So....basically I had water gushing out the top of the expansion tank. Replaced that two-pronged sensor in the top which had completely broken off with a new one but the water still leaked out of the top around the sensor. Broke that new sensor trying to tighten it too much, now put a whole new expansion tank in and another new sensor.
Still have water leaking around the sensor. As far as I'm aware everything is working ok, water is circulating and returning, electrics seem fine etc.
Is this something blazingly obvious I just can't see? Much as I like keeping sensor manufacturers in business I'm sure all the coolant it dumps down the road can't be good for the engine!
The Golf is a mk2 gti registered latter 1988.
Any help is much appreciated, cheers!