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Flushing Coolant From LS Engine block

5.8K views 5 replies 4 participants last post by  Flynman  
#1 ·
What is the best way to completely flush coolant from an LS engine block? I had put dexcool antifreeze in it and only ran the engine for a few minutes. Have been reading that the Dexcool can cause potential problems and most guys seem to be switching back to the Prestone Green. I had to take the radiator out to weld a bung onto it so i flushed that out real good and drained some of the block from the hex plug on the drivers side of the block. Heater system hasn't been hooked up so thats still clean.

Thanks,
Keith R
 
#2 ·
I think you would want to run plain water through it putting it in at the outlet on the water pump. But I don't know a specific procedure - surely one exists. BO185 will probably have a suggestion. Or just try Google.

I know Dexcool is known for its problems, but it's done well in my '09 truck.
 
#3 ·
There's a block drain plug on each side of the engine
 
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#4 ·
I was curious because i went on LSTech forum and there were some pretty elaborate explainations on how to do it "Properly" . Some seemed pretty excessive. I think opening the side engine drain plugs and flushing it through the top radiator hose will probably do the trick. Sometimes internet research leads to confusion!
 
#6 ·
I wound up running water into the upper radiator hose and opened the 2 side plugs on the engine to flush it out. There wasnt much DexCool in there so it didn't take much water for it to start coming out clear.