I'm still struggling to get this problem resolved. I have a 1991 Jetta (wolfsburg) and when the car is idling the coolant boils over. The thermostat, fan switch and relay have been replaced. The fan comes on but does not spin as fast as it used to. It still pulls heat away but obviously not enough. When I drive, the temperature sits in its normal range. Looking into the reservoir, the coolant appears to be circulating properly. Tail pipe emmissions are fine (ie no white smoke). Is it the fan motor itself? Head gasket ?
Any suggestions?
Thanks in advance.