Passat TDI coolant temperature gauge - Jacko
My friend has a Passat TDI 115 and has a problem with the coolant temperature gauge. As the car warms up it just comes on to scale and slowly rises just short of normal temperature then quickly falls back off scale and continues to cycle like this whilst the car is running. Definitely no overheating problems and engine management is OK with no faults. Having checked under the bonnet with the "TDI" cover removed, I can't find the coolant temperature sensor. I would have expected it to be in the cylinder head somewhere.
Any help/experience with locating the sensor please.
Passat TDI coolant temperature gauge - 659FBE
There is no problem with the temperature gauge.

The symptoms you describe are due to an engine cooling system thermostat with too much hysteresis. Hysteresis is caused by stiction in the thermostat operating pin or valve, causing it to operate in "oops, sorry" mode. Replacement is the cure for this.

Passat TDI coolant temperature gauge - Pat L
I put an identical query here a few weeks ago re my Audi A4 TDi 115. (Try a search on 'Audi A4 coolant temperature guage')

I had the thermostat and temperature sensor replaced under warranty (just! car had about a week left.) Fine now.

Is the car under warranty? I'm not sure of the cost otherwise, but I don't think it's a major expense, especially if done at a non-franchised garage.

Pat
 

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