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ase_master327, Shop Owner
Category: Buick
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Experience:  +15 years experience with Buicks. Bumper to bumper diagnosis & repair.
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How do you replace the thermostat on a 2003 buick century

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How do you replace the thermostat on a 2003 buick century
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The thermostat is on the engine side of the radiator hose that runs to the back (transmission side) of the engine. To get to it you need to remove air duct from the filter box to the throttle body, and the exhaust crossover pipe, that runs across the back of the engine.

Here's how to do it:

Remove the air duct

Then loosen the petcock at the bottom of the radiator .. about 1/4 - 1/2 way (make sure you take off the radiator cap or it won't come out).

OK, now you need to remove the radiator hose from it, and then take off that exhaust pipe that goes right in the way of getting that thermostat housing off.

Then you can unbolt the housing.. see the pretty picture?
So, now you can take off the thermostat, and clean up both sides of the gasket surface. Make sure you clean it up REAL good. A razor blade works great. Then hit it with a wire brush, and some degreaser or something like that.. Just to make sure the surface is completely clean.

OK, when the thermostat goes back in, the part goes inside the engine.. no confusion on this one:
OK, put it on in there, and put it all back together......
I don't usually use any silicone on these. If you get it clean enough, there is no need for it. But that's up to you.

The only special you need to know is torque the bolts for the thermosts at housing to 18 Ft/Lb.

To refill the system.. there is a couple ways you can gho about it...
The best way is to open the bleeder when you go to fill the cooling system back up with the fluid you drained out of it...

If you don't wXXXXX XXXXXce breaking anything, just run the heater while filling it up, and make sure the thermostat is open.. then you can rev the engine up to about 2,000 RPM, and fill it on up.

Just make sure you also have about 1/3 full in the reservoir. And check it again after the engine is warmed completely up, and then after it cools off (when cold only)... check the reservoir, and add more coolant if needed. If it goes completely empty, then you will have to keep checking it until it stops using it up... or fix the leak. It should be about 1/3 full to make up for temperature differences.. it comes in and goes out, ans the engine cools and warms.

If you ned anything else, just let me know! Laughing
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