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This page is taken directly from our digital online manual 24065 for the 1988-98 Chevrolet and GMC C/K 1500/2500/3500 pickup trucks (including 1999-2000 C/K Classics), Chevy Tahoe, Blazer, and Suburban, and GMC Yukon, Yukon Denali, and Suburban, 2WD or 4WD with V6 or V8 gasoline engines, but it applies to many GM vehicles that use 4.3 liter V6, and 5.0 liter, 5.7 liter and other V8 motors. It is recommended that you check the coolant level in your truck and top it up every week, or at the least with every oil change. Draining and refilling with fresh coolant should be done every 30,000 miles or 24 months, whichever comes first. If the coolant appears rusty or contaminated, or your car has no service documentation and more than 50,000 miles, you should flush the cooling system as well.
Cooling system servicing (draining, flushing and refilling)
Warning: Do not allow antifreeze to come in contact with your skin, antifreeze is highly toxic if ingested. Never leave antifreeze lying around in an open container or in puddles on the floor; children and pets are attracted by its sweet smell and may drink it.
Be careful not to spill antifreeze on painted surfaces of the vehicle, as it may damage paint. Rinse off spills immediately with plenty of water.
Check with local authorities on disposing of used antifreeze, even "non-toxic" formulas. Many communities have collection centers that will see that antifreeze is disposed of safely.
Warning: Never remove the expansion tank cap when the engine is warm. Only perform cooling system service after the vehicle has sat for several hours and is cold to the touch.
Periodically, the cooling system should be drained, flushed and refilled to replenish the antifreeze mixture and prevent formation of rust and corrosion, which can impair the performance of the cooling system and cause engine damage. When the cooling system is serviced, all hoses and the radiator cap should also be checked and replaced if necessary.
Apply the parking brake and block the wheels. If the vehicle has recently been driven, wait several hours to allow the engine to cool down before beginning this procedure.
Once the engine is completely cool, remove the radiator cap.
Move a large container under the radiator drain to catch the coolant (see illustration). Attach a 3/8-inch diameter hose to the drain fitting to direct the coolant into the container, then open the drain fitting - a pair of pliers may be required to turn it.
- After the coolant stops flowing out of the radiator, move the container under the engine block drain plugs - there’s one on each side of the block. Remove the plugs and allow the coolant in the block to drain.
- While the coolant is draining, check the condition of the radiator hoses, heater hoses and clamps.
- Replace any damaged clamps or hoses.
- Once the system is completely drained, flush the radiator with fresh water from a garden hose until it runs clear at the drain. The flushing action of the water will remove sediments from the radiator but will not remove rust and scale from the engine and cooling tube surfaces. These deposits can be removed with a chemical cleaner.
- If using a chemical cleaner Follow the procedure outlined in the manufacturer’s instructions on the back of the container. If the radiator is severely corroded, damaged or leaking, it should be removed and taken to a radiator repair shop for repair or replaced.
- Remove the overflow hose from the coolant recovery reservoir. Drain the reservoir and flush it with clean water, then reconnect the hose.
- Close and tighten the radiator drain. Install and tighten the block drain plugs.
- Place the heater temperature control in the maximum heat position.
- Slowly add new coolant (a 50/50 mixture of water and antifreeze) to the radiator until it’s full. Add coolant to the reservoir up to the lower mark.
- Leave the radiator cap off and start and run the engine in a well-ventilated area or outside until it gets warm and the thermostat opens (coolant will begin flowing through the radiator and the upper radiator hose will become hot).
- Turn the engine off and let it cool. Add more coolant mixture to bring the level back up to the lip on the radiator filler neck.
- Squeeze the upper radiator hose to expel air, then add more coolant mixture if necessary. Replace the radiator cap.
- Start the engine, allow it to reach normal operating temperature and check for leaks. Check the level and look for leaks for a few days afterwards to be sure the cooling system is full.