General Motors — Replacing coolant and cleaning the cooling system
Maintenance
From a General Motors operator's manual covering: 4.3L 262 CID, 4.3L V6, GMG-643. Check it applies to your exact model before use.
Before you start
- Use soft water; well water or river water may cause scaling or rusting.
- Wipe away spilt fuel.
- Retain and properly dispose of old fuel and oil to prevent pollution.
Procedure
- Open the radiator cap and open the drain cocks of the engine crankcase and radiator to remove the coolant.
- Close the drain cocks and pour coolant into radiator; run the engine until the coolant is heated to about 80 C.
- If there is considerable scale or rust pour in a cleaning solution and run the engine until heated to about 80 C.
- Continue to idle the engine for about 30 minutes.
- After stopping the engine open the drain cocks and drain off the coolant completely.
- Close the drain cocks and pour in coolant to rinse the system thoroughly until dirty water no longer runs out.
- Use soft water and fill until it flows out from the overflow pipe.
- Run the engine for a while then stop and check/replenish the coolant level.
Specs & values
- Heat coolant to 80 C or higher
- Idle about 30 minutes
Source: General Motors operator's manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.