1.4TDi Temp Gauge above 90°C


New Member
My temperature gauge has always been rock solid at 90°C once warmed up regardless of driving condition (motorways or in town).
I've recently had a cam belt change as I was unsure when it was changed last (Odo 186,000) and had the water pump changed at the same time as a precautionary.
Last month the Temperature sensor went erratic and either displayed 60°C or normal, so I had the sensor swapped out and the thermostat.
The temperature upto a week ago was 90°C, now it modulates between 90°C and 100°C.
The temperature seems to be ~100°C when i'm on the motorway and cools slightly to "normal" when I get onto slower roads. This is confusing me as I would think that sitting in 5th gear at ~3000rpm with a lot of air over the radiator would be cooler than up and down the rev range in slow traffic.
There are no signs of coolant loss or leaks around the hoses or expansion tank, heater works fine, the oil cap is mayonnaise free and the coolant maintains it's level and clear pink.
I'm not too concerned as the temperature never exceeds 100°C i.e. within range, but I'm curious about the underlying reason for this sudden change in temp behaviour and whether it's symptomatic of something more sinister.
Any ideas??


New Member
Thanks for the replies. I believe, like most non-dealer workshops that the part was an OEM rather than an AUDI stamped part.
Is it being suggested that that the new part was working initially and has now partially failed, ie not opening fully but operational?


A2OC Donor
Take it back to the garage and have them fit another thermostat and temp sensor. Could be either or could be both are faulty or installed wrong. Best to fit genuine sensors and stats for this very reason.

I have seen the thermostat fitted back to front before.
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New Member
Well wadda-you-know??.
Swapped out the thermostat, probably another OEM part and the temp is now solid at 90°C once warmed up.
So I guess the old thermostat was bit sticky or it's "calibrated" opening point was a bit generous.


A2OC Donor
I think the consensus on here from many, many bitter experiences is:

ALWAYS fit genuine Audi thermostats and engine sensors (not just temp ones!). And even then, you don't always 100% sort the issue (i had a duff genuine thermostat that didn't work right from out of the box).


A2OC Donor
Add in that there is now a large amount of fake goods out there stamped and correctly marked as genuine. Really is a case of buy those parts from the dealer and any issues they will sort it out. Lets hope the dealers keep stocking these items.


In fairness my car came with the cheap circoil stat and worked fine for a few years until one day the car would barely get above 60, removed it to find one of the fingers from the stat housing jammed in it, hardly the stats fault!
Fitted a genuine unit as I had one in stock and all seems fine!