Coolant Temperature Sensor

Translated on 19-09-2026, 22:30.

Hello fellow mechanics!

I would like to replace my coolant temperature sensor.
Can someone tell me where it is located?

Audi A3 1.9 TDI
BJ: 99
110 horsepower.
AHF

Best regards.

Bertl.

Translated on 19-09-2026, 22:31.

Hi,

When you're standing in front of the engine, at the right end of the cylinder head, you'll find it. It's secured with a retaining clip and has a connector with 4 pins attached to it.
When removing it, some coolant will leak out, so it's best to have the new expansion tank ready in the other hand; you just have to be quick enough

.

Best regards, Rainer.

Guest Free account, no CAN development support

Let the car cool down for 2-3 hours beforehand, otherwise you might get burned fingers.

Have some coolant and water ready in case the change doesn't go as quickly as expected.

Best regards,

renwal

Translated on 19-09-2026, 22:33.

Great!

Danke für die Antworten. A really great forum.

Best regards.

Bertl.

Translated on 19-09-2026, 22:33.

If the radiator cap is difficult to remove, open the coolant reservoir first (be careful, there may be pressure buildup).
Lightly dampen the (new) O-ring from the supplier with coolant.