Water = 100°C at the source, but only 13°C outside!!

Hello,

In my liquid level temperature logs, the coolant water temperature is also included as a byproduct.

When I looked at them the other day, I was quite startled at first.
When driving in the 4th gear at full throttle up to approximately 4300 rpm (about 170 km/h), it rises up to 100°C, and that's with an outside temperature of only about 13°C .

Since the thermostat is likely already fully open, the cooling system is probably operating in an "unregulated" state, where the temperature difference between the engine and the outside air remains relatively constant.
According to that, I would expect a coolant temperature of approximately 120°C in the same operating conditions with an outside temperature of 33°C.

Is that normal?

If so, this appears to reveal another purpose of the plateau function in the coolant temperature gauge (between 75 and 110°C, a constant 90°C is displayed): namely, to avoid alarming customers with strong temperature increases during short bursts of full throttle.

Interestingly, the thermostat seems to be located not at the engine outlet, which is typical for Volkswagen, but rather at the cold water inlet from the radiator to the engine block.

Hm , Thermostat saß schon in meinen ALH-Zeiten 'Kaltkühlmittel@Kühler' -> Motorblock. BeThe same applies to AWX.

I would consider the temperature to be quite unusually high. Mine typically ranges between 86 and 93°C, regardless of operating conditions. However... I have a viscous fan coupling, and the climate control is constantly set to 'Auto,' so it's continuously blowing at least one fan full of cool air into the engine compartment.

by the way
My chipped ALH engine, even with an oil temperature of around ~118°C, rarely exceeded a coolant temperature of 95°C. And achieving that 118°C oil temperature required a good amount of full throttle driving...

Possibly your thermostat or coolant sensor is faulty.

Sure, here is the translation of the text from German to English:

'btw2/' translates to 'by the way, part 2'. It is often used in online communication to add a comment or thought that is related to the previous conversation but not directly relevant.
Starting at 110°C, the gauge needle for the coolant, along with a warning message on the instrument cluster, should stop moving, or has this been changed in the 9N model?

Julian wrote:

Possibly, your thermostat or the coolant sensor is faulty. Sure, here is the translation of the text from German to English: "btw2/" translates to "by the way, part 2". It is often used in online communication to add a comment or thought that is related to the previous conversation but not directly relevant. From 110°C, the gauge needle for the coolant, along with a warning message on the instrument cluster, should stop moving, or has this been changed in the 9N model?

Yes, starting at 110°C.
It was still missing 10 degrees to reach that point.

The warning (sound and indicator light) in my car doesn't come on until just before 130°C.

I'm going to remove my thermostat and test it in a water bath.
According to the repair manual, it should start to open at 85°C and be fully open only at 105°C – can you confirm that?

Considering that the valve is located at the hot water outlet and the thermostat is at the cold water inlet, things might become a little clearer...

Hi!

Opening temperature at AWX: +87°C, closing temperature: +102°C.

The thermostat must move approximately 8 mm between its starting and ending positions.

However, the opening temperature is usually printed on the thermostats themselves.

Sure, here is the translation of the text from German to English:

'edit'
Do you have a cooling system that's controlled based on a characteristic map (or lookup table)?

Hi,

Did you only accelerate rapidly multiple times, or did you also maintain that speed for a longer period? If it was the former, I would consider it perfectly normal and suspect that it might decrease somewhat once the airflow has had a chance to push a sufficient amount of air through the radiator.

I've never logged any data on my own car while driving on the Autobahn, but based solely on the oil temperature, I would suspect that the water temperature also doesn't remain constant at 90 degrees Celsius. After about 20 to 30 kilometers driven at approximately 200 km/h (which is full load for the ASV engine) and with an outside temperature of around 20 degrees Celsius, the oil temperature was actually 131 degrees, but it remained very stable after that.

At partial load, it took a very, very long time for the waste heat to reach 100 degrees Celsius.

"@Ulf: Why don't you just do a comparative test with the Ibiza to have a comparison under similar conditions?"

Best regards,

Jan.

Here are my logs, most of which were recorded at an outside temperature of 25°C or higher.


CLICK
CLICK
CLICK
CLICK


Sure, here is the translation of the text from German to English:

'Cu Gremlin'

Julian wrote:

Opening start at AWX: +87°C, opening end: +102°C. You don't have a map-controlled cooling system, do you?

Thanks for the data – I think that because of the 25 Nm difference, the AC unit probably won't have a different thermostat.

My cooling system is quite old-fashioned and uses a water pump and thermostat.
"I have two electric fans on the radiator and also an LED that indicates when they are switched on, but unfortunately, they still spin due to the wind at speeds of around 70 km/h."

If it's lit up, that doesn't necessarily mean the fans are electrically powered...

Jan6K wrote:

Did you only accelerate rapidly multiple times, or did you also maintain that speed for a longer period? If it was the former, I would consider it perfectly normal and suspect that it might still decrease slightly as the airflow has a chance to push a sufficient amount of air through the radiator.

The temperature rose from 93 to 99.9 (°C), effectively reaching 100°C, within approximately 90 seconds while operating at nearly full load in the fourth gear.
Speed approximately 3000-4300 rpm = 120-170 km/h, with most of that time at around 4000 rpm.

@gremlin:
In your fourth link, the temperature also increases within about 1 minute from approximately 90 to 97°C. If this trend were to continue, it would likely have risen to 100°C or even higher.
However, it's tropical heat here instead of the 13°C I have where I am.

@everyone:
Could it be that the impeller blades of the pump are broken or damaged (e.g., they may have fallen off once before assembly), and that's why the pump isn't delivering its normal flow rate?

How could one check this, other than disassembling the transmission (ZR) to access the pump ?

@gremlin:
In your fourth link, the temperature also rises within about 1 minute from approximately 90 to 97°C. If this trend were to continue, it would likely have reached 100°C or even higher.
However, it's tropical heat here instead of the 13°C I have where I am.



and at full load and a 15% incline, with partially open throttle and a speed of 50 km/h!
AND of course WITH Climatronic set to the coldest setting.

Sure, here is the translation of the text from German to English:

'Cu Gremlin'

Hi,

@Ulf:

Quote:

"I have two electric fans on the radiator and also an LED that indicates when they are switched on, but unfortunately, they still spin due to the wind at speeds of around 70 km/h."

Why not insert a diode with low voltage drop that can handle the current of the fan between the power source and the fan, and connect the LED before the diode? Then the problem would be solved. Alternatively, tap into the control line of the relay instead of the load circuit.

@Gremlin: I'm seeing a maximum oil temperature of 110 degrees in your logs... I get that with my system and constant driving at around 140-160 km/h, which is still well below full load (when it reaches the mentioned 130 degrees).

Do you think the Octavia has a better cooling system, or is it simply due to the measurement location? I'm using a temperature sensor in the oil pan... for you, I would guess there's a sensor in the oil filter flange, which is located after the water pump.

"Hey everyone, perhaps the sensor in the ASZ is located at a different point on the ring, which could cause it to be more susceptible to those short-term peaks?"

Best regards,

Jan.

Okay, just for general information:

I tested my thermostat in a water bath -> it appears to be completely fine.
It opens at approximately 87°C (which is what's indicated on it), and at 100°C, it's about 8 mm open (the minimum dimension according to the repair manual is 7 mm).

What else could be wrong - in case the behavior is actually normal?

Regarding the temperature sensor:
When the engine is cold, the reported values for low-temperature operation (LLT) and diesel are plausible, and at low engine load, the reported +/- 90°C also seem credible.

I consider it practically impossible that its resistance would drop too quickly above 90°C.

Jan6K wrote:

Why not insert a diode with low voltage drop in between, which can handle the current of the fan, and connect the LED before the diode? Then the problem would be solved. Alternatively, tap into the control line of the relay, not the load circuit.

That would significantly complicate my solution.
I only tapped into the output of the fan after-run relay on the EDC, which creates a bypass to the temperature contact of stage 1.
The aforementioned relay is conveniently located inside the vehicle's interior, without any complicated wiring running from the engine compartment to the interior.

@Ulf:

Quote:

Thank you for the data - I think that the ASZ (presumably a type of device) will not have a different thermostat because of the 25 Nm difference.

My repair manual also states that the ASZ engine in the G IV should have a temperature range of 85-105°.

Normally, at 99°, the electric fan usually turns on to level 2 .

Level 1: 92-97° from 84-91°.
Level 2: from 99-105 degrees to 91-98 degrees.

Roger wrote:

At 99°, the electric fan usually switches on to level 2 . Level 1: 92-97° from 84-91°. Level 2: from 99-105° to 91-98°

.
It might be, but my reading of 99.9° is taken at the outlet of the engine block (towards the radiator/heater).
The thermal switches are usually located about halfway up the radiator, where the temperature is likely to be significantly lower.

Hi,

"I also experienced these temperatures with my G4."
I had significant problems with the cooling system, especially when using the trailer hitch. The workshop investigated the issue, and the temperatures actually rose even further without triggering a warning light or causing any movement on the temperature gauge. It was only when I was driving behind a truck that the cooling system completely failed. The outside temperature at the time was around 15°C.
The two cooling fans were replaced because larger engines are required for operation with a trailer hitch.

Thanks for all the answers so far!

I've thought about it again.

The thermostat is located in a "mixing unit" with the cold water inlet and can only maintain a constant temperature there – i.e., at the coldest point in the water circulation system.
In the engine, the water is heated, and it exits the measuring point at a higher temperature depending on the engine load or the amount of heat loss.
Therefore, significantly fluctuating temperatures above the thermostat's setpoint are perfectly normal.

There is a difference of 15°C between the minimum opening and the full opening of the thermostat.
That means the end of the control range is reached only when the temperature in the mixing unit reaches 102°C.
In addition to that, the water in the engine heats up as it travels towards the measurement point.

"In my opinion, temperatures of 110°C seem plausible, and a defect may not necessarily be the cause. And starting at 110°C, the display begins to rise above the 90°C mark."

I'm not going to pursue this matter any further for now.
In August, I'm going on vacation with my Polo, and I plan to take more measurements then, hopefully at higher ambient temperatures.

Do you think the Octavia has a better cooling system, or is it simply due to the measurement location? I'm using a dipstick sensor in the oil pan... with yours, I would guess there's a sensor in the oil filter flange, which is located after the water pump.


Oil temperature measured via an oil level sensor in the oil pan.

I don't know if it has a better cooling system, but it doesn't look like it does.

Here's something else I thought of: the transmission might act as a buffer; that was certainly the case with my old 'grandpa's box' (referring to an older piece of equipment). The transmission oil would initially absorb a lot of heat.
I'll try to find something out in the catalog. Maybe the automatic ALH has a larger oil cooler installed.

CU Gremlin.

Gremlin wrote:

Oil temperature via oil level sensor in the oil pan.

I have one too.
But how can you read the oil temperature?
AI tapped in? -> if yes, which channels