Coolant Temperature Gauge

[jd_hants]

This is a general question about the temperature gauges in Audis. But currently very relevant to my '51 A4 1.8T.

The A4 is losing about half a litre of water a day. I think it's a leak rather than cylinder head gasket. It's going to a garage today!!!

My query: After starting the car (after topping up coolant), the gauge needle goes up to the usual 90 degrees and stays there. After 20 mins or so, the Coolant Temp warning symbol flashes and beeps but the gauge remains at 90. A few minutes later the warning flashes again. But still the gauge remains at 90. In fact, it never drops or rises ever!!!! Is this normal? Surely if the coolant temp symbol appears, it is advising that the temp is too high - so why doesnt the needle rise????

[PetrolDave]

Coolant temperature gauges on Audis are setup to show 90 degrees whenever the coolant temperature is in "the normal range" - to stop owners asking why there car runs hot or cold (according to the gauge). Means the coolant temperature gauge is only able to show you that the coolant is cold, or really, really hot!

[jd_hants]

Ok. so, even though the coolant temperature warning symbol comes, the actual coolant temperature is still within 'normal' range??? presumably if the gauge ever went higher than 90 it would be seriously hot and basically in the 'danger' range?

[PetrolDave]

presumably if the gauge ever went higher than 90 it would be seriously hot and basically in the 'danger' range?

You got it!

[jd_hants]

Thats useful then!!!! Is there any way to use VAGCOM to display the actual temperature rather than the 'heavily filtered' one???

Have you any idea at what temperature the coolant temp warning symbol comes on??? Presumably I'm still ok to drive. Just keep an eye on the gauge in case it leaps to the right, which I also assume can happen pretty rapidly?

[MartynC]

When my secondary fan on my 6 Plus failled and the car overheated on Hardknott Pass in The Lakes, the guage did exactly as Dave described, sudden charge up to full scale deflection along with the overheat symbol. Oil temp guage seems a bit more linear in its indication.

MartynC

[jd_hants]

But the coolant temp symbol had been flashing/beeping way before the temp gauge needle shot up??? What kind of timespan between the two occuring?

[MartynC]

Both at or at least almost, the same time. I'm a bit of an anorack when it comes to these things (aren't we all!) and was watching the guage as we asscended the pass. It's quite a road though so would have been watching outside the car mostly of course, but it all happened very quickly! As you commented further up this thread, very useful!

MartynC

[jd_hants]

Oh ok. MUst have been seriously overheated then. I am getting collant warnings all the time but guage doesnt shift. Must be hotter than normal but not hot enough to trip the gauge!