VW Mk2 Golf: Coolant leak from thermstat - andrew4
I have a 1300 VW Mk2 GOLF 1991.

There is a gradual coolant leak from the temperature sensor that is fixed onto the thermostat housing. This was easy to spot as dry pink scale (coolant is pink) comes from here.

The sensor is clipped onto the housing.

Does the sensor need replacing or is it a matter of just replacing a seal?

Also do I have to drain the coolant to replace this sensor?

N.B The sensor could be thermoswitch.
VW Mk2 Golf: Coolant leak from thermstat - Robert Fleming
The sensor doesn't need replacing. Either replace the seal, or clean it up, give it a smear of red hermatite, and replace. You don't need to drain the coolant.

Rob