Perhaps plugged radiator - have it boiled out or replaced
The thermostat controls only the temperature of the water.
im not very knowledgable with volks but there may be a water pump problem, or a radiator problem,is the radiator circulated the cool water from iit to the block that has hot water in it?
Bad water pump , problem with engine cooling fan ( if it is actually running hot and not a problem with the gauge or sending unit )
If water is coming out around the thermostat housing, the seal or gasket is bad.
sounds like you installed new thermostat upside down if that's not the problem, you have wrong or faulty new thermostat to test thermostat out of vehicle, place in pot of boiling water and watch to see if thermostat opens
Cracked.head
That depends on the thermostat. If it's a 185 thermostat, the engine should run at 185. If it's running too hot, check the thermostat, radiator and water pump. If it's running too cold, replace the thermostat.
low on water or bad thermostat
in the water pump
Thermostat and radiator
the thermostat is located just behind the water pump . follow your bottom hose
Could be a bad water pump.