Proper Coolant Temp?

I have long heard that the temp gauge in the dash is only approximate. I can confirm that since the gauge is solidly on 190, while the recently added P3cars gauge says the normal operating temp is around 205 F. This is in the 2013 Passat.

Should I be worried that this temp is too high?
The coolant level is fine.


Mods- I figured this is a fairly general question. If it should have been in the Passat NMS section feel free to move.

That's a pretty typical running temperature. Nothing to worry about - it tends to move around a bit depending on engine load too. For instance it'll always read higher when accelerating up a hill; the sensor is measuring the exit temperature at the head so it'll always show some effects of engine load.

Essentially this is why VW started putting fake gauges in - folks were always wanting to "fix" something that isn't broken.

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I've seen the temp go up to as high as 210 while climbing hills.

If this is reasonable, then how high is too high?

225-230 is where I'd be concerned personally. I think the fan comes on around 210F.

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Thanks for the information. I wasn't sure if I should be worried or not.

So I'll do as everyone says, "drive more, worry less."

You may even see it higher during regens and such.

Interestingly, there have been a few Threads relating to the TDI engine cutting-off fuel when coasting in gear (which is correct).

Anyway, back in the day, my commute to work involved a section of road that's about 4.2 miles totally down hill and curvy. Well, on very cold (below freezing) mornings, I would let the car coast in gear (got a little slow in a few places) the entire 4.2 miles. During the coast, the Fake Temp gauge would actually drop off 190 considerably... instead of straight up, it would drop to about 9:30 to 10:00 O'clock position.

So, it is not totally Fake, at least not on the low end~!

It isn't fake it just doesn't move until you exceed some limit above or below 190. Then it starts moving like you would expect.

Indeed, the gauge is "incorrect". It will show 90 *C (while actually being anything between 70 *C and 115 *C). If the coolant temperature exceeds about 115 *C, then the gauge will abruptly move the needle towards "overheat" section along with coolant light.

This behaviour can be fixed but... It will require very expensive equipment in order to dump the EEPROM, do the required amendments and push it back, leaving alone the entire operation is very risky; you might end up with bricked cluster which the oly way to remedy is to throw into the trash bin. Is it worth? You decide it.

After I put my scan gauge in I noticed that the temperature gauge on my MK4 starts to move at 120 F and reaches straight up at 164 F. I have seen it go as high as 213 F and still not move any further.

My daily commute involves a 7% grade 10 miles long. Down in the morning, up in the evening. In winter coasting downhill the temp gauge can go all the way to cold and the scangauge can drop to 60C. Uphill in the summer, speed limit 65mph, The factory gauge reads 190 always but I see up to 106C on the other gauge.

Tdijarhead said:

After I put my scan gauge in I noticed that the temperature gauge on my MK4 starts to move at 120 F and reaches straight up at 164 F. I have seen it go as high as 213 F and still not move any further.

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Pretty much exactly as I've seen on about 7 (?) MklV cars I've owned and monitored by ScanGauge, TDI and 1.8T powered.

i have a scanguage II and it tells me in real time what my coolant temp is and the cluster temp gauges is WAY off and is 100% useless aside from saying you can turn on the heat in the winter.

I highly suggest getting one.

i never saw anything past 107 but recently i can get it to 135 if im not careful but thats because i have headgasket issues from running 31 psi and too much timing.

Henrick said:

Indeed, the gauge is "incorrect". It will show 90 *C (while actually being anything between 70 *C and 115 *C). If the coolant temperature exceeds about 115 *C, then the gauge will abruptly move the needle towards "overheat" section along with coolant light.

This behaviour can be fixed but... It will require very expensive equipment in order to dump the EEPROM, do the required amendments and push it back, leaving alone the entire operation is very risky; you might end up with bricked cluster which the oly way to remedy is to throw into the trash bin. Is it worth? You decide it.

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It isn't incorrect as it is operating as intended. It was never meant to show a degree by degree temperature.

Lightflyer1 said:

It isn't incorrect as it is operating as intended. It was never meant to show a degree by degree temperature.

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No., the opposite. It is intended to be made to have the error to prevent people from flooding dealerships with such requests as a) my car isn't warming up [if the driver is using cabin heat, naturally coolant temperatures are lower and the car barely warms up]; b) my car is overheating [driver is going uphill, towing or in very hot climate].

I have modified my cluster's firmware so mine is within 1 degreee with G62 readings.

Well, that may have been the design and intent of the VW temp gauge, but I can say with certainty that the Temp Gauge in my 22 year old Chevy Blazer moves with the temp change. Seems the increments are either 2 or 2.5 degree increments (Fahrenheit). It never stays put in one spot during operation.

Also, the Temp gauge in my RV has a transitioning sweep from green to yellow to red. Once fully warmed up, the Temp gauge does vary within the yellow (normal operating range) depending on the operating conditions.

I know I am old and have been at this too long, but I remember in the early days of watercooled VWs, especially the Dasher the gauges were very accurate. In the case of the Dasher the gauge would climb almost, and sometimes into the red before the fan came on. It was indicating exactly what was happening, and many many people complained. I got tired of explaining that it was normal in that car.

Honda in the first gen cars had a wider range on the gauge than later versions and people complained too. One year they changed gauge calibration and nothing else and people would comment about how cool and efficient their car ran, as opposed to the worries the model before.

Having been on the receiving end of overheat suspicions, I very well understand the gauge logic now applied by VW and other manufacturers.

It is a visual non check engine temperature gauge. I had a 1984 Peugeot STD and the temperature gauge moved a lot. Now in the consumer market people do not understand thermostats so VW just put in the algorithm to say 90 degrees C unless cold or hot that you should pay attention.