Weird Temp Gauge issue


Registered User
Apr 30, 2009
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Cape Town
Hey guys - my temp gauge seems to take a while to heat up to 90. When it eventually gets there, it's bang on the mark. BUT, if I'm driving in 5th or 6th - it just drops steadily. Now, admittedly, a lot of the time I drive the car under boost (gas prices, you know) between 2000 - 2500 - but never so that the engine is labouring. It will drop from 90 down to 60 / 70 in a couple of minutes when I'm in these gears. Is it even possible for an engine to cool down that quickly while driving? Or is my gauge / thermostat just fecked?:sos:

2001 s3 btw.

sounds to me like the common thermostat issue mate, I had exactly the same issues you describe. Get yourself a new thermostat for about £15 and get it changed. The temp should be a constant 90 with a fully functional thermostat.
Cool - thanks dude. Glad it's not a bigger engine / cooling problem!:salute:
mines runs at 60 unless it traffic it raises to 90 but goes down to 60 once driving again

yes but hes in South Africa and your in Scotland :)

only joking,yours must be knackered as well.
Mine was doing this , Just changed it and now... 90 all the way.
Its a ****** to get to but if you have plenty of time and some spanner knoledge...
and mine does it as well, how hard is it to replace??

Just did mine this weekend.V easy job. Mine would drop to 60 when moving and i figured it was permenently open.....when i removed it however i found only the top of it remained!!the person i bought it off must have been so tight they couldnt fork out a tenner for a new one and shoved the old lid back in to keep it always open!
I swapped my thermostat today. I had the same issues as mentioned. I used this guide: This DIY is for a Audi TT, but it worked like a charm for my A3 1.8T. (I didnt have to remove the oil dipstick). Make sure you have some extra antifreeze by hand. I lost about 2 litres while doing the swap. Do remember to disconnect the negative pole on the battery. I forgot and sparkes flew :wtf:
Very gooooood guide thank you all, as I have the same issue.
would this effect the fuel economy as mentioned in my other post my emmissions are all over the place and mechanic reckons the temp sender being shagged would not help?????

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