left.

Aha, I had previously assumed it was a double antenna. You can't really see anything there.
According to my information, only the BAD and BFQ models have the individual sensor. Did you perhaps order a lightweight ASZ unit ?

I'm still going to read it again now, I borrowed a really fast notebook for the night because I was having some difficulties with the interface, and I have to go test it anyway .

I'm curious to see how it performs in a cold start tomorrow.

Ulf and Matthias, have you ever listened to the transmission after a cold start, after more than 30 seconds of idle time, as I observed above?
I know, strange hobby ...

Hi Roger,

Roger wrote:

Aha, I had previously assumed it was a double antenna. You can't really see anything there.

According to my information, only the BAD and BFQ have the individual sensors.
Document

Quote:

In my opinion, the most reliable option for such things is the appropriate SLP. On my engine, the sensor is located at the rear, underneath the tandem pump, and the connector is pushed on from the back.

Ulf and Matthias, have you ever listened to the transmission after a cold start, after >30 seconds of idling (as noted above)? }
Besides this.
I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.
"My transmission isn't making any other noises."

When the temperature is significantly below 0°C, things are still quiet even after the commute to work (~20 km of country road with various small towns).

@ Roger


also bewusst habe ich da noch nicht gelauscht. Gehört auch noch nichts. Wenn es morgen früh kalt ist fahre ich 1 Minute früher zur Arbeit und mache beim Anlassen mal die Motorhaube auf und lausche. BeSure, here's the translation:

"Please translate the following text from German to English. Provide only the translation, no explanations."


Otherwise, everything is working fine with my ASZ (hearing aid), except for the occasional "rattling" noise, but it's extremely faint and not bothersome to me.