Where do I locate the thermostat on the engine of a buick century 2003

I am assuming you have a 3.1 v6 engine the spark plugs are 3 right in the front next to the oil dipstick and above the exhaust manifold you can follow the wires from the coil to find each plug. The other 3 are on the back side of the engine and can be difficult to get to. Easiest way is to remove the upper engine mounts and tilt the engine forward a few inches with a ratchet strap or something to gain clearance. MAKE SURE it is secure because your arms will be back there. And those three plugs are in the same location as others just on the opposite side of the engine.again just follow spark plug wires down to the plug.

I am assuming you have a 3.1 v6 engine the spark plugs are 3 right in the front next to the oil dipstick and above the exhaust manifold you can follow the wires from the coil to find each plug. The other 3 are on the back side of the engine and can be difficult to get to. Easiest way is to remove the upper engine mounts and tilt the engine forward a few inches with a ratchet strap or something to gain clearance. MAKE SURE it is secure because your arms will be back there. And those three plugs are in the same location as others just on the opposite side of the engine.

Go to You Tube Video & watch

If there is a bleed valve near the upper radiator hose, you can use that.
If not, you would have to run the engine with the cap loose until the thermostat opens to let the air escape.

Locate the upper radiator hose. Follow it to the engine. Before it meets the engine, you'll notice that its clamped to a metal housing, usually mounted with 3 ten-millimeter bolts. This is the thermostat housing. Remove when engine is cool. Thermostat is inside. Remove old thermostat and replace ensuring the rubber o-ring aroung the outside of the thermostat if equipped. Good luck.

A 1986 century, you forgot to list then engine size so i will guess its a v6 engine, if its a four cylinder just follow the top radiator hose to the engine and the same goes for the v6 engine, the housing that the top hose clamps to at the engine is where the thermostat is locted,

Find the thermostat on all vehicles like this:

The engine end of the upper radiator hose goes over a pipe stub, or nipple, and then has a hose clamp tightened around it to hold it on that part. That part is a housing, bolted to the engine, and the thermostat is under that housing.

Change the thermostat under the intake horn.

i would think your engine coolant thermostat is stuck open or faulty and needs to be replaced, inexpensive.

Fllow top radiator hose from radiator to engine, where hose clamps on engine is called a goose neck thermostat is under that, it will be held on with 2 bolts. are you sure you got all the air out of system when you chg. water pump? If you don't bleed all air out of system it will not blow hot, because of an air pocket in cooling system.