Is it just me or does everyone have a cr*p coolant temp gauge which never reads right?

It moves up gradually then sits at or just below 90 all the time, despite the coolant temp sensor saying that the coolant temp fluctuates between 70 and 80.

I'm sure I've seen similar posts about this - is it a problem with the instrument cluster or do they "all just do it"?

Makes me wonder if it would move off 90 even if the engine started overheating...

Edited 8 October, 200916 yr by chicken_eyebrow

I think it's only really intended as a 'system healthy' indicator. The temperature of the coolant will vary to an extent depending on how fast you're going, what gear you're in, the time of year etc. etc. and I reckon if the gauge followed the fluctuations that closely everyone would be worried that their thermostats were stuck open... :ne_nau:

mine just sits bang in the middle at 90, unless i leave it stood running then it goes up a bit

This is common to all VW/Audi cars. In my own car, the vagcom readout tends to agree more or less with the temp on the dash. However, the gauge is very heavily damped in order to avoid showing short spikes or dips in temperature. The average temp of my engine (according to vag-com) is always about 90 though so the gauge seems to be working.

On my old Polo the gauge was exactly the same and fortunately did do its job and told me to stop when the thermostat jammed shut on new year's morning. Basically, as long as the damping period of the gauge is lower than the time it takes to increase the engine block temperature significantly it won' be possible for engine to overheat before the gauge indicates that this is happening. This is how the VW sensors should work.

Having said that, on my VR6 Golf, the ECU temp and gauge temp readings were provided by seperate sensors. When the ECU one failed, the car thought it was running at 70 when the dash reported 90 (which was the correct temp as the thermostat was working fine). This meant that the engine ran at the correct temperature (90) but the ECU always set the mixture too rich because it was recieving the 70 degree reading (resulted in 17mpg!). Changed the blue sensor (G62 I think it was) and all was well.

If the vRS uses a similar scheme (I think it might) you might want to check your ECU temp sensor.

Hope that helps.

iep

The pull in range at the normal position is 70 to 100. The guage is non-linear rather than heavily damped. This is intentional and is implemented by the cluster not the sensor. There is actually no mention of 90 on most of the guages. IIRC, the optimal temperature is 88 which is the middle of the range. If you monitor the sensor with VCDS you can see the pull in range and fluctuations that occurs under 'normal' conditions.

I know a few people who have fitted aftermarket temperature guages and have worried that their car was overheating when they are stuck in traffic after a brisk run. This is why most car manufacturers have this arrangement.