Originally posted by: Electric Amish
Are you sure it's the thermostat.  I've been looking at some Passat forums and it seems that the temperature sending unit is a known bad part.
		
		
	 
I know that it works, cuz the car still boils over occasionally.
What happens is the car heats up to around 250f then the thermostat opens up and it cools to 240, then back up to 250, then down again. If I put any stress (ie driving up a hill) other than just driving around town, it over heats. I'm thinking the shop that replaced it put it in backwards, or my water pump is going out. I don't really want to replace my water pump, so I just want to either a) check the thermostat and make sure it isn't turned around, or b) just yank the thermostat out for the summer. 
Edit:
I've checked the hoses to make sure they're not collapsing, too... they're fine.
The car doesn't have a regular radiator cap, so that's out.
I know that VW's like to run hotter than other cars, but this is too hot.