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How Do I Drain the Radiator and Cooling System Flush for '97 and Up Regal/Century

01-11-2009, 08:14 PM
The radiator drain plug/valve is located on the driver's side of the radiator towards the engine. To access it you will have to jack up the front driver's side of car, then remove the plastic splash guard and/or air deflector from underneath the car. Several 10mm bolts may secure the plastic. Once that is removed all you need is a tool like a 1/4" drive socket handle or ratchet. Insert end of tool into square cutout in plug and turn about 1/8" - 1/4" counterclockwise. Coolant will drain.

Note: The coolant may be hot so follow proper safety procedures, let engine cool down and when jacking car up be sure to use jackstands.

The pics below show the tool I use, the drain plug and hopefully should be self explanatory.

If not feel free to ask questions in this thread.

Applicable to '97 and up Buick Regal and Century and '97 - '03 Pontiac Grand Prix
1/4" drive tool and drain plug removed from radiator for illustration purposes
Coolant being drained
Location of drain plug on removed radiator

01-11-2009, 08:15 PM
Here is a cooling system flush procedure using a Prestone brand flush kit.

Install the flush T from the Prestone Flush Kit in the heater return line hose from the heater core per the instructions on the label.

Top Heater Hose = return
Bottom Heater Hose = pressure

1. With engine cool, remove radiator cap and drain the radiator.
a. Turn drain plug (lower left engine-side of radiator) counter clockwise about 1/8 of a turn (may require a little force if it's not been opened in awhile--be careful because it's plastic). Use the end of a 1/4" drive handle. Plug will extend slightly as it loosens. Be sure to have a container in-place to collect the antifreeze.
2. Let all the antifreeze drain into a container.
3. Remove, drain and clean the antifreeze overflow bottle. Reinstall bottle.
4. Hook up a garden hose to the flush T and turn water on (Caution: not too high or you can damage seals/gaskets with the pressure). When water starts to run from the drain plug, start the engine and turn the heater on (make sure you leave the water running during this process).
5. When water runs clear (about 5 - 10 minutes), turn off car, then turn off water, and remove hose from T and cap it. Let remaining water run from drain plug. (Note: Not all of water will be drained out of system mainly the engine block. What I do is hook up a drain hose to the T connector, start engine and let the water pump push water out of the system. As soon as you see no water coming out turn engine off, remove drain hose and cap off T connector).
6. Close radiator drain plug and fill radiator with a 50-50 mix of extended life 5/150 antifreeze/distilled water (or buy premixed 50/50).
7. Start vehicle and bring to operating temperature to make sure thermostat opens. Add additional mixture as necessary until full.
8. Reinstall radiator cap.
9. Release any trapped air in cooling system by turning the plug on the top of the thermostat housing (be careful not to burn yourself). When only coolant (no air) flows from the plug, close it. You may have to repeat this several times to get all of the trapped air. Note: Raising the front end of the car where the radiator is higher than the engine helps bleeding.
10. Add additional coolant as necessary. Also, fill overflow bottle to recommended level. Be careful not to open radiator cap if hot. You may have to do this several times.
11. Check for leaks.
12. Properly dispose of old antifreeze.

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