How-To: 97-05 Century - Buick Forum - Buick Enthusiasts Forums

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Old 07-08-2011, 11:12 AM
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Join Date: Jun 2011
Posts: 33
Default How-To: 97-05 Century

Changing the front or rear turn signal in the 1997 Buick Century requires access to the headlight or taillight assemblies. As an independent mechanic that works on Buicks on a weekly basis, you'd be shocked to learn how many customers take their Centuries to me in order to change the turn signal light bulbs. It's really a simple procedure but here's a quick write-up on the job for those of you who are interested :

4157 NA amber auto replacement bulb (front turn signal bulb)
3057 auto replacement bulb (rear turn signal bulb)
**These bulbs can be bought for UNDER a dollar at and slightly more at a local auto parts store.

1) Open the hood and pull the headlight assembly retaining brackets up about an inch. They are located at the back of each headlight assembly on both the left and right sides.

2) Pull the headlight assembly outward away from the vehicle far enough to reach behind it.

3) Pull the rubber weather boot off the back of the outer corner turn signal bulb.

4) Turn the bulb socket and wire counterclockwise a third of a turn to remove it from the headlight assembly.

5) Pull the turn signal bulb from the socket, holding the socket from its base, and insert the replacement 4157 NA replacement bulb into the socket. Reinstall by reversing the procedure.

**Rear Turn Signal**

1) Open the trunk and remove the three large, plastic wing nuts from the back of the taillight assembly.

2) Pull the taillight assembly outward away from the vehicle.

3) Twist the turn signal bulb socket (in the amber-colored portion of the taillight assembly) counterclockwise to remove it.

4) Pull the bulb out of the socket and push the 3057 replacement bulb into the socket.

5) Reinstall by reversing the procedure.

6) You're done!
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Old 07-27-2011, 10:43 AM
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Join Date: Jun 2011
Posts: 33
Default DIY- Changing the battery on a 2004 Century

Hello again folks,

It's your friendly resident Buick mechanic checking in with a succinct write-up on changing the battery on a Buick Century. The battery sits on the passenger side of the engine compartment just behind the radiator support; be forewarned that space is limited in this area so choose the correct size battery in order to eliminate any fitment issues

--Tools you'll need--
Socket set
Extension bar

--Parts you'll need--
New battery

--The procedure--

1) Open the hood of your 2004 Buick Century and locate the battery on the passenger side of the engine compartment. Locate the negative battery cable on the front of the battery. Loosen the cable clamp's retaining bolt with a wrench and pull the negative battery cable clamp from the battery terminal, and set the cable aside.

2) Loosen the positive battery cable clamp's retaining bolt with a wrench and pull the cable clamp from the battery post. Set the positive battery cable aside. Isolate both the positive and negative battery cables from the battery while you work.

3) Locate the battery hold-down bracket on the front of the battery. It is a plastic wedge located at the base of the battery. It has a single bolt in the center of it that is threaded into the tray below. Remove the battery hold-down bolt using a socket, extension bar and ratchet, then lift the hold-down out of the engine compartment.

4) Lift the battery out of the engine compartment and set the old battery aside. Position the new battery into the engine compartment, orienting it identically to the way the old battery was positioned. Position the hold-down onto the battery and tray, then install the hold-down retaining bolt.

5) Turn the battery hold-down retaining bolt clockwise with a socket, extension bar and ratchet until it is secure. Attach the positive battery cable to the positive battery terminal with the cable clamp's retaining bolt, turning the bolt clockwise with a wrench to secure it.

6) Attach the negative battery cable to the negative battery post using the clamp's original retaining bolt. Tighten the bolt by turning it clockwise with a wrench. Test the installation by attempting to start the car. If it starts, the repair is successful. If it doesn't, then check the terminals and other pivotal battery components to make sure that everything is hooked up properly.
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Old 08-10-2011, 10:55 AM
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Join Date: Jun 2011
Posts: 33
Default How-To: Replace the Radiator on a 2005 Century

Hello Century connoisseurs!

I've had the pleasure of working on a 2005 Century a few days ago and I wish to share a succinct write-up regarding radiator replacement on this fine auto mobile. The entire job takes about 5-6 hours, depending on your mechanical skill level. And with this walk-through, all that you have to spend money on is parts and possibly tools

Use care when working underhood around the cooling fans. The fans are controlled by the Powertrain Control Module (PCM) to come on at a certain temperature, even with the engine turned off. Always disconnect the negative battery cable to prevent the fans from starting without warning.

--Useful diagrams--
2005 Century Radiator diagram To view the diagram: click 'Get Info' button under Parts Listing tab, click the 'Go' button in the window that pops up and the diagram will be displayed.

1) Disconnect the negative battery cable.

2) Drain the coolant from the radiator.

3) Remove the engine mount strut. Some technicians will disconnect just one and swing the strut out of the way. In this case, loosen the through bolts to prevent shearing the rubber bushings when the strut is moved out of the way for radiator removal. In some cases, it is best to remove the strut and its mounting bracket completely.

4) Separate the cooling fan harness connector from the engine harness.

5) Separate the low coolant level module harness connector at the module.

6) Disconnect the radiator hoses.

7) Remove the cooling fan assembly from the vehicle.

8) Disconnect the automatic transaxle cooling lines from the radiator

9) There should be two small retaining brackets at both ends of the radiator that are removed.

10) Carefully lift the radiator up and out of the vehicle. Note that the bottom should have locating pins on each end which should fit into grommet-like rubber mounts at installation.

11) Use care when handling the radiator. It is constructed of aluminum and should be handled carefully. Install the radiator, making sure that the lower locating pins on each end fit into the grommet-like rubber mounts.

12) Connect the transaxle cooling lines to the radiator.

13) Assemble both the cooling fan harness connector and the low coolant level module harness connectors.

14) Install the remaining components in the reverse order of the removal process. When refilling the cooling system, use the proper mix of coolant and water. Check for leaks.
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Old 08-24-2011, 11:25 AM
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Join Date: Jun 2011
Posts: 33
Default How-To: Replace the Thermostat on a '05 Century

Hello again folks!

It looks like this forum is beginning to become more active In light of the increased activity, I have decided to share a How-To article with you guys that documents the procedure for changing the thermostat on a 2005 Buick Century. Please note that this guide will also apply to model years 1997-2004:

1) Disconnect the negative battery cable.

2) Partially drain the cooling system into a suitable container, to a level below the thermostat.

3) It is usually possible to leave the radiator hose attached and simply remove the thermostat housing (also called a water outlet) and flex the radiator hose enough to service the thermostat. It is good practice, however, to remove the radiator hose so the thermostat housing can be given a thorough cleaning. Debris on the thermostat housing sealing surface can cause leaks.

4) Some applications may have electrical connections to sensors which mount in the thermostat housing. Use care when detaching these connectors.

5) Unfasten the thermostat housing bolts and remove the housing.

6) Remove the thermostat by simply pulling out. Discard the gasket.


1) Clean all parts well. Make sure the sealing surfaces on both the thermostat housing gasket flange and the intake manifold are clean and free of corrosion damage. It is good practice to run a thread cutting tap or a clean bolt into the threaded holes in the manifold to clean out old sealer and dirt. The threads should be clean so the thermostat cover clamps the gasket evenly at assembly.

2) Position the thermostat in the intake manifold. Make sure it is seated.

3) Position a new gasket over the thermostat. If no gasket is used, apply a 0.125 in. (3mm) bead of RTV sealer to the thermostat housing and install the housing. Lightly lubricate the bolts with clean engine oil. Torque to 18–20 ft. lbs. (23–27 Nm).

4) If removed, attach the radiator hose to the thermostat housing.

5) Refill the engine with the proper mix of DEX-COOL®and water. Connect the negative battery cable, start the engine and check for leaks.

**Additional Reference Material**
2005 Century Cooling diagram <--Click on the 'Get Info' button underneath the Parts Listing tab, then click 'Go' in the window that pops up and the diagram will be displayed.
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Old 10-25-2011, 01:42 PM
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Join Date: Jun 2011
Posts: 33
Default Write-up: Replacing the Fuel Pressure Regulator on a '05 Century

Hello again all,

I'd like to post up an insightful article documenting the procedure for replacing the fuel pressure regulator on a '05 Century Enjoy!

1) Disconnect the negative battery cable.

2) Relieve the fuel system pressure.

3) Remove the upper intake manifold assembly.

4) Disconnect the vacuum line from the pressure regulator.

5) Remove the regulator retaining screw and remove the retainer bracket. Using a clean shop cloth to catch fuel spillage, carefully pull the regulator from the fuel rail. Twist the regulator slightly while removing to ease removal. Discard the O-ring.


1) Clean all parts well. DO NOT use shop compressed air to test or clean a fuel pressure regulator. Clean the fuel pressure regulator screen, if necessary. DO NOT immerse the fuel pressure regulator in a solvent bath or it will be damaged.

2) If the filter screen has been contaminated, it should be removed and the pressure regulator replaced.

3) Lubricate a new pressure regulator O-ring with clean engine oil and install on the regulator inlet.

4) Install the fuel return pipe to the regulator.

5) Install a new retainer and spacer bracket into the slot on the fuel rail and install the pressure regulator to the fuel rail. Tighten the fuel return line nut to 13 ft. lbs. (17 Nm).

6) Connect the vacuum line to the pressure regulator and install the retainer screw. Tighten to 76 inch lbs. (8.5 Nm).

7) Inspect and verify that the retainer and spacer bracket is engaged in the slots in the fuel rail. Grasp and pull on the regulator to ensure that it is properly seated.

8) Install the upper intake manifold.

9) Connect the negative battery cable.

10) Inspect for leaks using the following procedure:
  • Turn the ignition switch to the ON position for 2 seconds.
  • Turn the ignition switch to the OFF position for 10 seconds.
  • Turn the ignition switch to the ON position again.
  • Inspect all areas for fuel leaks.

*diagram courtesy of; all rights reserved
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Old 11-29-2012, 12:54 AM
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Join Date: Nov 2012
Posts: 1
Default How do I change the rear bulb around the license platge

Please give me detailed directions on how to relplace the bulb in the rear that goes to the license plate. It's a $130 fine and I have been pulled over 2xs and have the bulb, just need to know how. Thanks for any help on how to get the plastic off without cracking it???
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Old 12-25-2012, 09:07 PM
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Join Date: Oct 2011
Location: Northern Ohio
Posts: 402

Once you open the trunk there are black butterfly plastic screws that you spin of to get the tail lights off. There is about 7 or so and once you get them the license plate lights are a simple twist. If I was at my parents, I could take a pic of the broken set but it's pretty easy once you have it off the car and see it. Will come by later to modify this into "How-To" form.
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Old 08-11-2013, 10:36 PM
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Join Date: Aug 2013
Posts: 17

i need help with trying to figure out why my cooling fans stopped coming on. it all started a few years ago when they stopped and turned out the fans were bad, bought a new used set on ebay. After installing they worked and kept the engine cool, recently after doing some work to fix a leaking timing cover( was a bad gasket, bought used cover from JY) and bolted everything up runs good, but when temp gets to half way to lil past there supposed to come on but didn't. with my lack of electrical expertise i tested the relays and the fan motors one relay was bad. Changed it with still no fans, read online that it could be the CTS coolant temp sensor, changed that still no fans coming on. been looking for a wiring diagram for the cooling fans so i can check to see if theres any cracked or loose wires.
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Old 04-02-2015, 09:14 AM
Join Date: Mar 2015
Location: Springfield, MO
Posts: 37

I'm posting to subscribe to this.
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