my mothers car has somehow gotten green antifreeze mixed in it and there is orange gunk in it.

will a simple water hose flush be sufficient or should I take it to a shop and have them flush it and put in mixes with all colors?

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2000 ssei gone but not forgotten

Current fleet:
2009 G8 v6, 2009 Avalanche LTZ, 2013 Volt

Drain what you can out of it. Refill with water. Run it for about 30 mins, then drain. Refill with water again, but add Prestone radiator cleaner this time around. Drive around for a few days, then drain. Take a good look inside the radiator to see if any gunk remains. If so, retreat with the cleaner again and drive another few days.

You'll never get all the sludge out the first time in. It takes time to build up, it'll take time to break it down.

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2005 GXP - White Gold Pearl, no mods...yet.
2000 SSEi - Resurrection in progress. Built L67 w/L32 fuel rail, ported heads, and cam. Camaro front brake system, GXP cluster, and much more in planning.