As you're facing the rear of the van, follow the upper, left radiator hose towards the back of the van. On the left side of the engine (passenger) that hose will come to a fitting. Follow the hose coming out of that fitting aft and down. It will curl back towards you. That hose goes into the thermostat housing. Disconnect both hoses and remove the first, upper radiator hose. I got about a 1/2 gallon of anti-freeze in a bucket when it's all taken apart. You'll see four bolt heads, two upper and two lower that go into the housing towards the driver's side of the engine. Take those four bolts out (tight fit but can be done with a 3/8" ratchet and 1" extension) with a 12mm socket. There is no gasket on the thermostat housing. It's sealed with high temp RTV. Once the four bolts were out, it took a good smack with a fiber drift and a deadblow hammer to unseat the factory sealant. The following site has a good picture of the whole thing. http://autorepair.about.com/library/a/1g/bl721g.htm
How do you change the thermostat in 1999 Mercury Villager
Do a Google search for it.
Inside the distributor
on my 1999 ford mercury villager its on top of transmission under the van
The thermostat for a 1999 Mercury Mystique is inside of the top water inlet. Remove the top radiator hose from the engine, and then inlet can be removed to get to the thermostat.
Next to the fuses under the dash.
Yes.
If you're talking about the sensor for internal temperature it's in the dashboard next to where the shift lever is.
Under the dash to the right of the steering column.
Attached to the back side of the throttle body.
Under the dash near the fusebox.
According to the 1999 Mercury Villager Owner Guide : ( 20.0 US. gallons )