Temperature gauge creeping past 90
 

Whilst sitting in traffic coming back from church on Sunday I noticed the temperature gauge creep past 90 and settled at around 95 for quite some time before moving up to 100.

Is this normal? I've never seen this before as it's always been stuck on 90, but Sunday was ridiculously hot in London.....and I had the air conditioning on if that makes a difference?

A genuine thermostat was put on about 9 months ago along with timing belt etc etc, so that is probably OK.

The coolant was flushed and replaced the same time as the timing belt so that's ok too. Could the rad need replacing? The fan was also kicking in, but what temperature should it activate?

Do you think this is an issue or just the effect of the searing heat we're getting? Maybe some of you guys have the same with your 8's

The fan cuts in at 94degC iirc. Apart from the high ambient temps, given the work you have had done I cant see what may be causing the issue.

VW / Audi's will display a fixed 90c on the gauge when the actual coolant temp is between a range. So you can't tell the true temp from the instrument cluster. Have you VCDS or OBD11? These will be able to read the true coolant value.

I don't know at what temp the rad fans will kick in on the D2, but on a D3 it's 100c

Mine used to go over 90 when sat in traffic or slow moving when it was hot outside. Personally i wouldn't worry about it until it got to 120 and i'd be shutting it down on the mark between 120 and the red mark, if it wasn't starting to cool before that. I know others would play a lot safer and shut down before then.
I always used genuine coolant. Was it genuine coolant used when it was filled up?
Don't worry about the fan coming in, at least you know it's working and doing it's job.

OK, thanks for the reassurance chaps - I could just be panicking over nothing. It's certainly driving and behaving as normal.

The coolant was genuine Audi stuff so nice and pink :D

The D2 viscous fan is obviously always running but the electric fan cuts in at 94degC. I had an overheating issue a few months back and sat and watched the displayed temp and noted when the fan cut in. Later I monitored with VCDS which, as stated, is a very useful tools here and there was a reasonable alingnment with the displayed temp. The 'stat should start opening at apprx 87DegC and be fully pen at 102degC.

I am having the same issue. Although I have a known bad coolant temp sensor, so that could be it in my case.
I thought the viscous fan needs to engage at certain temp? Its always idling but not full force until the clutch engages. I remember there was a simple check to test it, if you can stop it with a pen then the clutch hasnt engaged.

Just to add, from experiences with my previous S8 it should not overheat even in really hot weather. I took that one all over Europe, down to Morocco, and to central Spain when temps were over 40C, the gauge never went past 90. So to my mind something is not quite right with my current 8

And if it takes your hand off it's working :lol:

Couldn't you test it just as easily (but perhaps a little more safely) without the engine running? If the engine/coupling is hot, I would imagine the fan should be difficult to turn, should it not?

Well, everyday is a learning day. I hadnt appreciated the potential issues with viscous fans and the temperature sensitive clutch engagement mechanism. I found this article helpful:
http://www.freeasestudyguides.com/pe...an-clutch.html
The failure of the viscous fan mechanism could be your issue.

On my last 8 I knew the viscous fan was gone because it sounded like an old Mitsubishi shogun when up to temp and constantly runnIng.

I plugged in the my OBD11 dongle earlier and cycled through the sub menus. I didn't realise there was something for coolant temps :rolleyes:

anyway on idle and up to temp, the gauge indicated 90 degrees but was actually 99 degrees according to the app. When driving the gauge remained at 90 but the app indicated the car was running between 103 to 104 degrees. It spiked at 105 but then went down to 104 again. The whole time the gauge remained at 90 :Confused:

Nothing wrong there, that's how VW/Audi designed it. The engine can work within a specific temperature range. So owners don't get worried with a constant moving temp gauge they fixed it at 90c when it's within this design range. So for it to move to 95c is odd. Worth keeping a check on but could be down to the recent hot spell.

Experienced as I am in driving my car in 40°+ temperatures, I can say that the temp gauge on the S8 will rise very slightly above the 90 mark on extremely hot days (35°+), but only in traffic or at low speeds.
Moving at good pace, the speed settles and stays on 90°, even at 42° (the highest temperature I've driven in since owning the S8 - some mild summers recently :p).

With the climate control on automatic (ie. Aircon on), the aux fan runs at slow speed constantly (nearly inaudible). It will turn off on Econ mode and then run purely on temp settings.
The trinary switch will of course trigger higher fan speeds as the engine temperature rises, which may be the 'trigger' David is hearing at 94°.
Different markets may trigger this differently of course, though I don't see why they'd bother when you could potentially drive it to a hotter climate...

Thanks all for your input.

I'll definitely keep an eye on it and report back if anything changes. I may look to change the coolant temp switch as a precaution too.

Lol, I did say use a pen :)
Yes I agree not necessarily the best test, I read it on the internet.

I'm going to check my fan and report back.